RSS Feed for This PostCurrent Article

Cleaning Slate – Expert Advice on Cleaning Slate and Slate Floors – Part 1

Cleaning slate isn’t too difficult. It’s vital, however,to know what kind of dirt or contaminant you are trying to remove before you can make a decision as to which cleaning product is best suitable.

Slate comes in many different colours and finishes. Some of these are smooth whereas others have a textured surface. Undoubtedly, slate is a very popular material for flooring right now.

Slate generally has good resistance to mild acids so this gives you a much wider choice of cleaning materials than you would have with more acid-sensitive stones like limestone or marble.

So, how do we go about cleaning our slate floor?

First, you need to check whether the contaminant is mineral based? e.g. grout staining, cement, rust or general dirt. If it is, you would be advised to use a mild acid cleaner such as one based on phosphoric acid. Beware though as any acid cleaner may etch the grout also.

In most other situations where you have, for example, general dirt and grime, wax, oil or a general build up of old polishes etc. I would recommend using a strong alkaline cleaner for periodic intensive cleaning. For everyday cleaning I’d recommend using a mild, neutral cleaner.

Here’s an Expert’s 6 – Step Guide to Cleaning Slate:

1. Ensure your slate is protected with a high quality sealer: either an impregnating sealer which will give you a natural look with a mat finish and below surface stain protection. Or, if you prefer the look of wet slate, in so far as the darker colours, but still want a natural, mat, no-sheen finish, then look a good quality enhancing sealer such as Enhance ‘N’ Seal. Alternatively you can use a coating sealer for a pleasant low sheen gloss which really helps any ongoing cleaning.

2. You must eliminate all grit – this is the major cause of all wear to slate floors. Ideally, place a dust mat both inside and outside the room which will help remove grit from shoes and prevent it from spreading to the slate floor.

3. Sweep and vacuum the slate floor regularly. This will also help remove grit from the surface of the floor.

4. Mop up and soak up isolated spillages as they happen. You shouldn’t leave strong contaminants such as coffee or wine to dwell on a slate floor.

5. Wash the slate regularly intervals using a mild, neutral cleaner. This will clean the slate but it won’t damage the stone, grout or the sealer used.

6. Less frequently, carry out a deep clean. For this, we recommend using a high alkaline cleaner. More in Part 2.

Update 22/01/13 – Check out this case study on cleaning slate




Copyright Ian Taylor and The Tile and Stone, 2013. See copyright notice above.

Trackback URL

RSS Feed for This Post289 Comment(s)

  1. Glyn | Aug 21, 2009 | Reply

    I have a grey / white stains appearing on a number of my slate floor tiles (textured grey/blue/black mix). Some were appearing before I stripped it & more have appeared afterwards. Mainly around the edges but also some in the middle of tiles. I have recently stripped it with Plasplugs tile polish remover(which I had used succesfully before) & then impregnated & sealed with HG products – again used before. Any ideas on what I need to do to remove the stains? I have a patch of the floor that I have not impregnated & sealed which also shows this marking.
    Your help would be appreciated as I love my floor but am concerned I have done something bad to it!!!!

  2. gwyneth | Mar 11, 2010 | Reply

    I have slate hearth that came off a snooker table it has brown streaks that wont come off could it be rust and how can i remove them

  3. Ian Taylor | Mar 11, 2010 | Reply

    Hi Gwyneth,

    It is hard to advise without seeing the slate. Some slates do have other minerals in them, including sources of iron, so it is not impossible for slate to have rusty veins within it. If this is the case it may be impossible to remove as it is part of the stone. However, if it is a rusty deposit (perhaps the slate was stored somewhere for a while and something metal was lying against it for example) then it should be removable.

    Acidic cleaners are frequently used to remove rust, you could try Extreme by Aqua Mix – just pre-wet the stone, pour some neat Extreme onto the stain, leave it to dwell for a minute and scrub. Remove and rinse. – Do you have any pictures you could send me? – Might give me a better idea of the problem.


  4. Ross | Sep 8, 2010 | Reply

    I have some slate tiles installed on the walls of my shower enclosure but one of the tiles is rusting and I have noticed rust streaks / stains running down the wall and slight staining on the floor of the shower tray as a result. Any ideas how I can prevent this and clean the stains? I sealed the tiles when they were installed a year ago with about 4 applications of sealant. Thanks. Ross.

  5. Ian Taylor | Sep 8, 2010 | Reply

    Hi Ross,

    OK, first let’s get the obvious out of the way; Is the rust coming from a metal fitting of any kind, like the shower outlet or slide rail for example? – If so then you have to take that down and treat/replace that.

    However, some slate can create rust all by itself; within the slate there may well be some form of iron-bearing mineral, we see this a lot in the autumn and multi-coloured slate, as well as in granites and marbles, limestones and other rocks. All that is needed is some moisture and oxygen to oxidize the iron and you make rust. So the question is, is there some moisture getting into the slate? This could be through an ineffective seal (not so likely with 4 good coats as you say, although sealers are not waterproofers, they are stain resisters). Maybe there is another reason, something leaking behind and finding its way to that part of the slate, or fine cracks in the grouting, fine gaps opening up between the grout and the edge of the slate (over time with movement, no sealer will prevent this).

    So have a good look, see if you can identify the source of the moisture – anything obvious – fix that first. Also bear in mind that impregnating sealers are not coatings, they will not put a barrier between the surface of the slate and the water (they are inside the slate as a stain barrier). So any iron in the actual surface will be exposed to the shower water and the problem could be that simple.

    To remove it, use a mild acidic solution, preferably one based on phosphoric acid (they use this in the motor trade to remove rust from metal) so Aqua Mix Phosphoric Acid Cleaner or Substitute or for a larger problem, Aqua Mix Extreme is excellent. If it is coming from the surface of the slate then it will re-occur – just keep cleaning it until it stops, you may consider a coating sealer to add a bit of a barrier a the surface but even this may not prevent it 100%. If the problem is from some underlying leak then you have to get that fixed and then it should not reoccur.

    Hope that helps


  6. Jean Saunders | Nov 16, 2010 | Reply

    I have just had a new slate hearth for my fire place, when the builders plasterd the sides of the fire place they droped plaster on the slate and now it has left white marks how can i remove them,it looks awful. Please help

  7. Ian Taylor | Nov 26, 2010 | Reply

    Hi Jean,

    As long as the slate is a good one that is not acid sensitive, I would try a mild acidic cleaner based on phosphoric acid. Us it diluted as per the instructions. Do not use anything based on hydrochloric or muriatic acid, they are to strong and have dangerous fumes.

    One other thing you could try is a product called Grout Haze Clean Up by Aqua Mix, I have used this neat to remove plaster dust quite effecively.


  8. steve | Dec 19, 2010 | Reply

    I have just had a gas fire installed. Now, after the fire has been used, the slate tiles on the hearth are rusting. Any ideas how I can remove this, and how can I prevent it coming back? Many thanks.

  9. Ian Taylor | Dec 20, 2010 | Reply

    Hi Steve,

    The rusting is a natural phenomena with this type of slate, there are a variety slates on the market, from many different parts of the world, they can be made up of a wide variety minerals. Sometimes there are iron bearing minerals in the stone and when these are buried deep in the rock and not exposed to the air they stay unaffected. However, as the slate is split and processed for sale, fresh faces of the stone are exposed to air and water, (water from cutting, from the installation and grouting process, and even just the ambient moisture in the air). as everyone knows, when Iron mixes with water in the presence of air, it reacts with the oxygen; oxidizes – or put another way – rusts.

    As this is not a stain that has been deposited in the stone, it is not quite so easy to remove. It is part of the stone, however you may have some success with an acidic cleaner, choose one based on phosphoric acid, or if you can get hold of it, Extreme by Aqua Mix, follow the instructions on the bottle. If successful, dry the stone so it is free of moisture and then consider sealing the slate, to help manage the amount of moisture that the slate is exposed to in the future.

  10. Amanda jane | Jan 2, 2011 | Reply

    I have a limestone floor in my conservatory and before we put the floor down we washed it all with relevant cleaners you can buy then once down and grouted we covered whole floor in a selant, however I have knocked a home oil freshner over and it has put a slight yellow tinge to the floor, when it happen I soaked as much as I could with kitchen roll and then washed the floor down with plain water, however this hasn’t cleared it, everytime I mop with plain water it releases the smell of the oil again, any ideas how to rectify?

  11. Ian Taylor | Jan 4, 2011 | Reply

    Hi Amanda,

    OK you are going to need a degreaser for that, hopefully your sealer has done its job and is keeping the oil at the surface. First get q good degreasing cleaner like Heavy Duty Tile & Gorout Cleaner by Aqua Mix or similar (high alkaline), mix in accordance with the on bottle instructions. Then apply to the oil and leave it to sit for about 15 minutes. Then scrub and mop up. Now rinse with cleaner water and mop up. Dry the floor and inspect, it should have remvoed much if not all of the oil. It may be wise to top up the sealer in that part once dry.

    Hope that helps


  12. Gillian Phillips | Jan 9, 2011 | Reply

    Have just installed an unsealed slate floor in my bathroom but before I had chance to seal it someone has missed the pan and it now has some dark urine marks on it. I rinsed the area with warm water, to no great effect.
    How can I get these out, and what sealer is best for a matte finish?

  13. Ian Taylor | Jan 10, 2011 | Reply

    HI Gillian,

    I would try a high alkaline cleaner (such as Heavy Duty Tile and Grout Cleaner). Pre wet the floor, particularly the area around the stain (so as to fill up the tile with water and get underneath the stain). Then mix the cleaner as directed (I would use about 1:4 with Heavy Duty Tile & Grout Cleaner), apply the cleaner to the floor, leave it to sit their for about 15 minutes. Now scrub the area with a nylon scrubbing brush.

    Pick up the dirty water with a mop or sponge, now apply clean fresh water and scrub again lightly, then pick up that water, thus rinsing the floor.

    Allow it to dry thoroughly before inspecting the stain. If it has gone great, if not repeat the process and maybe add a little nanoscrub.

    In terms of a mat (natural look) sealer – I would recommend Sealer’s Choice Gold – it is water based and this will work well on such a porous stone. It will not add any colour, nor any shine or finish. For a darker, enriched colour look (but still no shine) go for something like Enrich n Seal – but make sure this is the look you want (like a very wet slate, but with the surface moisture removed) as there is no going back.

    Hope this helps

  14. Julia | Jan 18, 2011 | Reply

    I have a shower room with black polished slate on the walls and my cleaner has sprayed limescale remover on the walls! (arrgh!) it has left White splats where she sprayed it. Please can you advise me of how to rid of these marks?
    Many thanks,


  15. Ian Taylor | Jan 18, 2011 | Reply

    Hi Julia,

    The white ‘splats’ are more mineral deposits – the result of not rinsing the limescale remover (which I am going to assume was acidic). OK, as long as the limescale remove is not based on HCL (hydrochloric acid) then you could use it again. What has happened is that the acid has dissolved the limescale and then been left to dry and so the liquid has evaporated and the mineral (limescale, and/or other salt from the reaction) has been left behind.

    So: pre-wet the slate, then using your limescale remover spray your cleaner onto the affected area, wait a couple of minutes, scrub with a white nylon pad or scrubbing brush. Now, your cleaner may have got this far, so here is the important bit: rinse all trace of the cleaner away with fresh water, should be easy in a shower.

    Now it is a good idea to take an old towel and rub down the slate. Let it dry and see if that helps.


  16. Emma Evans | Mar 5, 2011 | Reply


    We have just taken delivery of a polished piece of welsh slate (heather blue colour) for our hearth. It seems to have some small, whitish / very light green circular marks on it. We are not sure wether these are part of the make up of the slate or are a type of stain. Would it harm the slate to try to clean them off with anything. As we don’t know what may have caused them we are unsure what to use.

    We have asked the quarry about this but they say it is natural, it just doesn’t look very natural – it looks more like something has been spilt on it.

    Have you any idea what it could be or wether it is indeed part of the slate?

    Many thanks,

  17. Charlotte | Mar 8, 2011 | Reply

    We have just had a slate hearth put in and before we’ve had chance to seal it I have spilt some distilled vinegar onto it. Just a small area about 4cm x 3cm. The slate returns to its dark charcoal colour when wet. I.m guessing that the surface is etched but still feels smooth. What can I do? I’ve seen some advice to use polishing powder but where do you get this from?

  18. Ian Taylor | Mar 9, 2011 | Reply

    Hi Charlotte,

    If it is good quality slate, it should not have etched, but the acid in the vinegar may have taken something out I guess. I am not sure polishing powder is the best way to deal with it, that would mean re-polishing or honing the entire surface most probably and that is really a professionals job as you need the right equipment to do it and it takes practice to get good results. If it returns to the tight colour when wet then perhaps using a colour enhancing sealer (like Aqua Mix Enrich n Seal for example) – provided the stone has not been sealed as you say this could be the answer as it will have the same darkening effect as water but it will be permanent.

    Hope that helps


  19. Ian Taylor | Mar 17, 2011 | Reply

    Hi Emma,

    Actually, I know this slate quite well and have worked with it personally several times. The light green circular marks are, I’m afraid, very commons and 100% naturally occurring – like veins in marble – they are just a part of the stone. The slate is made up of various materials including clay and other minerals, originally laid down as a sedimentary rock, then subjected to low grade metamorphism. The light green spots are concentrations of certain minerals and you will find they go through the stone (a bit like choc-chips in cookie dough) so they are not going to be cleaned off the surface. If you were to cut away or split the surface to a depth that would remove one green spot, you will most likely uncover several more.

    I can understand your disappointment, particularly if you were not made aware of this before purchase – maybe you have an argument from that perspective? As it is a singular piece for a hearth (as opposed to 100’s of m2 for a floor) it is perhaps not unreasonable to ask the quarry to take the time to ‘sort’ through pieces to find one that is more uniform in colour – that would be my opinion, but I do not know if they would do this for you.


  20. Nina | Mar 22, 2011 | Reply

    I had the chamber of my fireplace lime rendered recently, I have small deposits of the plaster on my natural slate hearth and no amount of scrubbing fetches it off, could you advise of anything that I could remove it with. Thanks

  21. Ian Taylor | Mar 23, 2011 | Reply

    Hi Nina,

    I have found Grout Haze Clean Up by Aqua Mix very effective for removing plaster in the past, if you can get some it might be worth a try. Failing that I would try a more direct acid-based cleaner – something like Phosphoric Acid Cleaner/substitute again by Aqua Mix – or other equivalent – but NOT a cleaner based on hydrochloric acid (HCL) such as used in many brick cleaners – it is far too strong and the fumes can damage metal finishes.

    Hope that helps


  22. Rupert | Apr 25, 2011 | Reply


    I have what I am pretty certain are textured slate tiles on my balcony floor. Between the tiles there has, over the years, built up a whitish residue from frequent rinsing with water. The balcony is pretty much protected from the elements. Living in London as I do, with its extra-hard water, I imagine this residue to be limescale – it certainly looks like it.

    The surface of the tiles looks generally ok although there appears to be a slight ‘haziness’ to it and could do with some improvement.

    I am writing to enquire whether you know of the best product to use to treat both issues but predominantly the residue between the tiles.

    I look forward to your reply.

    Many thanks.


  23. Ian Taylor | Apr 27, 2011 | Reply

    Hi Rupert, on the face of it this sounds fairly simple and your ‘diagnosis’ sounds fair (from your information it does sound like hard water deposits building up over time, rather than efflorescence coming up from below). Provided your slate is not acid sensitive (some of the multi-coloured rusty looking ones can be a bit sensitive to acids) then a mild acid cleaner, dilute with water should do the trick in one application.

    First you need to make sure you get the right acid-based cleaner – DO NOT buy a brick cleaner, or a cleaner from a builder’s merchant that is based on hydrochloric acid (HCL)- it is far too strong and the fumes alone can damage metal finishes. So for example you could buy a Phosphoric Acid based Cleaner
    Do A Test First!

    Mix some of the Phos Acid Cleaner say 1:5 with water (that is 5 parts water), apply it to a small test areas on both the slate and the joint. You may see a small amount of effervescence (fizzing or bubbles being generated) this is just the acid reacting with small amounts of cement in the grout joint (it is actually etching the grout at a very low level, no real damage will result unless the grout is weak or poorly installed – but it might lighten the colour slightly- this is unavoidable).

    Leave it for a couple of minutes the scrub lightly with a scrub pad, rinse with fresh water and let dry. The rinsing stage is crucial, as the mild, dilute acid will quickly dissolve the lime-scale but it will also dissolve a tiny amount of cement from the grout, in the process a by product, a salt from the reaction of the acid and the alkaline cement, will be produced. So the liquid solution will have slats and diloved lime-scale in it, if you just allow it to dry you get that residue re forming on the surface and the floor could look even more white and patchy than before – so: apply; dwell; agitate; remove; RINSE and then for good measure, dry – use an old towel or something to pick up the rinsing water. This takes both the remaining water and any traces of residual acid/limescale/salts etc.

    Let it dry thoroughly; check for damage to the slate (doubtful) check to see if it has cleaned all the limescale away – for example one application may easily remove the fine haze from the slate, but it might take two applications to get it all from the joints.

    You can always vary the dilution; if you found that one application cleans it up 100% really easily, then try a 1:10 mix (the less acid you use the better, and you make the product go further also). If it struggles make it a bit stringer, say 1:3. IT is better to do 2 weak applications than one really strong one.

    If your test is successful, then repeat the above process on the rest of the floor.

    Hope that helps


  24. Rupert | Apr 27, 2011 | Reply


    Thank you so much for your time and attention.

    I shall follow your helpful instructions/advice precisely.



  25. Paula | May 1, 2011 | Reply

    Hi Ian, We brought our house 8years ago and the fire place has a black slate surround, it is looking dull now. I am unsure how to bring it back to life. I have been cleaning it with just soapy water and drying it off.

    Please could you give me advice.

    Thank you

    Paula :0)

  26. Ian Taylor | May 3, 2011 | Reply

    Hi Paula,

    The type of black slate typically used for this is dense and can be honed to quite a smooth finish, not a high shine, but what we call a fine hone: flat, smooth and with a satin sheen rather than a gloss. on a floor this can of course wear and dull down through mechanical means, however on a hearth, and certainly a vertical surround, it is not subjected to this kind of wear (unless you are particularly vigorous in your cleaning) -so the dullness is more likely to be a build up of ‘something’ on the surface. This can often be residues from cleaners.

    The first thing Would try is a high alkaline cleaner (like Heavy Duty Tile and Grout Cleaner) maybe with a bit of a cream abrasive like nanoscrub added. Apply it dilute as per instructions, keep applying it with a sponge for 5 minutes or more (to keep the vertical surface wet) then use a white nylon polishing/scrubbing pad and lightly scrub the area. Rinse it down with clean water and rub dry with a clean towel.

    Try this first as it may remove a semi invisible ‘scum’ that could have built up over the years. If this does not restore the stone, then come back to me.

    Hope that helps


  27. Rob | May 12, 2011 | Reply

    Hello Ian

    I’ve read through all your great advice on this page but still have a question I hope you help with?

    I tiled the inside of the shower enclosure using random (Indian I believe) slate or different colours textures and density it seems. I was very meticulous with the tiling, and machine cut each tile, set them in a deep bed of cement (they are random thickness and riven) and achieved and excellent 3mm grout line throughout. I actually masked lines of tiles when grouting to avoid mess. Finally I sealed the tiles with 3 coats of Fila slate impregnator upon completion.

    One thing I neglected to consider is that I live in a hard water area of the UK (South Coast – so water is filtered up through chalk boreholes).

    After a couple of years the shower is not looking as hot as it did, and the main problem appears to be limescale clinging to the rough surfaces of the tiles. This gives the appearance of a dry salty coating when dry, but disappears once the tiles become wet.

    I would like to remove this film, but am very wary of cleaners after making the mistake of cleaning the chrome shower control with LimeLite. I obviously didn’t do this with much care or rinse it correctly, as it left some light staing to the tiles and grout immediately below the faucet/control.

    I appreciate it may be harder to advise me because of the composition of the random slates I’ve used, but if you can offer any advice it would be much appreciated.

    The really affected areas are on the wall directly below the showerhead, the rest and high up aren’t so bad.

    Kind Regards


  28. Ian Taylor | May 13, 2011 | Reply

    Hi Rob,

    I just tried to find out what the chemical composition of Limelite is – and there is no SDS on their web site. It does state not to use the product on marble or limestone – so, given that and that it is designed to remove limescale, we can safely assume it is an acid-based cleaner of some kind. My question though is what acid? If it damaged your chrome, then it is strong, and quite possibly something like HCL (hydrochloric).

    HCL can cause all kinds of damage, in fact the fumes from such a product alone can dull metals. But since we do not know what they use in that product, we should not speculate.

    What I can say is that a cleaner based on a weaker acid such as phosphoric will usually present no such problems. Products like Aqua Mix Phosphoric Acid Cleaner (there are a lot of similar products out there) contain about 22% phos acid, and they are normally diluted further for use. Such products are usually perfectly safe.

    In your case, you may well have to resort to such a product as a build up of calcium film (for that is what the limescale is) will really only be broken down chemically by an acidic cleaner. You could try an off the shelf cleaner based on lemon juice but that is citric acid and believe it or not that can be quite potent.

    you could try a mild abrasive, like nanoscrub – this is completely non destructive and works purely through mild abrasion however my guess is that after 12 months of build up, you will probably need an acid clean first, thereafter, a product like nanoscrub will be ideal for say monthly maintenance, helping to prevent future build ups.

    So, test a safe, phosphoric acid cleaner in a small area, read the on bottle instructions and try a very dilute solution first. my procedure for this would be:

    1. dilute the phos acid cleaner say 1:5 with clean water
    2. pre-wet the slate
    3. apply the dilute solution to the slate with a sponge, brush or even a small spray bottle, leave it for a few minutes – 5 should be plenty. Keep it wet in that time, with more solution if needed (esp if on a wall)
    4. now using a soft scrub pad or brush, lightly scrub the area
    5. rinse with clean water
    6. dry with a towel

    when thoroughly dry inspect the area, if no or little improvement make a stronger solution of the PAC, say 1:3 or 1:2 (you can use it neat but there is no need to use more than you need to get the job done).

    Only word of caution is that the acid may affect both your slate and the grout, to a minor degree: The cleaner works by reacting the acid with the very alkaline calcium, but it will also react with the calcium in the cement of the grout, however it is only going to be very weak and the acid is very quickly exhausted or ‘spent’ (one of the reasons why there is little point waiting more than 5 minutes for it to work). In reality this means it will do little more than chemically scrape the surface of the grout (cleaning it up too – it is a bit like using T-cut on a car’s paintwork), also, before it can react with any cement, it will have to get through the calcium deposits that are no doubt on the surface of the grout also. So the worst you should expect is a slightly brighter, cleaner grout joint.

    Also, if the slate is a multi-coloured Indian type, and some of those colours are rusty brown, then they may be affected slightly too. They are rusty brown for a reason – it is actually rust – well kind of anyway, there are all kinds of minerals present in the clay/shale that the slate used to be, including iron. Having been split into the ‘slates’ and exposed to the to the atmosphere (oxygen and moisture) the little bits of iron oxidize and create the rust. Well, phosphoric acid loves rust and will react with/dissolve that too.

    Again, the effect will be minimal, the acid will quickly ‘tire’ and there will be more ‘rust’ than it can remove but it may lighten it a touch.

    Finally, make sure to keep the acid cleaner away from any other acid sensitive surface – you won’t have any problems with fumes and it is nowhere nears as dangerous as an HCL based product, but anything that is sensitive to acids will react – so keep away from polished marble for example. Chrome and other metals should be OK – but always best to be cautious – hope this helps


  29. Paula | May 21, 2011 | Reply

    Hi Ian
    Great website by the way. I have a black slate fireplace at home and we accidently spilled a glass of champagne in it a few weeks ago.

    It wasn’t cleaned up immediately and now leaves a white stain (I am guessing the acid from the wine has caused this)

    Could you give me any advice on what products are available on the market which may attempt to remove this.

    Thanks in advance for your help.


  30. Ian Taylor | Jun 1, 2011 | Reply

    Hi Paula,

    Sorry about the delay in responding – I am getting so many comments now it is becoming a full time job answering them. I am not sure the problem here is acid as many black slates are pretty insensitive to acids.

    If it is as a result of the acidic champagne, then it is not so much a stain, but an etch. An etch simply means that some of the stone (or the finer particles from the surface) have been affected, or to put it bluntly, dissolved, by the acid. It is a kind of chemical burning an unlike a stain which is a deposit of something left behind ON the stone, an etch is parts of the stone having been physically removed or at least altered – so there is nothing t ‘get off’.

    If, it is an etch (typically it will look dull, feel less smooth to the touch and will be greyed-out in terms of colour, all compared to the rest of the stone) then the only real way to fix it, properly that is, is to refinish the surface. This means mechanical griding/honing/polishing with abrasives, most likely diamonds pads. This is usually done by professionals mainly due to the cost of buying the diamond tools required. IF the hearth is movable, you may be able to take it to a stone company (such as a granite worktop fabricator, or a gravestone/monumental mason’s establishment as they could bench finish the slate again for you) otherwise you may need a stone restoration professional to come to you in order to do it on site.

    One ‘cheat’ ( and I say that with tongue in cheek) that can sometimes help is to colour the etch with a good colour enhancing sealer – this can be effective if the slate is sealed with the same sealer in the first place, or it is as yet unsealed and you treat the whole thing. I describe it (perhaps unkindly) as a cheat simply because it masks the problem, rather than fixes it – but it is a perfectly valid solution – it is also easy to do and you could do it yourself. You would first need to clean the slate and let it dry thoroughly.

    If, on the other hand it is not an etch, but simply dried residue from the champagne that has got into the slate’s micro-texture – then try cleaning with a mixture of a high alkaline cleaner and a cream abrasive such as nanoscrub- I should have put this sentence first in hindsight!

    Hope this helps, please come back to me if you need further assistance.


  31. Ian Cannon | Jun 18, 2011 | Reply

    At present I am having a slate floor in the front porch of my home.It is semi open to the eklements. It is approx 8ft X 3ft. It has been laid and there are iron rust deposits quite visible on two of the slates. The builder says that they can be cleaned. As this is rust::

    Can it be cleaned

    Will it rust further and show more.

    Should I insist that he remove them and replace.

  32. Chris | Jun 20, 2011 | Reply

    Hi Ian
    Very pleased I found this site – I’ve been searching the Internet for an hour!. Hope you may be able to offer some advice to a novice – we have purchased a house with slate flooring in the kitchen and the grout definitely needs cleaning. I purchased some HG grout cleaner that contains NTA (nitrilotriacetic acid) – will this damage the slate? I see you recommend phosphoric and staying away from HCL, but any thoughts on NTA?
    I also have some Plasplugs tile sealer – would this help, and should I use this before or after the grout cleaner?
    Thanks in advance,

  33. Ian Taylor | Jun 21, 2011 | Reply

    Hi Ian,

    Some slate can contain iron bearing minerals as a naturally occurring component in their matrix. When the slate is split (to make the tiles) and thus a fresh face is exposed to the elements and cleaning water etc, the iron can oxidise – and so form rust. If this is the case then yes it can be cleaned to some extent, usually with the help of a MILD phosphoric acid based cleaner. But it may only remove the surface oxidisation, and not the rust from within the surface, or the source of the iron, so it will oxidise again. This is natural and on large areas it would be impractical to remove every affected stone, but if it is just two tiles in a small porch, I personally do not think it unreasonable to have them swapped out (the replacements could be the same though, of course).

    If it is a rust deposit that has come from outside of the slate (something rusty left on it, or rusty straps on the crate in which the slate arrived into the UK for example) then you may well be able to clean it off and not have it re occur.

    Hope this helps

  34. Ian Taylor | Jun 21, 2011 | Reply

    Hi Chris,

    From what I can tell (and I am no chemist) that is used as a chelating agent – like a water softener – so not an aggressive acid – it is probably in there to help ‘grab hold’ of calcium and some other mineral deposits – I would love a chemist to come on and give us a better explanation

    In any case I think it is perfectly safe to use, but I think for general deep cleaning of existing grout, a high alkaline degreaser would be more efficient.

    Regarding the sealer, you don’t say which one it is, I think they have a coating sealer – leaves a satin-type finish, or an impregnator – soaks in and gives below the surface protection, but no actual surface protection and no sheen. So a lot depends on how you want it to look. Also, I understand that that company is no longer in existence, so you might want to test the product on some spare slate, as you cannot be sure how old it is, and if you run out, you may not be able to get any more. Their business was taken over by another company and sold through a very big ‘shed’ but I do not know for certain if the formulations are the same.

    Hope this helps


  35. Abdul kadir | Jun 23, 2011 | Reply

    Hi Sir
    I my self Abdul
    Kadir working in KSA in KING Abdula university Of science & Technoligy with Saudi Oger LTD company as a Group leader In Housekeeping Department

    There in the university they had use an egyption stone on flore & it it is very difficult to remove the stain when the stone absorve the stain

    Sir please give some advice for removing the stain

    Thanks & best regard

  36. Rob | Jun 23, 2011 | Reply

    Hello again Ian

    Just to follow up on the kind advice you gave me with regard to removing limescale from the slate tiles in my shower enclosure, I’d just like to say that it was a complete success.

    I kept it as simple as possible using your advice as a guide, so…

    1. Strip off, have a shower to get the tiles good and wet.

    2. To a wet soft’ish nylon scoring pad I applied a small amount of Limelite and gently scrubbed the tiles in vertical and horizontal movements.

    3. Leave for about three minutes

    4. Shower again, rinsing all the walls off.

    5. When dried the tiles were almost scale free, although the grouting has suffered slightly and turned white’ish in places.

    Many many thanks for your advice


  37. Lynette Zito | Jun 24, 2011 | Reply

    Hello Ian
    I have woodburning heater with a slate hearth. My sister, a zealous cleaner, was attempting to clean the glass door on the heater and split methalyted spirits on the slate. I now have a whitish splash mark on the slate at the front of the hearth. Would really appreciate your advice.

  38. Ian Taylor | Jun 24, 2011 | Reply

    Hi Abdul,

    The Egyptian Limestone is very nice, but as you say it is also very absorbent, especially if it is not sealed. But, even if it is sealed with an impregnating sealer it is so porous that you can still get surface staining.

    You do not say what the stains are (coffee, food, general dirt etc), but the first thing I would try is a high alkaline deep cleaner, allow it to dwell on the surface for a while, then scrub lightly with a white hand pad, or a white pad on a rotary machine. Use a Wet Vac to pick up the water, then rinse with fresh clean water, then dry the floor with towels.

    I would also try adding some cream abrasive (check it is designed not to scratch the limestone).

    For isolated spot stains, try using a poultice ( you can buy poultice powders to mix with water of alkaline cleaners, or ready made poultice pastes) Apply the poultice to the stain, cover with plastic and leave for 24 to 48 hours, remove and rinse.

    Hope this helps


  39. Ian Taylor | Jun 24, 2011 | Reply

    Excellent!- thanks for letting us know


  40. Ian Taylor | Jun 24, 2011 | Reply

    Hi Lynnette,

    Interesting one this. Usually a solvent like Meths would not leave a white mark on the slate, (often Meths is coloured violet and so the pigment/dye and even the oiliness of the meths itself can make its presence felt in light coloured materials).

    So, a couple of things come to mind: 1, if the slate was what I would call a low grade slate (nothing wrong with that), by which I mean a relatively young (geologically speaking) stone, they are sometimes not as dense, more colourful, more porous than older slates (like Welsh slate, or the green Vermont Slate for example) then I have seen some, where the minerals that make up the colours in the stone are not shall we say, ‘fixed’ in other words they can be washed out (we see this when using acidic cleaners on rusty coloured slate, the acid removes some of the iron and thus reduces the colour intensity). I have not seen a solvent do this but I would guess it is at least conceivable that some mobile pigment could have been removed. If this is the case, and I have to say I am very doubtful, then there may not be a whole lot you can do about it, unless you can get an enhancing sealer into the stone. This may not be possible if the slate has already been sealed. I guess the worst case scenario would be getting the slate re-surfaced by a pro.

    2, I am not sure if your hearth has been sealed, either by yourself or the supplier, if it has then a much more plausible explanation could be that the meths has simply stripped, or partially stripped some of the sealer. Often coating sealers will take several attempts to break them down using solvent based strippers, the first attempt simply removes the top layer, leaving them damaged, and often, turn a kind of ‘dried on milk’ colour. If you think this could be the case, try dabbing a bit more solvent (preferably a stripper designed for removing sealants from stone). See if you remove the white stains. If so you may find you have to do the whole hearth, then reseal.

    One more thought just occurred to me, what was your sister cleaning? If she was cleaning something above then the meths would be presumably, breaking down some contaminant on some higher surface, so what actually dropped down onto the heart was meths, along with whatever was now dissolved in the meths – a soluble contaminant. The meths then evaporated leaving behind whatever it was carrying. Again, dab a bit more meths on a cloth (or better still a stone stripper) and rub the white patch – you are not going to make the situation worse, as if it does not work, then it is possibly one of the above scenario’s anyway.

    Hope this helps


  41. Suzanne Elliott | Jul 24, 2011 | Reply

    Hi Ian,
    I have a slate floor in my bathroom that has been sealed. I have just spilt a bottle of nail varnish remover on it and it has now come up as a massive White stain. I wiped it up straight away but the White will not go away. I’ve tried using tile stripper to remove it but when dry, the stain comes bk. I am gutted. What can I do?

  42. Ian Taylor | Jul 25, 2011 | Reply

    Hi Suzanne,

    My quick appraisal of this is that the acetone in the nail varnish remover, has partially stripped the sealer ( I am assuming it is a coating sealer). We often see this on thick coatings, a stripper (usually a solvent, and Acetone makes a good stripper) can sometimes need two or three applications to completely remove a sealer. The first application kills the shine and effectively damages the coating, by taking a thin layer of it away – in doing so it makes the rest opaque/white etc (it is a bit like when you peel old tape of a surface and instead of coming away cleanly, it delaminates and leaves part of itself on the surface)

    So, repeating the process shoold remove the rest of the sealer – just as a test, try some more nail varnish remover on the white marks, leave for a few seconds then rub with a cloth/scrub pad. If it works, or appears to reduce the mark then you are on the roght track. It may be that the stripper you tried is not as strong as the acetone or you may have not left it on for long enough – persevere with several applications. I would suggest doing this up to the edges of the tiles affected. When removed, rinse with water and allow to dry completely. They re-seal.

    The point is I do nothink yo have damage the slate in any way, you have damaged the sealer alone, in my opinion.

    Hope this helps


  43. Kevin | Aug 13, 2011 | Reply

    I recently black slate floors installed in my bathroom. Marble was aslo being laid in the bathroom at the time around the shower and tub. When I was first able to see the floors there were blue spots that looked like stains – the spots/stain were in an oval shape and not the pattern of the stone. The builder told me the spots were in the stone, however when I selected and ordered the stone from the stone company we were shown 4 slate tiles and told the color variation would only be between the 4 tiles. None of the variations included any blue spots. Were the spots part of the original stone? Can the spots be removed?

  44. Ian Taylor | Aug 16, 2011 | Reply

    Hi Kevin,

    From your description (and I do not know if you are UK based or not, nor do you tell me which slate you have) I would say it is actually quite likely that this is in the stone. For example, with Welsh slate (renowned as among the best slate in the world) these blue/green oval markings are quite commonplace and are a naturally occuring due to minerals in the stone.

    If you have these, and I suspect that you have, then no, there is no way of removing or masking them, you will find that if you were to cut through through the sotne, the marks would extend all the way through the stone. They are perfectly natural and not technically ‘faults’.

    On the issue of what you ‘thought’ you were getting, I can sympathise, maybe you have a case that if these blos are naturally occuring, the vendor should perhaps have shown you a more rerpresentitive sample in my opinion – but that is one for legal advice

    hope this helps


  45. Graham | Aug 26, 2011 | Reply

    Dear Ian, We have just laid a blue/black slate patio (chinese/Indian slate bought from Ruscrete). Unfortunately, we had to lay the slate before the external patio walls could be rendered. We’ve just experienced a lot of wet weather and although plastic sheeting was laid down to protect the slate, the sand/cement mixture has washed over the slate and appears to have stained it white. Its a riven slate. I should also state that the slate has not been treated with any coatings etc. Any advice much appreciated. Best wishes. Graham

  46. Ian Taylor | Aug 30, 2011 | Reply

    Hi Graham,

    There is probably, really only one way to solve this and that is an acid clean, Suggest you use a proprietary (mild) acid based cleaner, one based on a safe acid like Phosphoric or or one of it’s alternatives. Unless the render splashes are really thick, avoid using a brick cleaning acid based on HCL if you can. If you have to use one, take care and keep it away from anything metal like furniture and frames etc.

    Generally the milder and weaker [the acid cleaner] the better [for the floor and grout joints] – even if it takes more cleans/ several attempts. Some indian type slates are multicoloured due to exposed (and therefore oxidized) minerals like iron (hence the rusty colour). Giving them a good scrub with even a mild phos acid cleaner can diminish some of the colour (because it cleans rust away as well as cement) but in time as the slate is left to oxidize, some of this will come back.

    Given the slate is not sealed , it will be very porous so pre-wet the floor – a lot, (this is important) before putting the cleaner on otherwise it will dive into the stone and you will just waste time and product. Apply the dilute cleaner (read instructions and gove for weakest strenght first, make it stronger if needed) typically try a 5:1 mix (1 part acid cleaner to 5 parts water) and see how you get on. The more acid you use ( and you could use it neat, as most acid based cleaners like this are already only circa 25% acid the rest is water and detergents etc) the faster it may work, but the more likely it is to kill some of the colour of the slate, and have a ‘bleaching’ or whitinening effect on the grout joints.

    Let the acid cleaner sit for just a few minutes then start scrubbing. For large areas out side I would recommend hiring a rotary scrubbing machine with a hard to medium brush head. Scrub, then using a hose/pressure washer and squeegee, rinse the cleaning solution away – DO NOT JUST LET IT DRY.

    Then repeat if needed – you may have to do this several times – better to take small layers several times than go in too strong and dmage the slate/grout etc.
    Finally rinse again with water. Some whitening of the grout may result but this will weather and dull down again quite quickly. Watch out for efflorescence – white mineral crystals forming in the joints due to all the water that you are going to need ot use. If you do get this, you can treat the floor with an efflorescence cleaner and inhibitor called Eff Ex – act as soon as you see it, otherwise you would need acid again and that could just kick off more efflorescence – it can become a viscious circle.

    You can ge the products you need, including the Eff Ex at All for stone (see link ad) they may not have them all listed so give them a call.

    Hope this helps


  47. Nick | Sep 15, 2011 | Reply

    Dear Ian – i have just laid some honed Brazilian slate in a shower room. I wasn’t too sure whether it needed sealing but I have done it anyway. On the first attempt I left it too long and it left a residue (i.e. you could see shoemarks). I took the sealant off with Lithofin remover and sealed again with lithofin stain-stop, this time just covering each tile and wiping off almost immediately. The effect is better but I still get faint boot sole impressions on the tiles. Can I do anything about this?

    Many thanks

  48. jo | Sep 15, 2011 | Reply

    hye we have had black slate layed in kitchen they havent been treated yet we nd to get the white marks out of the slate first we have usd grout residue remover but you can stil see the white any ideas on how to get rid of the white marks?

  49. tom mcculloch | Sep 20, 2011 | Reply

    we have a one year old slate hearth which was sealed by the supplier with WD40. During the recent storms rainwater came down our chimney liner and settled on the slate hearth for a couple of days. We have been left with stains on the hearth and white marks where some of the rainwater has dropped on to the front of the hearth in our attemptg to clean. we checked with the installers who told us to wash with warm water and detergent and use a nail brush to scrub but it is making no difference,
    can you help

  50. Ian Taylor | Sep 20, 2011 | Reply

    Hi Nick,

    It could be that the slate is very dense, and not in need of much sealer, and so this makes getting the sealer in difficult, or at least what can happen is that the slate takes in very small amonts of sealer (all that it needs) and leaves a film on the surface. Then, you, think that yo have taken 100% of the surplus off but, more often than not there are traces left that you cannot really see. ( it takes a bit o practice and lots of changes of cloths etc to remove all the residue effectively – most people, even in the trade will always leave somnthing behind. If this is the case then the residue could be holding small particles of sweat/skin oils etc to leave the ‘footprint’

    You could try using a mild detergent or even a mildly abrasive cleaner like Nanoscrub or Microscrub (contact all for stone by phone for details, see advert on the top right) .

    Also, it could be that the slate surface, whilst appearing perfectly flat and smooth, is actually micro-textured – has tiny pores and surface texture that is too small to see, but big enough to grapb tiny particles and hang on to them – in this case they are not stains, but just trapped dirt and a good stiff brush (again with some Microscrub) could be the answer.

    Hope this helps


  51. Ian Taylor | Sep 20, 2011 | Reply


    I am assuming that the white marks are grout residue. If so then you may need to use the grout residue remover several times – as it will be a mild acid (and don’t be tempted to use a strong acid/brick acid or any other hydrochloric acid based cleaner). Such mild acid cleaners are designed to do the cleaning with minimal damage to the grout in the joints (which is exactly the same material as that which you are trying to break down on the slate) – so it is often necessary to repeat the clean several times, each time taking a bit more away. Also you may need to use a scrubbing brush.

    Hope this helps


  52. Ian Taylor | Sep 20, 2011 | Reply

    Hi Thomas,

    Well first of all WD40 is a great product – but not for sealing slate! – I can see the thinking, an oil thinned with solvents, a bit like a sealer, except the oil is designed to be a lubricant (yes also a water repellent) but it does not form a polymer film – an inner skin to keep stains out. Also, I do not imagine it lasting too long either – it will remain mobile (not ‘set’ or cured like a sealer) so it will be removed with normal cleaning over time, it will even gradually just degrade on its own – so all in all – not an effective sealer (bit of a trade ‘cheat’ in my opinion).

    OK, the white marks could be due to some impurity in the water, if your chimney is limestone, for example, water could have picked up some soluble lime (and depostited it on the slate as the water evaporates) or if you live in a hard water area you could have a high calcium content (don’t think Glasgow does mind you) again you get calcium deposits left behind. Or it could be residue from detergent.

    It could also be that the WD40 oil slightly darkened your slate and the sitting water has washed more out of it in those areas. Do the white areas disapear (albeit temporarily) when the slate is wet? – if so try a little acidic liquid – like a clear vinegar – just to see if there is anything mineral (the acid will disolve it), rinse and dry and look at it again. if it has lessened the problem, get a mild acid based cleaner and try that.

    Conversley the white marks could be caused by acid etching – acid rain being the culprit or (and I am no chemist) I beleive it may be possible that some forms of soot, (depending on several things) can have a low ph (acidic) although often they are alkaline – so rain water picking up soot, can become acidic which could on some slates cause a slight etching. The reverse could be true also, if the water + soot resulted in an alkaine solution – that would have the effect of stripping out the WD40 – or what remained of it.

    If acid etching then masking the etch marks may be an option, if all else fails, try adding a bit more WD 40 – as it was used before, it may top up the oil and make the look more uniform – not ideal, (this is where I would normally recommend an enhancing sealer but it is too risky now, the sealer mey not penetrate correctly due to he presence of the remains of the WD40) but it may mask the marks.

    Hope this helps


  53. Nick | Sep 26, 2011 | Reply

    Hi Ian – many thanks for your reply…it’s very helpful. I’ll try a mild detergent and hope that works. I’ve noticed that the residue seems to be gradually improving now (after about 10 days!)…so am hoping that, with a bit of detergent, the problem might go away.

    Thanks again,

  54. Charlie | Sep 30, 2011 | Reply

    Hi, in trying to be helpful my teenager washed the kitchen slate floor with a product callede Cillit Bang leaving bloches and stains all over a wide area, is there anything I can do to renew the appearance thank you

  55. Ian Taylor | Oct 4, 2011 | Reply

    Hi Charlie,

    I have heard so many storeis about this product, itis not that it is a bad product, just that it contains acid and should not be used on acid sensitive surfaces (like many stone and grouts).

    So, what could have happened? Well, if the slate is a coloured vairiety, with the colours coming from minerals such as iron etc, then an acid can dull and etch them, taking with it some of the colour intensit which could leave the slate looking drab. If you have white patches then there is another possibility, that there was a feint, barely noticeable grout haze or other film on the surface and the acid has etched this rather than the slate. Or, perhaps the slate is fine and the acid has brought disolved grout grout out of the joints and left it on the stone.

    Try using a good deep cleaner (alkaline) and a scrubbing pad to see if you can loosen anything from the surface. If the actual slat eis damaged itslef, then what happens when it is wet? – does the colour come back, at least until it dries out?. It may be possible to use an enhancing sealer on this – provided the slate is not already sealed.

    One other thought that ocurs to me, and forgive me, but not eveyone will correctly identify the stone, are you 100% certain the stone is a slate? – it is just that not all slate is sensitive to acids where other stones, like likemsstone for example typically are very sensitive.

    If you could sned some pictures I might be able to help more

    Hope this helps


  56. peter | Oct 6, 2011 | Reply

    ih ian iv just bort some second hand slates to do my garage roof but when iv looked at them thev got bitumem tar like substance thaks if you can help me to find out how to clean them

  57. taffy | Oct 6, 2011 | Reply

    Picked up our Italian honed slate hearth today.
    Would appreciate any advise regarding cleaning, and sealing the stone.
    Didnt get any advise from the store due to collecting from pickup point at the rear of the building.

  58. Ian Taylor | Oct 12, 2011 | Reply

    Hi Peter,

    To be honest the only way to chemically remove tar is a strong solvent. First scrape as much of the solid tar off as you can then use a solvent, you could try white spirit or turps etc. to get the residues. It may take several attempts.

    Hope this helps


  59. Ian Taylor | Oct 12, 2011 | Reply

    Hi Taffy/Ceri?

    I do not know precisely what slate you have but if it is honed then it is smooth so an imprgnating sealer is the way to go. You may or may not want to consider an enhancing sealer – if the slate is at the moment unsealed – (and you may want to check that the factory/supplier has not put anything on it) does it darken a lot when wet? – if so do you prefer it in this darkened state, or natural? If you prefer the darkened state you could use a good enhancing sealer like Enrich n Seal or Enhance n Seal – make sure you want this though as it is not reversible.

    If you want the natrual look – just a good quality impregating sealer, if the slate is really dense, you may find a solvent based one easier than a water based, if it is qyite porous (slate varies a lot) then the reverse might be true.

    For cleaning, a neutral ph cleaner for routine cleaning, something a little higher in alkalie for heavy, periodic cleaning. If it is just the manufacturing dust/sludge, then some washing up liquid and water might be all you need.

    Hope this helps


  60. Ana | Oct 15, 2011 | Reply

    Hi Ian,
    i have two slate showers the floors are white with limescale. what do i use to remove limescale. the grey slate looks as though it is starting to flake,the cleaner i used was too acidic.

  61. Ian Taylor | Oct 17, 2011 | Reply

    Hi Ana,

    OK, to be honest, if it is a lime-scale issue, and you have a slate that is not sensitive to acids (nor anything within splash-contact proximity) then an acid was the right thing to use – as long as it was a safe one (i.e. not brick cleaner, hydrochloric etc.).

    The acidic cleaner should not be making the slate ‘flake’ – Flaky slates are flaky on their own, and sooner or later they will start to loose any lose flake’s but usually this settles down quite quickly, unless they are really bad. (I have a geologist friend who would argue that some stone, sold as slate is not technically slate at all, but a shale or some other sedimentary rock that has not quite made the full metamorphic change into slate, so it is a much younger rock – the less dense, often more colourful, dusty and flaky slates that we see may fall into this category – nothing wrong with them per se, but they can be more susceptible to flaking).

    I would remove any loose flakes, check the rest of the slate is sound then clean the limescale. Use a safe acid (look on the back if they are tile grout haze removers and they contain a percentage of phospohric acid or one of its replacements, it should be fine).

    Pre wet the floor, apply the acidic solution (may not have to be neat – remember the stronger the solution, the faster it will work BUT, the more potential damage it can do to the grout joint, so start with say a 5:1 dilution rate). Let it sit for a couple of minutes then scrub with a pad or brush.

    Rinse well with clean water, (still scrub a little) to remove the acidic cleaner and any dissolved lime-scale. Dry the slate with a towel/paper towels.

    Bear in mind that the lime scale has come from your water, so drying the slate (i.e. removing the water) before it has a chance to dry and leave a deposit of more lime, is a great way to help prevent future build up. Let it air dry and have a look. If necessary repeat. The other thing to watch for is the acidic cleaner etching your grout, if your grout is pigmented, or dark, it may now be significantly lighter in shade (maybe already as you have already used an acid). Acids can bring tiny amounts of dissolved cement out of the grout, the calcium from the grout, reacts with the acid to create calcium phosphate which is a salt – and can look itself like a white, lime-scale deposit – so it in theory it is possible for the actual treatment to remove the lime-scale and replace it (at least partially) with another similar problem (again it is broken down by more acid cleaner) – so clearly rinsing and drying help prevent this.

    Once you have got the lime-scale removed, and any flaky bits sorted out, let it dry and you will probably need to re seal (especially if some flakes have come of).

    From this point on, make a point of drying the floor, not on every occasion perhaps, but frequently. And then use a milder perhaps citrus based cleaner periodically to keep the lime-scale at bay- again, rinse and dry each time you do this. Also a cream abrasive like Microscrub is a non-acidic alternative for keeping it under control (once the initial build up is addressed) Hope this helps


  62. Ana | Oct 17, 2011 | Reply

    Hello Ian, thanks for the advice, i will try this and seal the tiles. then do regular maintenance.


  63. lauren | Oct 17, 2011 | Reply

    Hi Ian.
    I have had 120msq of slate laid throughout my house. Days after it was laid builders marked large areas with plaster and paint which I am finding it difficult to remove. The floor is disappointingly stained and builders have scrubbed certain areas which has made the floor lighter and dull. It is a natural riven slate and also seems to have grout trapped in the groves on some tiles. Obviously it cost a lot of money to buy and lay and I want to know how I can get the colour of the slate looking consistent throughout the house.
    Many thanks,

  64. Ian Taylor | Oct 24, 2011 | Reply

    Hi Lauren,

    The dull areas that the buliders have scrubbed are dull, hopefully because they have only partially cleaned, and have not rinsed well. This means they may have left residues that have now dried on the surface again.

    In most cases like this, with a good quality slate it is usual to use some form of proprietory acid-based cleaner. Provided your slate is not acid sensitive, and you have not got a highly pigmented grout, this may be the best thing to try. Try to find a product that is based on phosphoric acid or similar, DO NOT use a brick acid or one based on hydrochloric/muriatic acid as this can do more harm than good.

    The phos acid based cleaners are mild and weak, they are already diluted and can be diluted further, they are designed to take small films off the surface whilst doing minimal damage to the surface of the grout itself.

    Test the cleaner neat on your slate in an inconspicuous place just to make sure it does not damage the slate. Then do the following:

    1. Pre wet the floor with a mop or sponge
    2. Mix your cleaner as per instructions – typical dilution maybe 1:5 0r 1:3, apply it to the floor
    3. Leave it to dwell for about 3 minutes
    4.Scrub with a scrubbing brush or wite pad, you may nees a plastic scraper to get into some of the deeper parts of the texture
    5. Pick up the solution with a mop or wet vac
    6. Important step: rinse the floor with fresh clean water, mop up
    dry the floor with moving air and/or towels

    inspect and repeat if neccesary – it may take several goes as you are taking very thin films each time. The trapped grout in the riven texture may need some local neat application of the above.

    Hope this helps


  65. Darlene | Nov 2, 2011 | Reply

    Hi there Mr. Slate genius!

    Excellent advice I see here and so well put so I’m really hoping you’ll be able to help me

    I have my front garden tiled in riven dark grey slate tiles (30cm x 30cm)

    Having saved for an age to get new double glazed sash windows put back in the house we also decided to get the front completely cleaned
    ie. All the brickwork cleaned and re-pointed.

    They tried their best to keep the run-off off the tiles but needless to say the acid used to clean the bricks has bleached the tiles in a lot of places :0(

    It’s etched some areas but some, where gaffer tape, was stuck down is fine so the tiles have a 6cm wide line through them in places!

    So, basically I have white spotted and patchy tiles on about a quarter of all the tiles.

    I had previously sealed with HG Impregnating Sealer but acid being acid it made no difference

    Before I start to weep and sand my little fingers to the boney bone could you possibly offer some advice?

    Many thanks,

  66. Ian Taylor | Nov 4, 2011 | Reply

    Hi Darlene,

    You may be ok here. First of all, dark riven grey tiles, that you had to save for suggests good quality slate (Welsh, Cornish, Brazilian etc) which to my knowledge is not generally all that acid sensitive. You could have a more shale-like Indian/Chinese type product I suppose and some of them can be more susceptible to etching due to their make up.

    However I think a more likely scenario is this: When an acid attacks cement in grout/mortar it kills some of the colour (giving the bleached etched effect) I think you have a residue of the run off that has been left to dry on the surface. Builders and conctractors seem to delight in using acids, that are often to strong (hydrochloric), frequently not diluted to the recommended rates, blasting the problem with their massive acid overkill, then failing to rinse the away the aftermath. I suspect that if you take some more acid (and I mean suitable one, not a brick cleaner so a cement residue remover based on phosphoric acid) dilute it, pre wet the floor, then apply your solution, scrub with a bristle scrubbing brush for a few minsutes then rinse away with clean water – this is a garden so use a hose pipe and clear that acid wash away.

    Let it dry and repeat – do this several times, each time taking a tiny thin layer off the tiles, then rinse away again (the risning is the key part – imagine washing your hair with way too much industrial-strength salon shampoo, and not rinsing! – this is what contractors tend to do with acids). You may have to get down on your hands and knees to pay more detailed attention tothe noks and crannies but I am sure you will get there.

    I do not think the acid has done anything to the sealer, the HG impregnator, [or any brand] could not have prevented this as it is on top of the sealer. There is a slight chance that the impregnator has not penetrated the very dense slate, just sat on the top, therefore not properly bonded and in this case the acid wash could take some of it off and possibly turn some of it dull/white in which case stripping the sealer may cure the problem. However I think the first situation is morem likely.

    Hope this hleps


  67. tom mcculloch | Nov 9, 2011 | Reply

    many thanks for the good advice, i have applied vinegar as a means of bringing the slate to a uniform dull slate grey finish with no signs now of unsightly staining. i do not think there is any trace of the wd 40 left. what steps should i now take to seal the slate i have some filastone plus purchased for some granite sealing just recently would that seal the slate or what would you recommend?

  68. Ian Taylor | Nov 11, 2011 | Reply

    Hi Tom,

    Well I am not sure I recommend using vinengar! but, if it has worked, I can only asume the WD40 was not deepley embeded in the slate (and that perhaps even soapy water might have removed it).

    However, all seems well so just make suire there are no traces of the vinegar left and that it is perectly dry before sealing. I have never used the product you mention but it appears to be an impregnatiung sealer that also enhances. I cannot think why it would not be suitable, but I would just double check witht the supplier.

    Hope that helps

  69. Chris | Nov 13, 2011 | Reply

    Hi Ian

    I have black slate floor tiles in my bathroom, presumably sealed by previous owner as there is a bottle of sealant left under the sink!

    Over time, water from the shower spilling onto the floor has left white marks on the tiles, and I have tried using general detergent and soap powder and using a toothbrush on the tiles, and nothing seems to be removing the white stains.

    What can I use to remove the white stains, and how can I make the black slate tiles look ‘clean’ with a sheen?

    Many grateful thanks for your advice!

    Best wishes

  70. Clare | Nov 14, 2011 | Reply

    I have found your site and hope you can help me!

    I have had a grey riven (chinese!) slate laid in my entrance hall and utility room – the tiles were very mixed colours as you would expect. They were sealed properly by the tiler.

    We used the cleaner given to us by the tiler and after the first wash a white blotchy, bloom appeared on some of the tiles – it was very noticeable and I asked the tiler to come and look at it.

    They stripped some of the tiles as they thought that they were not sealed properly – I am not sure of the product they used but the smell was overpowering in the house (running eyes etc) and they used a scrubbing brush to remove the sealant.

    Now the tiles that they treated are very bleached out – one to the point of being silver, and others with white circles on. They are considerably paler than the tiles they left. Some tiles also have a rusty circular marks on. None of the tiles are a uniform colour anymore.

    Help! The tiler is saying that the tiles looked like that when he laid them – not true! Will they come back when he reseals them or has damage been done when they removed the sealer?

    I would really appreciate your help as I feel we are being fobbed off and I am going to end up with a floor that looks like a mess!

    Thanks Ian.

  71. Ian Taylor | Nov 16, 2011 | Reply

    Hi Chris,

    OK first of all the white marks, most likely to be soapscum or calcium type depostits left behind by the water, or a combination of both. Over time it builds up. Also, on a black slate, white marks show quite easily, so even the smallest traces of minerals can quickly appear to be quite noticeable. My guess is that had you got a limestone floor you may not even see them. Black slate is usually quite dense, given that it has been sealed also I am pretty confident that the white marks are just likely to be on the top and shoule be removable.

    You could try a mild abrasive like Microscrub (you can get it on the All For Stone link top right of the site) failing that, the usual route is a very mild acidic cleaner again see AFS – DO NOT USE A BRICK OR HCL BASED ACID. Dilute the cleaner really well (it won’t take much) apply, leave a couple of minutes, then a quick scrub with a white nylon pad, then rinse with clean water. Lastly, dry the area wqith a towel. I would also recomend tis as an ongoing idea, drying the floor before the water splashes can dry and leave behind any deposits.

    As for getting it back to a shine, that depends ion a couple things, what the previous owners sealed th efloor with, and what type of surface the slate has. If the slate is very smooth, or if the slate is well sealed with a good impregnator it will be hard to get a coating sealer to lie flat and bond. IF the slate is textured or riven, and if the slate was previously sealed with a coating sealer then you may be able to apply a new one, for example Seal & FInish Low Sheen or similar.

    Hope this helps


  72. Ian Taylor | Nov 16, 2011 | Reply


    It sounds to me as though the cleaner you were left with was either not suitable for the sealer; partially stripping it on the first wash, or the sealer is not water-safe. After that you say they used a really smelly product to strip the sealer, this sounds like a solvent stripper and from what you describe as being left , I suspect that you have not got damaged tiles, rather damaged sealer: If they applied a coating sealer, and it was quite thick (and shiny) then a stripper may take two or more goes to remove it, the first attempts merely taking a ‘layer’ off the top and leaving some now damaged sealer still to be removed, it is as thought the selaer has been delaminated, a bit like when aged sticky tape is left on a wall then pulled off some weeks/months later, only part of it comes away, leaving a white/dull ‘back’ part behind.

    If this is the case, another attempt with the stripper should completely remove it and then, after the floor has been rinsed and dried, it should be back to the pre-sealed state.

    Hope this helps


  73. Darlene | Nov 22, 2011 | Reply

    Hi Ian,

    So, SO sorry for not thanking you sooner but I thought I’d wait until I’d tried your suggestion

    I’ve now tried the cement residue remover but still no joy

    I now have a horrible feeling that I have 40 tiles to fine sand by hand!!

    It seems to be the only way to remove the white ‘bloom’ and as an electrical sander smooths the lovely roughish surface then I can’t use that either.

    So, it’s grab a cushion and every weekend I’ll be sitting out there doing a tile at a time :0|

    Really appreciate your help though, it was worth a try

    Kind regards

  74. Ian Taylor | Nov 28, 2011 | Reply


    you could try an undlited strengh of the same acid, allow it to dwell a bit longer and use a soft wire brush. If when using it neat, you do not see any fizzing, then the acid is not reacing with the cement, (which means it is not doing anything) so you may need to try a solvent (to break down some polymers first)

    Feel frre to email me via the site.


  75. Karen | Nov 30, 2011 | Reply

    We had a ‘professional’ out yesterday to clean our 15 yr old natural slate tile floor. The tiles had what appeared to be condensation residue from mineral deposits where our humidifier sits in the winter. The floor had not been re-sealed since installation.

    The guy used diluted muriatic acid and scrubbed the floor with a wire brush. Now, the entire floor is discolored and there are what appear to be salts in the grout.

    He is to return today to apply a ‘shiny’ (his word) sealer. Needless to say we are less than satisfied. We couldn’t believe how badly the floor looked. Other than applying this mystery sealer that ‘might’ work to get rid of the discolorations and restore the color, his suggestions ranged from renting a machine to installing a new floor.

    I can send a picture. I don’t know what the original sealer was. We would greatly appreciate your opinion. We should have gone with a company instead of an individual recommended by the tile store.


  76. Ian Taylor | Nov 30, 2011 | Reply

    Hi Karen,

    Sorry to hear this, I take it from your use of the word muriatic, you are in the USA, in Europe we refer to the acid as hydrchloric – either way, it is nasty stuff and WAY over the top for removal of a little bit of mineral deposits. better to use a phosphoric acid-based cleaner or similar that may need to be used more than one rather than the ‘sledge-hammer to crack a walnut’ approach of muriatic.

    Depening on the type of slate you have, and its mineral composition, you may have suffered some permanant damage/etching – hard to say from email alone. (If you have really bad etching you may have to call on a stone floor professional to see about having the floor re-ground/re-finished)

    Regarding the salts in the grout – probably true; I’ll preface this by stating that I am NOT a chemist but basically if you react an acid with an alkalie, (base) you tend to get a salt, plus carbon dioxide and water as the result.

    In the case of Muriatic on grout – we are essentially dealing with hydrochloric acid and cement, or mainly calcium carbonate (alkaline) – by exposing the calcium carbonate to the muriatic we get water, CO2 and a salt called calcium-chloride. The salt is harmless enough but, we have replaced some of the cement in the grout (which holds it together) with a salt, (which does nothing). So we have degraded the structure and integrity of the grout, possibly leading to premature cracking and erosion. the salts will wash out with a mild, and far less destructive diluted phosphoric wash but they will leave holes. Also the etching process has roughened up the surface, which has the optical effect of lightening the colour of the grout (rough surface scatters light like the saw-cut face of a stone Vs a polished one).

    The etching may tone down over time with use and washing etc but it may take a while.

    I would ask if, when wet, the floor (slate and grout) looks better or even acceptable, if it does then the proposed coating sealer MAY help, at least a little – only a test in an inconspicuos area will tell, but my advice is to not let him off the hook in terms of responsibility until you have thoroughly tested this. If wetting does improve the look then you may be better with a good enhancing selaer, in the USA, you could use Enrich n Seal by Aqua Mix ( I would call their tech services and explain) it is an excellent product for this and will darken the slate and the grout. however it is NOT SHINY, if you want a gloss you will have to go the coating sealer route, you cannot add a gloss to the Enrich n Seal route – (it is such a good sealer that no coating will sit on it correctly)

    Hope that was some help


  77. Karen | Nov 30, 2011 | Reply

    Thanks so much for your well informed and immediate response! Yes, we are in the US. Yes, the floor looks better/probably acceptable when wet with water. We are not looking for a shiny finish. I don’t know the type of slate but it does have a rough (natural) finish.

    We are allowing him to come out and test a small area behind where the fridge sits this morning.

    As a note, after reading your posts I ran into the kitchen only to discover the finish on my relatively new KitchenAid stainless steel mixing bowl and the stainless steel tray on our kitchen scale is permanently damaged from the fumes.

    I would definitely consider the etching on the tile ‘really bad’. It appears in the ‘grain’ of every tile. The grout isn’t so bad, only a few places that are white which were previously dark gray.

    Thank you again for your time and for sharing your knowledge.


  78. Karen | Nov 30, 2011 | Reply

    I thought it worth posting that we may have solved the problem. Our guy brought a bottle of TileLab Heavy-Duty Cleaner Stripper. Before applying it we called the company and based on our info they recommended applying it full strength to a test area and waiting 15 minutes before using a scrubber then sponging it up with a clean, wet sponge. So far, it looks like it is working beautifully.

    The problem: WAX! And by figuring this out and by not charging us for yesterday’s work and product, he redeemed himself.

    Apparently, years ago the floor was heavily waxed. The product is working much like a wood finish stripper. We can see the wax sort of bubbling up off the surface.

    Also, our guy brought with him a bottle of Aqua Mix Enhancer (seeing that also restored our confidence) as well as Stonetech Impregnator Pro Sealer.

    After reading your response to the pinned forum post, ‘Slate- Sealer Disaster, advice needed urgently’ and I have a question. Given this is a high traffic kitchen floor, the main entry into the house and mud/snow/ everything room, would you recommend the coating over the impregnator?

    Thank you,


  79. Ian Taylor | Nov 30, 2011 | Reply

    Hi Karen,

    Thanks for coming back with this – it great to have a happy ending!

    Wax! – OK, well it is hard to second guess what has gone on in the past sometimes. Well the Tile lab should do a good job of removing it, might need two goes plus make sure he rinses it WELL and then dries it.

    As for the enhacning sealer – if it is your intention to use thisn then DO NOT try to put a coating sealer on top – if using the enhancer it is a case of using it on it’s own, and furthermore the floor must be bone dry before you do it. Even with the other impregnator, you will find that a coating sealer may not want to bond on top – so it is either or, depending on whether you want a gloss finish ir not, bear in mind also, that a coating sealer will require more frequent maintenance and reapplication.

    As for redeeming himself, what about your stainless-steelwork?

    Glad it worked out


  80. Karen | Nov 30, 2011 | Reply

    Thanks, Ian. I’ll go with the impregnator. He is definitely getting his money’s worth out of his knee pads and he’s gone through at least 40 gallons of water!

    He offered to polish the stainless “or whatever I can do to make it right”. He is busting it so hard right now that I hesitate to bring it up again until he’s done.

    Happy to refer any and all who have an interest in stone/tile to your site.

    Take care,


  81. Ian Taylor | Nov 30, 2011 | Reply

    Hi Karen,

    Great news, sounds like he is a hard working, reliable guy, just made an honest mistake (happens to all of us), cudos to him for seeing it through, and to you for giving him the chance.

    take care


  82. Tracey | Dec 27, 2011 | Reply

    Wondering if you could help. We have had a stove fitted with a smooth slate hearth. A bottle of red wine has been dropped on the hearth and where it has spilt the slate has gone a paler colour to the rest of the hearth. It was cleaned straight away with washing up liquid and water. After reading the rest of your blogs I think it may have been etched??
    Many thanks

  83. Ian Taylor | Dec 30, 2011 | Reply

    Hi Tracy,

    Many slates are not known for their susceptibility to acid etching, but some of course can etch. So yes it is possible that the acid in th wine has etched the colour and made it a little lighter. If the surfacce feels a little more dull or powdery than the parts that remain ok, then that is another sign of etching. Also, some slates have components that are not 100% ‘fixed’ in the stone, so colour pigment could be mobile – meaning that with a concentrated cleaner, or an acidic liquid like the wine, could strip out some of the colour.

    It is hard to say without seeing it, but it may get better over time. You may be able to use fine sand paper/emery paper with a little water (wet & dry paper and gently blend the etches back into somthing close to the rest of the slate.

    It may be possible that an enhancng sealer could darken the patches down again and make everything look more even, provided the slate has never been sealed with anything previously. If the slate looks ‘nice when wet’ then this may be something to consider.

    Hope this helps


  84. Karen Stevens | Jan 4, 2012 | Reply


    Great site but my mind is doing overtime on what to do.

    I have grey slate flooring in the kitchen (Homebase), which was laid approx 6 years ago. It has never been sealed, and has been fine up until now. It now has a few water marks and in general is looking a bit dull. I was wondering which product would be best to use for a deep all over clean (floor area 10’x 18′).
    Thanking you in advance for any advice.

  85. Ian Taylor | Jan 6, 2012 | Reply

    Hi Karwen,

    this sounds like a standard periodic deep clean is allthat is needed. Over time slate will get grubby, and I suspect that 90% of the lack-lustre look is dowmn to a build up of the tiniest traces of both dirt and detergent residue that has built up a ‘patina’ over the last 6 years.

    Use a good high alkaline cleaner like heavy Duty Tile & Grout Cleaner (see All for Stone ad on right). Pre wet the floor, then mix your cleaner say 4:1 with warm water, apply it to the floor and leave it for 15 minutes, without allowing it to dry out. Scrub, EXTRACT (mop or wet vac) RINSE – with clean water, and extract that, lastly polish dry with an old towel.

    At this pount if both the slate and the grout joints have come up clean, when dry, you may consider a sealer.

    Hope this helps


  86. Emma W | Jan 15, 2012 | Reply

    Wow chuffed i stumbled across this page, you sound very knowledgeable.
    Ok so here goes…..

    We have just been given an old slate bed of a snooker table, we are going to use this as a fire hearth. I would like to try and bring it to a darker colour as it is light grey. Do you have any suggestions as what we can use to
    : Clean it
    : Buff/Polish
    : Darken
    :Seal it

    Thank you very much for your time

  87. Ian Taylor | Jan 16, 2012 | Reply

    Hi Emma, lucky you!

    Having never removed the felt off a snooker table I do not know what may be on the slate, but expect it was glued down with somthing so there may be residues of a glue. Try a least aggressive to most aggressive approach.

    First try the least aggressive/most gentle method and if that does not work, move up to somthing a bit more aggressive.

    So, I would first just try a mild soapy detergent – like washing up liquid with plenty of water, and a WHITE scrub pad the type for scouring dishes (often white nylon pad on green sponge?) DON’T use the GREEN scourers as they are a bit more coarse.

    if this does not clean it, then use a high alkaline detergent instead, if that does not work, then you may have to go to a stripper like Sealer and Adhesive Remover. (see All for Stone opposite).

    When well rinsed and dry you can look to seal. Notice when cleaning it, if the wetting action made it go much darker, and darker in a desirable way. If so and this is the effect you want, then look to an enhancing sealer (such as Enrich n Seal), make sure the slate is 100% dry before you apply it, and do not leve it looking wet – even if you like the look of it, apply the enrich n seal to a dry stone, leave it to penetrate for 5 to 10 minutes then buff dry to leave a matt finish.

    Give this a few days to fully cure, you will not be able to put a gloss coat on top but you could apply a buffing polish like ‘Brilliance’

    hope this helps


  88. Sue | Jan 19, 2012 | Reply

    Hi Ian,Glad to have found your helpful site. We have just purchased from the reclaimation yard a piece of slate for a hearth. It looks to have been a previous hearth and has some rust stains and gloss paint marks which we hope to remove! Do you have any ideas for cleaning please and sealing.
    Many thanks

  89. Sharon | Jan 19, 2012 | Reply

    Hi Ian,
    We have an en-suite shower made from black slate tiles. It was proffessionally done, sealed, grouted etc.
    We ended up renting our house out and the previous tenants didn’t seem so particular about cleaning. We now have what looks like limescale covering all the tiles (it’s a grey appearance). We have tried limescale cleaners but had no joy, is there anyway we can paint the tiles back to black and then re-seal them?
    Thank you for your help.

  90. Ian Taylor | Jan 23, 2012 | Reply

    Hi Sue,,

    OK, for rust typically go for a very mild phosphoric acid type cleaner, use dilute with water, may take several applications. Only other thing to say is that this is usually effective only for surface rust deposits (rust that has been left on the surface) should you have rust from within the stone due to minerals contained in the slate, then this may not be easy or even possible to remove.

    For paint, use a spaint stripper or solvent if it is thick and stubborn.

    Having said that often paint is relatively ‘new’ as a contaminant, so may be on top of a layer of general dirt and so may well come off with a normal deep clean (it comes away with the dirt that it is stuck to)

    What do yo have most of? – paint, rust, genral dirt? – if it is just in need of a general deep clean, with a few spots of rust and paint, then go for an alkaline cleaner, you may well find the rust and paint come off duinrg the cleaning process, particularly if you boost the cleaner with Microscrub. If not then tackle them in isolation afterwards.

    If you need them here is a list of suitable products, avaiable from All For Stone (click link:

    1. Heavy Duty Tile & Grout Cleaner
    2. Microscrub
    3. Phosphoric acid Cleaner/substitute (or Exrtreme for really bad rust)
    4. Seal & Coating Remover (powerful but safe solvent)

    for sealing, I am guessing that the surface is smooth, or honed. In which case avoid a coating sealer, use an impregnator that leaves no surface coating. Choose either a no-colour natural sealer or an enhancing sealer if you wish to permanatly bring out the colour

    Hope this helps


  91. Ian Taylor | Jan 23, 2012 | Reply

    Hi Sharon,

    Limescale (and soap-scum) can indeed leave a greyish depositi on the slate. The good news is that it is on the slate and therefore should come off, leaving the real slate behind. Unless, it is acid damage to the actual slate but I am guessing this is less likely.

    The limecale removers you may have tried are probably acids, they work by reacting with and disolving the mineral deposit, but they have to be used correctly: leave on the slate for a short period, not long, usually a few minutes, do not allow them to dry out, scrub with a scrub pad, then the all important part, RINSE well with cleanwater. then I would dry them down with a towel.


    the acids used for this are often, Phosphoric, Citric or sulfamic. These are relatively weak in solutions that are available to the public and that may mean several applications. In deed thick layers of limescale may look worse after one slight cleane, or even a couple of inccorrectly executed ones, as the acid may have a) been left to dry (and thus not achieved much) b) reacted with the limecale and produced a halrmless slat as a by product, which is now also ontop of the slate or c) has removed say half or a third of the deposit, like taking only one layer of skin away with dermabrasion etc, so additional cleans, done properly with the right product may well help follow my procedure below for this:

    1. pre wet the slate with plain water (stops acid from drying to quickly, keeps it at the surface)
    2. mix correct solution of limecale remover (or use Phosphoric ACid Cleaner) as per ionstructions, apply to slate. walls may need you to keep reapplying it due to the efffects of gravity, use a spray bottle
    3. leave for a few minuts, keep wet with more solution
    4. scrubb hard for several minutes
    5. RINSE WELL WITH FRESH WATER – easy in a shower.
    6. Dry walls with towels – removes all water and any traces of calcium or other deposits tha may be in the water.
    7. inspect when dry and repeat if required.

    Hope this hlpes, as far as sealing goes, if they have been presealed, then I suggest topping up with the original sealer if possilbe



  92. Sue | Jan 26, 2012 | Reply

    Thanks Ian, we will give it a try.

  93. Morag | Jan 26, 2012 | Reply

    Hi Ian,

    I hope that you can help me. Last year we purchased a black Caithness slate hearth. It was left in our garden for a number of months while we renovated and unfortunately it has now turned predominately brown. Any ideas on how we can restore it back to the original colour?

    Many thanks,

  94. Ian Taylor | Jan 27, 2012 | Reply

    Hi Morag,

    Just incase it is this simple, try a good scrub with a mild detergent, or with the tiniest bit of bleach in water (try a very small test spot) I am just thinking that if it has been out in the damp, it is is possible that it has just got coated with some brown mildew or algea type organism.

    However, it could also be oxidisation (i.e. rust). From what I understand, Caithness stone is actually a kind of siltstone, rather than a slate, they are both very similar types of rock and contain simmilar clays/silts etc and the minerals that often go with them.

    It is quite possible that some form of iron mineral is present. If there is a lot of iron present, then inside the stone, away from moisture and air, it will stay fine, but when a new surface is exposed (in other words when the slate is cut and polished or finished) some fresh iron may be exposed. As it has been outside in the rain and got wet for long periods, there has been ample time for the iron to react with the water and oygen in the air, so it begins to oxize, producing the ‘rust’ colour.

    You may have some success with a very mild phosphoric based acid cleaner – suggest (pending results of first test above) that you try to get some Phosphoric acid cleaner from All for Stone or similar. Use dilute on pre-wetted stone, agitate andrinse, then dry off

    Hope this helps


  95. Liz | Feb 1, 2012 | Reply

    Ian, We recently had a black slate floor installed. It was sealed at the time of installation. The coloration was inspected and found to be fairly uniform. A couple of months later, while the house was still under construction, metallic gold deposits suddenly appeared on a number of the tiles. The deposits were random and appeared in more than one location on the floor. The deposits have a different (rougher) texture than the rest of the tile and it looks like something spilled, but the installer says it’s a natural part of the stone. Have you ever heard of natural metallic deposits suddenly appearing in sealed slate? Thanks for your thoughts.

  96. Dawn Clarke | Feb 1, 2012 | Reply

    Hi Ian,

    can you recommend a slate cleaner brand? I can’t seem to find any floor cleaner that expicitly says is suitable for slate and have ran out of the cleaner we were given when the floor was laid.

    We have slate flooring in our entrance hall, utility and kitchen as we were advised by our builder that it was extremely durable.

    I’ve unfortunately found it quite difficult to keep clean (even though it was sealed twice) and it doesn’t seem to matter how much I clean, but the floor still looks dull with persistent marks. Do you have any advise on how to tackle this?

    Many thanks,


  97. Ian Taylor | Feb 6, 2012 | Reply

    Hi Liz, those natural metalic deposits sound like rust – and yes it is very common.

    Two possible reasons, one is somewhat more obvious to spot, and that is simply somthing above the slate that is rusty, like a metal bucket, maybe a haning basket made of metal that has water drippig from it, some other fixture or fitting that is rusting and is either in contact with the floor itself, or has water coming fro it that is.

    The other and perhaps more common situation is that minerals within the slate itself are oxidising. Slate is made up of many original components like clay, and these can contain minerals, and sources of iron in one form or another. When the slate is first cut and finished into tiles, a new, fresh split face is exposed. Up to this point that part of the slate was ‘inside’ the stone, not exposed to oxygen and moisture

    Now the slate face has been exposed to both, and any hitherto invisible iron-bearing mineral, has been allowed to react with water and air, the moisture can come from above – cleaning and washing, or from below (rising moisture, most slates are pretty impervious so moisture travelling up through them from below is less likely), or from installation, there is a lot of water in grout, and maybe moisture from the sealant?

    So any number of reason but, often slates like this will simply react with the ambient moisture within the air over time, and so this I think is the most likely explanation – the iron-bearing minerals, now exposed, have over a small period of time begon to oxidise or rust -hence the colour and rough feeling.

    Much of this will rub off, and you could reduce it with a little dilute phosphoric acid cleaner – but it may come back over time, however each time you clean it it may reduce in intensity and take longer t come back. You may or may not eradicate it completely. It is however a natural occurance with this type of stone, just like sap coming out of pine, or wood fading or yellowing over time.

    Hope this helps

  98. Ian Taylor | Feb 6, 2012 | Reply

    Hi Dawn,

    One of the reasons that you won’t find a dedicated ‘slate seaerl’ is that most stones can be treated with similar cleaners and slate is usually pretty resillient stuff.

    Look for a general mild, neutral cleaner that says it is ok for tiles and stone for regular cleaning.

    Apart from that, use a mild to medium alkaline cleaner like Xtreme Clean by All For Stonefor deeper cleaning.

    Try to avoid acid based cleaners.

    The dullness you report may be a reulst of the original sealer wearing down -this is normal for coating sealers, or it could be a build up of detergent, leaving a patina, normally fixed by giving the floor a good deep clean with an alkaline cleaner then rinsing well with water and even rubbing it dry with towels.

    If you had a coating sealer (one that was on top of the slate, that maybe had a sloght sheen to it) and this has worn (through alkaline cleaners and/or wear from foot traffic) then this would account for the dulling and the makrs (as the sealer has gone, so to has the stain protetction) – a good deep clean as detailed above then reseal should fix it. From then on try to use neutral or mild cleaners rethat than alkaline for every day use.

    If it was an impregnating sealer then again it may have diminished a bit so again, deep clean and top up the sealer when done.

    Hope this helps, if you have further questions please feel free to ask, if cou could tel more about the sealer used that may help


  99. steve | Feb 17, 2012 | Reply

    Aaargh! LEMON JUICE! Left by me on our friends beautiful slate kitchen top for an hour or so. I feel completely mortified. Now its very white – etched by the acid? I’ve been through previous answers and seen vinegar and wine – will this be the same or is this a qualitatively different problem?

    Short of dismantling the major part of the kitchen to take the worktop to be refinished, what else can I try? Start with a dilute bleach or other alkali?

    Many thnaks Ian, you are providing a major public service here – third from the top for my Google search! Does that mean you can earn some money selling advertising space here – for stone companies and cleaning products? You deserve it.

    Steve (Brighton)

  100. Trish Whitely | Feb 20, 2012 | Reply

    We have a slightly textured black hearth for an open fire. We did not seal it when it was installed and while using a fire log [which I guess contains parafin] some bits from the log fell onto the hearth leaving dark marks, have tried using washing-up-liquid but it didn’t work. As well as a cleaner could you please suggest a sealant as well.

    Many thanks


  101. Ian Taylor | Feb 20, 2012 | Reply

    Hi Trish,

    It sounds to me as if the dark marks are perhaps the oily fuel from the logs or they could be the burnt residue of that, or burnt residue of sap from the logs. I doubt that the slate (if that is what the stone is) itself has been permanently damaged, but the sooty colour could have got quite deep into the texture and maybe fused it self to the stone.

    If a mild neutral detergent did nothing, next on my list would be a strong alkalie but even that may not work. You may need to try a solvent based cleaner/stripper.

    You could try something like Sealer & Coating Remover (you can get this from All for Stone – see link on side for number) this is a safe-solvent type cleaner, it needs to be left on the stone for some time, at least 30 monites before scrubbing. You could also try adding a little abbrasive cleaner – such as Microscrub (again, All for Stone) don’t add this until the dwell time is up, just before you start to scrub. The combination of the stripper working on any resin type stain with the mild abrasive and nanotechnology of the Microscrub may sort it out.

    If that does not work, then try a more harsh abrasive, such as a honing powder, added in place of the Microscrub

    Last resort would be a product called Extreme – by Aqua Mix – it is no longer being brought into the UK as the company has withdrawn all its products from Europe, but All For Stone have stocks. Extreme is a buffered acid cleaner. It can work well on carbon type deposits with minimal or no damage to the stone. As I do not know the exact type of slate you have I cannot advise this completely free of reservation, at the very least, a small test in an inconspicuous area would be required (as it should for any treatment)

    Hope this helps, if you need more information please come back to me.

    All For stone can advise you on a sealer also, feel frre to send them this answer as background


  102. Ian Taylor | Feb 20, 2012 | Reply

    Hi Steve,

    Any idea what type of slate it is? Slate is one of those stones that has a huge variety in terms of it’s geological age and make up. The ‘old’ slates tend to be darker in colour, stronger, have a higher clay content and less, if any, calcium-type compounds in them (making them less susceptible to acid etching). For this reason, it is this type of slate that is most often used for work tops – Welsh Slate would be a good example.

    However, some younger slates (for example, some stone from India, Africa and China, can be aguably more accurately described by geologists as shale, or siltstone or similar, or slate that has only just become slate, relatiively speaking of course) can contain many more minerals, like Iron bearing minerals that are responsible for the rusty brown colours in many ‘slates’. Some of these slates can contain some degree of calcium-based mineral, or other acid-sensitive compunds. If your friend’s slate has etched then there is some thing like this in it’s make up.

    If it has been etched then all may not be lost. As it is a work top, I am assuming it is a fine-honed surface (so very flat and smooth, almost polished?).

    You don’t say if the slate had been previously sealed, if it has not then treating it with an enhancing sealer may disguise the problem, but you would have to treat the entire stone the same and if they don’t like the darker look that may not be an option.

    If it was sealed, then an enhancing sealer will not penetrate and work. In this case (previously sealed stone) there is a very small chance that applying an enhancing sealer just to the etch mark may help, but I cannot guarantee it. You could try dabbing a little oilve oil over the etched part, rub it in and see what it looks like. If it ‘fixes’ the damage without darkening the surrounding slate, then that is a good indicator that an enhancing sealer will do the same, (of course the oil will wash out). Use an alkaline cleaner to rinse out the oil and try an enhancer.

    One other possibility; some impregnating sealers are acid sensitive themselves: if the slate had been sealed with such a sealer, these are often solvent based, they themselves can darken the slate a bit, the owner may not know as this is how the slate was presented to them. But the acid from th leemon juice may have done nothing to the slate itself, but damaged the sealer and the white markes are the ‘damaged’ sealer still remaining. For this you could try localised stripping of the sealer (may have to do the whole slab though) using a sealer remover – try to find out what product was used and seek their adivce as to the best product to remove it. then when removed, re seal.

    Last resort would be to call in a stone restoration company such as Marbllelife Ltd and get a quote for resurfaceing the stone – this involves diamond grinding and re-honing (like planing and sanding wood to get rid of scratches with progressivley finer grades of paper until you get back to the smooth finish.)

    Hope this helps


  103. Llinos | Mar 5, 2012 | Reply

    Hi, I have just had a Welsh slate floor laid in the kitchen.
    It has been sealed and grouted and I was led to beleive
    that all I had to do to clean the residue (from the grout) was use a mop
    and water. I have tried this as well as using a sponge and drying
    the slates straight away with a towel , however the grey wipe marks
    keep returning. Any advice on what I could try? I’m a little
    nervous as the floor was rather expensive!
    Many thanks

  104. Ian Taylor | Mar 8, 2012 | Reply

    Hi Llinos,

    OK, whoever told you that you could just mop the grout residue was not being truthful, dried on grout residue is not easy to remove at the best of times but on slate it can be really tough. If your slate is riven, and the residue is caught in soe of the crevises then it is even harder. If you r slate is honed (or fine rubbed as Welsh Slate describe it) then it will be easier.

    OK, you could try just a cream abrasive, such as Microscrub – put a little water on the slate, then add a small half cup of microscrub, and use a white nylon emulsifying pad . This is abrasive enough to rub depostits away without damaging the slate.

    Failing that you will have to use a mild phosphoric-based acid cleaner – or similar DO NOT USE A BRICK ACID. Pre wet the floor, add dilute acid cleaner (follow on bottle instructions) and scrub. Then pick up the solution with a mop or wet vac. then, and this is important, with both methods, rinse with fresh water, pick up the rinse water, then rub the floor dry. And in the best traditions of hair-cair – repeat if required.

    Hope this helps


  105. Sandra cassidy | Mar 15, 2012 | Reply

    Have slate at back door. Footprints are showing due to cream that was on someones feet. Any suggestions on what to use to remove would be very helpful. Thank you.

  106. Ian Taylor | Mar 16, 2012 | Reply

    HI Sandra, I take it you mean cream as in the dairy stuff?

    If so a deep clean with an alkaline cleaner like this should help.

    If it has stained the slate then you could try a microabrasive cleaner like microscrub or even a poultice.

    Hope this helps


  107. Anita | Apr 1, 2012 | Reply

    Hi Ian.
    You are obviously very knowledgeable and have helped many people! Thanks for that.

    I have a black slate floor that has had an area rug laid across a large portion for many years. When I pulled it up, you can see the lines from the bottom of the carpet. I have scrubbed the floor with water and a mild detergent twice, but those carpet lines are still very evident. Is this permanent damage or can it be cleaned? What is the best way to clean it? I thought it was just residue from the dry-rotting carpet, but it just will not clean.

    Thanks so much!

  108. Ian Taylor | Apr 2, 2012 | Reply

    Hi Anita

    If you could look at the surface of your slate under a microscop wou would see a tiny micro-texture and I suspect that the carpet backking, (not sure what type it is) has over the years been rubbed well and truly into this texture. As these tiny pores in the surface are microscopic, a detergent may just float over the top. You could try scrubbing more vigorously but also, try to get hod of a product that contains a mild abrasive. If yyou are in teh USA, look for Nanoscrub by Aqua Mix. this might just help get into the testure, its particle size is small enough and also the nanotechnology will help to allow the liquid part of the cleaner better access

    If the backing of the carpet was rubber or some other resinous type base, you may find that a solvetn stripper of some kind is helpful in breaking it down. You mmay need to experiment with these two approaches.

    Hope this helps


  109. Anita | Apr 2, 2012 | Reply

    Thank you! I scrubbed with a brush and baking soda, and that helped. But it didn’t clean it entirely. I suspect I need to repeat, or better yet, get ahold of this product you have described. Thank you so much for your help and quick response!

  110. Michael | Apr 3, 2012 | Reply

    Hi Ian,

    Just been reading through your messages and this is a great blog. Thanks! I’ve absorbed all that you’ve said above but am uncertain whether it applies to my situation. I have a black slate bathroom/wetroom. It was installed five years ago and has a slightly uneven surface. After a shower, the water therefore pools in one quarter of the shower floor and drains very slowly over the day. Obviously over the years there has been a pale build up of limescale. I bought some HG Professional Limescale Cleaner and have given the shower several scrubs/rinses with that. The troublesome slates are a bit darker now and look ‘cleaner’ but now I have very visible white patches in the grout. They are not small and I’m panicing! Should I apply more of the product? Its still fizzing when I put on the product so somethings happening but I have a nasty feeling I might be making it worse! I’m almost tempted to get a heavy duty marker pen and black out the grout! Any help would be hugely appreciated.
    Thank you!


  111. Ian Taylor | Apr 3, 2012 | Reply

    Hi Mike,

    OK, the limescale remover is based on an acid, I cannot say which as you do not give me the actual product name (I think HG have more than one). Acids will remove the limescale and soap scum. They do this by reacting with the akaline residue, this lifts the limescale, revealing the slate underor haze neath, so now you can see the natural colour of the slate, without looking through the thin cloudy ‘veil’ or haze of translucent limescale. So that is all well and good.

    However, when an acid is put on grout, it will also react with the alkaline cement in the grout, dissolving it. The acid-alkaline reaction happens until they neutralise each other, or one or other of them is all used up, the reaction creates two by-products, water and a salt – this is visible as the effective ‘whitening’ of the cement – in other words some of the cement, that reacts with the acid cleaner, will be changed into a salt and this is the white blotchiness you can see. Also, as the reaction dissolves some cement, it is removing it, we call this etching, so it will open up and roughen the surface of the grout – like a fine chemical peel and this too alters the look of the grout as when dry, the light will be scattered more by the relatively rough surface of the etched grout than by the smooth un-etched surface. – no doubt when wet it looks much better?

    over time the whiteness will subdue as the roguh edges get worn down and fill up you could also consider using an enhancing sealer to darken them down again – so make the effect of water, a permanent one.

    Hope this helps


  112. Ewan | Apr 4, 2012 | Reply

    Hi, I have just relaid a dark grey slate floor. I’ve cleaned the floor afterwards with Heavy Duty Slate Cleaner (from B&Q) and this has removed all the grout marks but a number of the tiles are left with marks. These can be mostly scraped off so are just sitting on the surface of the tile, but there are too many to do all this way, and some of the marks are too difficult to remove.

    I think this is tile adhesive left on the tile after laying although i could be wrong. Do you have any suggestions on how to remove this?



  113. Michael | Apr 4, 2012 | Reply

    Thanks so much for your help and wise words, Ian! I think I understand the proces but do I continue then until I have ‘neutralised’ the alkaline in the cement? Its only random patches of the grout not all of it. They seem more pronounced though the more I pour on the limescale remover. Shall I try the HG Grout cleaner instead? Or a combination of the two?

    My HG product is literally called ‘HG Professional Limescale Cleaner’ See at

    Highly concentrated acid cleaner. S.G. : ± 1.13 g/ml pH : ± 1.0 Usage : 20 – 40 m² per litre Active matter : 34% Components : phosphoric acid, sequestering agents, nonionics, solvents, alcohol, oxalic acid, gluconic acid, perfume and water



  114. Ian Taylor | Apr 4, 2012 | Reply

    Hi Mike, I would not conintue, every time you do this technically you are damaging the grout, albeit in a minescule way. If you are thinking, that you can even out the effect by uniformly etching the entire grout, that is a reasonable idea but in prcatice the distribution of cement may not be that uniform, or there may be concetrations of polymers in parts of the grout that inhibit the reaction so you may never get a patch-free look. The Product you used is mild, and safe enough, but it is still an acid and all acids etch.

    Instead I would investigate using an enhancing sealer to darken the grout down

    Hope this helps


  115. Ian Taylor | Apr 4, 2012 | Reply

    Hi Ewan, you probably have a combination of stubborn grout marks and maybe even some tile adhesive. Don’t know the B&Q product but if it is acid based it will have helped by remving a thin film of grout haze, but, it has to be a safe acid that works on thin layers at a time, so if you have thicker layers, or lumps of adhesive – it may take several applications (each time also etching the grout in the joints by the way.

    At the end of the day, there is no magical formula for removing this, if the grout/adhsive was heavily poymer modified then a solvent may help, but all that will do is soften the polymer, and not the cement. Either way, applying your cleaner several times, each time scrubbing hard and maybe using a plastic scraper on the stubborn parts, may be all you can do

    Hope this helps

  116. Ewan | Apr 7, 2012 | Reply

    Hi Ian, many thanks. In the end, using the acidic cleaning solution neat (having tested it on a spare tile first!) and scrubbing very hard did the trick. The tiles look good now.



  117. Geoff | Apr 13, 2012 | Reply

    Have just found massive slate slabs (about 1m by 0.75m) under the carpet of our 170 year old house. Have had them cleaned and sealed. Biggest problem is deterioration of the slabs at their edges (defoliation?). Do you have any idea if there is a product that might “glue” the deteriorating edges and so prevent further breakdown. Thanks for any suggestions.

  118. Liz | Apr 14, 2012 | Reply

    We appreciate you advice, but are still puzzling over the gold markings on our black slate purchased in the US. We are fairly certain they are not rust because there is no water source nearby and the stains don’t look like the examples of rust on slate that we’ve found on the internet. The markings, which appear on only a handful of tiles, look and feel like clusters of metal shavings (or small rectangular crystals) and are bright gold in color. The material is very hard and firmly adhered (embedded?) to the surface of the stone. Wish I could attach a photo to illustrate. If it’s a mineral deposit, do you have any idea what it could be and whether it is typical in slate? Tile supplier says they have never seen it before. Tile installer says it’s part of stone and cannot be removed with cleaning. We were shown several sample pieces prior to making the purchase, but of course none of them had the slightest hint of gold on them.

  119. Kristy | Apr 15, 2012 | Reply

    Hi Ian,
    We just refinished our shower with a dark slate threshold and I went to clean it for the first time and didn’t think about what cleaner I was using. I used a Mr. Clean product and now it is left with significant white porous stains. Is there anyway I can now get rid of this?

  120. Ian Taylor | Apr 17, 2012 | Reply

    Hi Geoff,

    I am struggling to think of a product that may do what you are suggesting. there is one idea I have, and I am thinking out loud here, not tried this but:

    Using a VERY dilute pva (like unibond)or better still an SBR (like Bal Bond) – has to be very watered down, you could try letting some solution of this soak into the grout joints, and hope it will soak in laterally also to the slate edges. Rub it dry so it does not dry on the surface. Let it dry overnight. I have successfully re-bonded loose screeds to concrete bases using this method.

    However obviously you would need to strip back the sealer on both the tlate and the grout in order to do this – but you could do a small test area.

    Hope this helps


  121. Ian Taylor | Apr 17, 2012 | Reply

    Hi Liz,

    OK, what you are describing does not sound like rust (iron oxide) – Although I have to say that the slate does not need to be near a source of water, the iron-bearing mineral can lay deep inside the slate, then when the slate is split (to produce the tiles) it is exposed to the atmosphere and the moisture in that alone can be enough, not to mention the moisture involved in fixing and grouting, then washing – all that can be enough.

    However, you describe small gold, rectangular crystals, this is almost certainly Iron Pyrites – quite common in slate and yes, an absolutely naturally occurring phenominum. Think of it like knots in wood – perfectly natural, I would ask the supplier to just change the few tiles affected as the sample set they showed you had no indication of these natural markings (if you were buying knotty pine the samples would be knotty also, if you wanted pine or other wood free of knots and the samples you saw at purchase were all free of such marks and uniform in appearance, you would put any knotty pieces to one side, use as cuts etc, or, if you have a large proportion of them, take them back).

    You will not be able to remove the crystals without physically digging them out, and that will leave a hole and damage the slate.

    If you google ‘iron pyrites in slate’ in images you will see quite a few:

    Hope this helps


  122. Ian Taylor | Apr 17, 2012 | Reply

    Hi Kirsty,

    I am not familiar with that product here in the UK, (I have no idea if it is basically basic/alkaline, acidic, or solvent) but it could be that you have done one of several things:

    1. if acidic it could have damaged some of the grout, and left a fine film deposit of from the cement on the surface – another clean with a very dilute acidic cleaner follwod by plentiful rinsing with fresh water and towelling dry may help
    2. Again, if the cleaner is acidic, it may be that you had a grout haze on the slate that was not that noticeble and you have now partially removed it, making it look temporarily worse – again try repeating the above process in a small area
    3. if solvent or alkaline and you have a sealer of come kind on the slate, you may have partially stripped the sealer, leaving damaged sealer behind – you would have to strip and start again if this were the case.
    4. maybe just a deposit left from the cleaner, due to not rinsing, – try the solution in # 1.

    Just some ideas that come to mind

    Hope they help


  123. Emma | Apr 21, 2012 | Reply

    Hi Ian
    We bought this house in Brisbane, Australia about 3 years ago and the previous owners had smoothed/ground down the slate and I am not sure what sealer they put over it.
    The slate is very light almost white and is very cool in summer.
    My problem is that something is staining the slate and leaving ugly grey marks on it. I think it is water as I have noticed that when water is left on it for a period of time, it stains it.
    So my questions are:
    1. How to remove these stains
    2. For general cleaning, what can I use. Is a steamer ok or does that wreck the sealer?
    Thanks in advance

  124. Ian Taylor | Apr 29, 2012 | Reply

    Hi Emma,

    I am not sure of the type of your slate, most slates are darker in colour but it could be a slate. If you are getting marks just from water, then I don’t think there is much if any effective sealer left in the stone.

    A good impregnating sealer will help, although you will stil get some surface wetting, the sealer will keep stains close to the top long enough for you to clean them. It is still important to react to stains right away, even with a sealer – all sealers do is buy you time.

    The marks are left when contaminants disolved in the water are left behind when water dries out. A good deep clean should clean them.

    I would suggest, as you are in Brisbane, that you contact Call my good friend A’nge and he can talk you through what you need. He can help identify your stone and the nature of the problem, then supply whatever cleaner and sealer you will need. Given the stone is marking so easily, and that you will be conductiong a a deep-clean, you are going to need to reseal in any case. A steam cleaner may help, I would still use a deep cleaner first, maybe use the steam cleaner to help you rinse.

    Hope this helps


  125. rick | May 1, 2012 | Reply

    hi there,i installed a slate floor around a year ago,i put on a neutral sealer, the floor is brazilian blue/grey slate, ive had so much building work going on that the floor is really scratched all over, what would you recomend to strip it back?? also i want to seal it with a glossy/wet look sealer,any ideas would be greatfully recieved.many thanks rick

  126. Adele Goodfellow | May 3, 2012 | Reply

    Dear Ian Taylor,

    I have read lots of your previous comments going back to 2008, which I have found very useful! We have welsh riven slate tiles (of blue/grey colour) which were laid on the floor in our kitchen, dining/ family room area and continuing outside onto the patio. At the time we did not pay too much attention to getting the grout off or the sealant we used. We used Lithofin Slate Seal on the inside tiles and Thompson’s One Coat Patio & Block Paving Seal outside patio. We really liked the wet-look shine of the slate sealer when it was first done, albeit does show up the dust terribly! Fast forward almost 3 years and the slate is looking grubby, particularly in the kitchen area and is scuffed and scratched around the dinning table. I know from reading your previous advice to others that we need to use a Phosphoric based acid cleaner, lots of scrubbing with nylon brushes/ pads and plastic scraper, mop/vac up and rinse and dry in order to get muck, grout and any old sealer which may be left up. My questions are:
    1. Could you recommend a particular cleaning product for this job?
    2. Is the Lithofin Slate Seal a good quality product, or is there something better and more hard wearing we could use? Or should we be using a sealer which soaks into the tile instead?
    3. Once we have fully cleaned and re sealed, what should the ongoing maintenance be to keep it looking good for longer? Eg dusting/vac floor mopping with only water?
    4. How often should we be putting on sealant, can this be put straight on top of previous layers once cleaned up properly?
    5. What do you suggest for the outside tiles?

    Many thanks for your time,


    Adele Goodfellow

  127. Jackie | May 4, 2012 | Reply

    Hi Ian
    My husband has just installed a new piece of welsh slate for the hearth which has not been sealed. On delivery it was left outside the door on a wooden pallat and shrink wrapped. It has dark areas which look to me as though something has been spilt on it. My husband thinks that this is natural but I’m not convinced especially has there has been some mild improvement since cleaning with Liberon stone floor cleaner. After reading your blog, I’m just about to try cleaning with washing up liquid and warm water but do you have any other advice.

  128. Jackie | May 4, 2012 | Reply

    Hi further to my previous comment the darkened areas feel rough (we had asked for a flat finish or is that fine rubbed?)and slightly raised.

  129. Ian Taylor | May 11, 2012 | Reply

    HI Rick,

    OK, well with all that work I imagine that it is the slate that is scratched not just eh sealer. You can strip back the sealer with a standard sealer remover/stripper (such as Sealer & Adhesive Remover or equivalent – a solvent based product.). Rinse well and allow to dry completely.

    When dry see if the scartaches are still an issue (you may find that the scrubbing and stripping priocess makes them acceptable). If the slate is honed then applying a wet look/sheen finish may not be possible. However if the slate has a natural riven fisnish then it ought to be OK. In the case of a riven finish I would recommend something like Seal & Finish Low Sheen. Try the link to All for Stone.

    Hope this helps


  130. Ian Taylor | May 11, 2012 | Reply

    Hi Adele, Lot of questons there I will try to answer them in the order in which they were asked:

    First of all though, before you use an acidic cleaner (I assume you meant for the grout residue?) you will need to remove the remaining Lithofin Slate Seal. You will need a stripper for that, you could try Sealer & Coating Remover, or try whatever product Lithofin recommend for its removal. Then you can follow the advice for removeing any grout residue (although you may find some of it coming away as part of the stripping process)

    OK, Q1. Oops, I hink I answered that above

    Q2. Yes, to my knowledge it is a very good sealer. Is it the best? – hard to say. I can recommend an alternative in Seal & Finish Low Sheen (available via All for Stone) is it harder wearing than Lithofin- I don’t really know, maybe, perhaps just a bit, but the main differenence is it is water based and much nicer to apply. But they are both topical sealers and will therefore wear and so in a high traffic area they will need frequent reapplication, I think that the 3 years you have had the Lithfin on for is the very max limit for this type of sealer. You may be better reapplying every year.

    Q3. You pretty much answered this yourself, keep grit off the floor (dust mats) sweep vacuum regularly, Mop up isolated spillages as teh occur, use a mild eutral cleaner for every day or routine washing. Avoid using harsh cleaners. Alkaline cleaners will remove some coating sealers or at least dull them severely.

    Q4. As often as required. I cannot speak for the Lithofin product but the Seal and Finish Low Sheen can be applied to itself wiothout theneed for stripping back. As you are going to have to strip the floor anyway there should be no problem putting any coating sealer down.

    Q5. For outside I would use a good impregnating sealer, the external environment is too harsh for a coating sealer.

    hope this helps


  131. Ian Taylor | May 11, 2012 | Reply

    Hi Jackie,

    Sounds like stain of some kind, if washing up liquid does not help, try an alkaline cleaner, you could also try a poultice

    hope this helps


  132. Ian Taylor | May 11, 2012 | Reply

    Hi Jackie,

    OK, it sounds as though you have got a riven finish – a natural finish where the slate is left as it is when it is split. This can be very smooth but with the occasional bump or it can be an all over texture. This variation oin the surface could well be naturally varied in colour also. It sounds to me as if you had wanted a fine rubbed (honed) finish – where the slate is ground to a very smmoth and flat surface. I would double check this with your supplier. You could still have patches of darker or ligher colour in it though.

    Hope this helps


  133. Steven Bryan | May 24, 2012 | Reply

    I have just laid a brazilian natural slate floor and it has been sealed with Lithofin.
    My client is complaining that when you walk on it, you can see footprints from trainers. (It was sealed 4 weeks ago).
    Is there anything I can do to stop this?
    Many thanks

  134. Ian Taylor | May 30, 2012 | Reply

    Hi Steven,

    Unfortuantley you do not identify the actual Lithofin product. So, I do not even know if we are talking about a pentrating type sealer or a coating.

    If a coating (like multi seal or slate seal) then you are leaving a top coat of sealer, it should not act as you have decribed, if it has, something is wrong, possibly that too much was applied, or the stone was too dense to recieve it in the frst place (smooth surface, non porous and/or presence of some previous sealer remaining – the latter unlikely in a new floor I admit) and this has preveneted it from drying correctly (it can skin and remain sticky). If this is the case, it will need stripping back and redoing (if it is possible to do it due to the density/porosity of the stone).

    If a penetrating type sealerwas used, then again soemthing similar could have happened, in that too much can be applied, leaving a residue at the surface which is not supposed to be there (so you will leave foot prints) or (less likely I think) not enough has been appplied so the stone is not quite sealed enough.

    hard to say from the infomration provided but hopefully I have given you some things to investigate

    Hope it helps

  135. Darlene | Jun 7, 2012 | Reply

    We have a green slate floor in the shower and around bath and sink. It is sealed, but our water leaves white marks on it. It is well water with a water treatment system and added calcite. The calcium is easy to clean on stainless steel and any other surface, but for some reason it seems like the slate has absorbed it. Once I tried vinegar to clean it on the slate, since this works in our kettle and dishwasher, but it made things worse as well as making the grey grout white. Sometimes I put mineral oil on the stains to hide them, this lasts a month and then they are visible again. We have purchased a special stripper and sealer that is apparently really good from the slate dealer. But wanted to see if there is anything else I can do before I go that route. We had sealed the tile really good when it was installed, even a few times; this problem started a month after sealing it. I don’t want to have to go through all this trouble, if the same thing will happen again. Plus we have a 5 month baby in our house and don’t want him exposed to the fumes of the stripper. Any suggestions on where to begin. I was thinking of using CLR, but worried it might make it worse. The stains seem like they are in the slate, not on the surface.

  136. Ian Taylor | Jun 8, 2012 | Reply

    Hi Darlene,

    I can see your dilema, I do not know CLR, but a quick look makes me think it is an acidic cleaner – so will have a similar effect to vinegar.

    The issue you have is that any cleaner that will break down calcium will be acidic, and any acid will etch – hence the grey grout turning white.

    Why there is only a problem on the slate? – well even a good impregnating sealer leaves the actual surface of the slate exposed, it could just be that the calcium bonds more easily to the surface of the slate through adsorption (as opposed to absorption).

    The mineral oil could be simply masking the problem (and certainly helping to dampen down the white colour back to grey on the grout). But oil is transient, it won’t last, plus the calcium will just sit on top of it anyway.

    You could try an enhacning sealer (does the same job as mineral oil but will be permananent) the only problem is it can be tricky to adequatley remove the exiting sealar, so as to allow the enhancer to get in evenly.

    It might be possible to acid clean again, then use an enhancer just on the grout, then adopt a regime of prevention rather than cure. Use a mild abraisive cleaner such as nanoscrub (I think you can get this in Canada, it is an Aqua Mix Product) – using it frequently before there is build up, to lightly abraid the calcium away.

    Hope this helps


  137. Marie-Hélène Besse | Jun 8, 2012 | Reply

    Hi Ian

    I’ve read lots of your advice to see if it would help me but am still not sure.
    In 2008 I had a Burley flueless gas fire installed and a black polished slate hearth put in. Soon after (and again this week) water seeped in from the chimney flue and now there’s a greyish matt stain on the slate which I can’t shift with the special slate oil I use to clean the slate. The chimney is capped but not blocked and I fear this is going to happen again and again with all the rain we get in England! What can I do to remove the stain? Thanks for your help.

  138. Darlene | Jun 9, 2012 | Reply

    Hi Ian,

    Thanks so much. You have a great blog and it helps so many people. I will try the nanoscrub first to see what kind of residue I can remove first. It sounds like a really good product. The enhancing sealer would be nice if it all works out, our tiles look so much richer with the mineral oil and will be great if we can get the same effect with the sealer.

    Thanks again,

  139. Ian Taylor | Jun 10, 2012 | Reply

    Hi Marie-Hélène,

    OK, I am assuming the slate was also sealed prior to the water getting through?

    Even if not, the fact that the slate is polished and black tells me that it is likely to be a very dense slate. The special cleaing oil, is really just an oil that leaves behind a film that will to some small degree, penetrate and absorb, but also ‘adsorb’ – which just means bond to the surface, then you polish that by buffing – so this will have acted as a bit of a sealer. Using it to clean is a bit of a misnomer, really as it has had some oil already, as a sealer, not much is going to get in to the slate and so wiping away the dirt with more oil is in theory quite easy and at the same time you are keeping the oil topped up or refreshed.

    This is fine but it will not prevent everything, some contaminants will land on top of the slate, (and on top pf the oil) and still manage to bond to the micro textrue of the slate. The marks you describe sound like mineral deposits: water is very ralrely pure, often there are minerals disolved in it. For example, there can be calcium carbonate or other soluble minerals. Also, as the water has seeped through the chimney, running accross bricks and cement, there are other things it can pick up including soot, but also more calclium from the mortar joints among other things.

    The water carries them down and splashes on the slate, the water then evaporates and the minerals being carried get left behind, if they are minerals like caclium (from cement) they will re-form as a fine crystal layer and would be able to bond to the surface to the point where just wiping them with oil will not remeove them.

    You could try rubbing with a white scouring /emulsifying pad. Or try a bit of Microscrub (a powerful abrasive cleaner that will not scatch the slate, or remove any oil that is already inside the slate – may remove some fromm the surface but that is easily replaced afterwards).

    It could be worth checking that it is not acid etching – effectively from acid rain, or water that has become acidic because of what it has picked up along the way. I have to say, I am unsure what the ph of rain-water combined with chimney soot, but if it were acidic and if the slate is sensitive to acids, then you could have some acid etching – where the acidic contaminant actually corrodes the polished surface. Cleaing with oil would not solve this (although it would temporarly mask it, until the oil dries or fades).

    If you can ascertain that the slate is in no-way affected by acids then that rules out etching, and also, it allows you to explre a mild acidic cleaning solution to the mineral deposits – in other words, provided your slate is not affected by acids, a mild acid based cleaner (like phosphoric acid cleaner, or some house hold cleaners that have citric acid, or even viengar for that matter) may help to remove the splash marks. BUT – please ascertain the acid sensitivity of your slate first- by calling the supplier, if they don’t know, ask them for an off-cut, a piece of watse so you can try lemon juice and other acids on it first.

    Regarding this happening all the time, yes unfortunately it will, unless you can stop the water from getting in, but if you find a way to quickly remove it, and you keep the oil refreshed, it should be easily manageable.

    Hope this helps


  140. Jon Kelly | Jun 11, 2012 | Reply

    Hi Ian

    Could you advise, I’ve recently installed a slate floor across my ground floor approx 190 sq meters. The floor is a chinese slate and has been installed on a sand/cement bed with a wet underfloor heating system.

    The problem I have is cleaning the slate as there is a dusty residue that simply keeps drying when I mop the floor.

    I have sealed part of the floor with feb superclear 181 but I think the floor was still damp as this “bloomed” went cloudy, so I cleaned it off with whitw spirit. I’m not sure what to do next could you recommend a cleaner (there is still some cement stains on the slate) baring in mind the area that needs cleaning, or a acid that will do the job.

    With thanks


  141. Ian Taylor | Jun 11, 2012 | Reply

    Hi Jon,

    It is not unusual for this type of slate to be dusty when dry, much of it is a much softer slate than say, an indigenous UK slate (like Welsh Slate for example) so there can be some surface dust that will settle down over a short period of time. Also, if it is a multi-colour slate (reds, browns, gold etc) then much of that colour comes from minerals like Iron which has oxidized – so basically it is rust. This ‘rust’ and other oxides can be dusty.

    Some of this rusty dust will wipe off with just plain water (and then more may develop) but some of it is going to need something stronger. Also, the remaining grout/cement residues will need a mild acidic cleaner – one made for the job, not and I repeat NOT a brick acid, based on HCL – way too strong and dangerous. HG Extra or Aqua Mix Phosphoric Acid Substitute are ideal, or there is another product called Extreme (also by Aqua Mix) that is slower to work, but will do less etching damage to the grout joints (all and any acid product will etch, and that means making darker grout joints turn much lighter although they will darken down again over time).

    Aqua Mix is no longer being brought into the UK but there are some stocks left, you can contact Tilinglogistics Ltd on 0121 705 5333.

    One other thing that I highly recommend you do is hire two bits of kit (given that you have 190 m2): A low RPM mono-brush cleaner with a medium hard brush head (low RPM means between 175 and 350). And a good wet vac – make sure the wet-vac has a good and new squeegee head, not one that has been used on over a thousand building sites.

    Procedures may differ from product to product but for the Extreme (which I think I would suggest) it would be like this:

    1. Mask off and protect any adjacent surface from contact with both the acidic cleaner and water.
    2. Sweep or vacuum your floor to remove loose dust
    3. PRE-wet the floor by mopping with clean water (allows proper wetting action of cleaner, prevents cleaner from diving too deep into stone, and keeps it active for longer)
    4. Apply Extreme, diluted (read on bottle instructions) to a medium-to-weak solution
    5. LEAVE TO DWELL for 30 minutes or longer – keep wet in the mean time
    6. Agitate/scrub with the brush on the machine
    7. Use the wet vac to pick up the solution
    8. Apply fresh, clean water to the floor and agitate with the machine again – this is the rinsing phase and is essential for removing the dirt and traces of the cleaner
    9. Pick up the rinse solution with the wet vac.
    Note, if your mono brush machine has a liquid tank, you can use this to help disperse the cleaner, then again later to disperse the rinse water. Agitate lightly as you go, but do not skip the dwell time, come back and agitate again after the dwell time.

    Allow the floor to thoroughly dry out – especially as there is a sand and cement screed bed.

    A note on the underfloor heating system: For cleaning and sealing it is always best to leave this switched off for the duration, if you cannot turn it off, turn it down and keep the temperature constant. While actually having it on slightly after cleaning may help the floor dry out a little faster, it may also dry it too quickly while you are cleaning and want it to remain wet. More importantly, you need a cool, constant temperature (again preferably off) when sealing, until the sealer has cured.

    So, sealing:, once the floor is clean and dry (and by dry I mean very dry, less than 5% moisture, and after all that cleaning there will be a lot of moisture in the floor to get rid of – so allow it a good few days) you can seal with your chosen sealer. I am not sure if you are looking for a penetrating sealer or a surface coating type, they both had pros and cons, one advantage of the coating types (like Seal & Finish Low Sheen) for example is that they will make cleaning easier, keep the dust better contained from the beginning and impart a low sheen satin finish that will bring some of the natural colours to the fore, without overly enhancing them. The down side is that they will need regular top-ups, depending on traffic, every 6 months to 3 years

    Hope this helps


  142. Debra Beam | Jun 12, 2012 | Reply

    Hello. Have been reading all the post to find an answer to our question. Here is my problem: we just had a slate tile floor installed. The tile guy laid the slate, then put Enrich and Seal on the tile before he grouted the tile. He did not follow the directions on the bottles of Enrich and Seal which say to remove any extra sealer after 5 minutes. The tile felt slimey like soapscum. We were very disappointed in the final look of the tile. At the tile store we told them we wanted a shiney finish. The Enrich and Seal did bring out all the colors but there is no shine so we used a floor stripper which removed the soapscum feel but now we want a shiney finish. We bought TileLab Sealer and Finish / Gloss. It is a Water Base, Acrylic Polymer with Glycol Ether. As I said before we did use a stripper to remove the Enrich and Seal BUT water does still bead on the tile. Can we use this TileLab sealer on the natural slate now since it has been stripped? We are really wanting the glossy finish. Not real happy with the place that recommended the Enrich and Seal because it has no shine to the finish. Thank you so much for your help!

  143. Ian Taylor | Jun 14, 2012 | Reply

    Hi Debra,

    The removal/stripping process you have undertaken has only removed the excess sealer – in other words, it has taken away only the sealer that was left, incorrectly, on the surface. However, it has not taken the sealer out of the stone, as evidenced by the fact that the sealer still beads water.

    The issue you have is this, that sealer is virtually impossible to remove once applied, and it is a really good product in terms of doing its job as a sealer. It is designed to help prevent liquids from penetrating the stone and to keep contaminants out or at least at the very surface. This means that water cannot get into the surface very easily so it sits up in a ‘bead’ or ball. The sealer has effectively massively increased the surface tension of the stone.

    The product you have purchased will not, in my opinion, work on top of the Enrich n Seal. I am not 100% certain of the exact product, but as it is labelled an sealer and finish/gloss – it is likely to be a combined sealer/finish. Bear in mind that Tile Lab is a Custom Building Products Brand – and so is from the same sable as Aqua Mix (who make the Enrich n Seal) and I would imagine that it is very close to the Aqua Mix product that goes by a similar name. These types of products require some porosity and texture to bond and the Enrich n Seal will not be able to distinguish the new sealer from the general liquid contaminants it is designed to keep out – so it will repel the sealer, it will bead just like the water and so won’t lie flat, this means it will dry streaky, if it dries at all, and where it does dry, it just won’t bond so will walk off easily, and look a mess.

    The only thing you could try is a top coat gloss (Aqua Mix make one called Floor Shine & Hardener) or a natural wax. the Floor Shine & Hardener is also water based acrylic gloss coat, however it is not designed to be a sealer also. It will still be a challenge to get it to adhere and lie flat, and I have to say, it may not be possible.

    What you can try:

    You cannot remove the Enrich n Seal, but you do need to try remove or reduce significantly, the high surface tension. One thing you can try is to use a white scrub pad and an alkaline cleaner and really give the floor a good scrub, mop up and then rinse. When it is dry, try a small application of the FS&H (or wax, same goes for that – but wax would become a labor of love, not as easy to maintain as the FS&H). If it lies flat (spreads out nice and evenly with no ‘pulling back’ into ribbons of liquid), then it stands a chance of drying nice with a good finish and bond. If is is still pulling back/beading as you try to apply it, take a new, clean scrub pad and rub it into the FS&H on the floor while is is still wet (as soon as you apply it and it beads) sometimes this will help it to ‘relax’ and flow flat, now use the paint pad or whatever you are using to apply the coating to feather it out.

    If your test works out then you can take the risk of applying it to the whole floor.

    If it does not, another strategy I have seen used is to let the floor be for a while, a few weeks or months, allow time for the natural traffic to begin to wear the high surface tension down a bit, then do the alkaline cleaner scrub and try again. This way the stone surface has become ever so slightly, naturally worn, along with the sealer, (as opposed to you just scrubbing the sealer if that makes sense) Sometimes this works quite well.

    The stone will be fine in the mean time, as it is sealed with a very god product – it just means that you have t live with the lack of shine for a bit longer.

    Hope this helps


  144. Debra Beam | Jun 15, 2012 | Reply


    Thank you so much for the information even though it wasn’t what I wanted to hear. :O( Your explanation was much more clear than anything I have read or been told so far. Thank you for taking the time to answer and to explain it all to me. I should have done more research prior to the tile installion.

    Many Thanks,


  145. Brian | Jun 17, 2012 | Reply


    I have black welsh slate which is sealed on my kitchen floor. I have tried to clean the floor with a new steam cleaner which has left white marks or residue on the tiles. I have immediately stopped using it and wished I and never started. Do you have any advice on what the cause might be and how I can restore the tiles ?



  146. Clandestineaz | Jun 17, 2012 | Reply

    I live in a 1700 sf house that is almost completely tiled in a dark grey textured slate tile with (aparently) light grout. We have a dog and a cat and we live in a desert (DIRT). What can I use to deep clean the tile that has high dirt activity and how do I go about cleaning it? Then, what do I do to not keep it as clean as possible?

  147. Ian Taylor | Jun 18, 2012 | Reply

    Hi Brian,

    I think that the sealer must be a coating type right? If so, I suspect that the steam cleaner has partially broken it down (the heat and water has delaminated the sealer, and made it go milky white and loose its shine). The good news is I strongly suspect that only the sealer is damaged, not the slate. You will need to completely strip the sealer now and reapply it. You may be able to get away with just stripping a section, up to a grout joint, or doorway or somthing.

    Hope this helps


  148. Ian Taylor | Jun 18, 2012 | Reply

    It depends on what the ‘dirt’ is. For a deep clean you typically need a high alkaline cleaner and that amount of sq ft I would definitely consider getting/hiring a rotary scrub brush and a wet vac.

    IF the DIRT is mineral based, and really stubborn then (as you are in the US0 you could try a product by Aqua Mix called Extreme – it is an acid based cleaner that is great on red dust, rust and other similar issues. – so do not mix it with the high alkaline – I suggest try the alkaline route first, if no good try the Extreme.

    Hope this helps


  149. Brian | Jun 18, 2012 | Reply


    Thank you very much for your advice, really appreciate it. We will do it asap and update your forum with the result.



  150. Brandy Sapp | Jun 29, 2012 | Reply

    I just bought a house and the oversized shower has colored slate on walls and floor of shower. The floor is made up of tiny (1 inch x 2 inch) tiles and it is 8′ x 10′. This house has been sitting a long time and in the corners of the shower, it looks dirty, but looks more like white chaulky stuff that is convering up the tiles (kind of gritty too). What can I use to make it look like the tiles in the middle of the shower? They are the ones that get wet and get used and look clean. Thanks!!!

  151. Brian | Jul 1, 2012 | Reply


    Thank you very much, you are a star! Your advice worked perfectly. We wont be using a steam cleaner on the floor again.



  152. Ian Taylor | Jul 3, 2012 | Reply

    It sounds like you have a very mild case of efflorescence. You might be able to remove this with some light abrasive, try some cream abrasive cleaner (nanoscrub if you are in the USA). I have written extensively before on efflorescence so I won’t cover that again, but if the slate is not acid sensitive, you may find that a very dilute wash with a MILD grout haze acid based cleaner (NOT A BRICK ACID or MURIATCI/HCL) will work wonders – DO A TEST first in an part of the shower where it does not matter too much if that is possible, but in any case PRE wet the tiles, the apply a small amount of your cleaning solution after diluting it considerable, leave it a few minutes then scrub, then rinse.

    Now dry the area with a towel and then let it air dry. Hopefully it will work without bleaching away any colour from the slate (or the grout) but this depends on the correct dilution (start at say 10:1 water to cleaner, if it does not work, try 7:1 etc).

    If it is efflorescence you may find that it comes back, treat it straight away with just the nanoscrub and you should be fine. Check also (once clean to your satisfaction) that there is adequate sealer on the slate as this will help prevent more moisture getting in (one of the causes of efflorescence).

    it could also be that you have got cement/grout left on those tiles – well the same remedy as above is what I would try, just might require several goes.

    Hope this helps

  153. Lorraine | Jul 6, 2012 | Reply

    We have a smooth, green, slate hearth which has been stained by a shaving brush containing shaving foam and water being left on it, leaving a white circular mark. We would very much appreciate your advice on how we might be able to remove this stain. Thank you.

  154. Kelly | Jul 8, 2012 | Reply


    We have dark grey ceramic floor tiles in our newly refurbished bathroom, however the builder has stained them with concrete used to build a glass block wall. Since that, when the ceiling was drilled for a new spotlight, more staining has appeared (assume from ceiling dust).
    Can we use the same acid as for the slate you’ve mentioned above?


  155. Ian Taylor | Jul 9, 2012 | Reply

    Hi Lorraine,

    I have written a post on this here

    I suspect you have an oily stain, read the entire post or skip to the paragraph after step 3 whee I talk about using a poultice. It mentions a product that is no longer available in the UK but there are alternatives such as Poultice Pro (available from Tilinglogistics on 0121 705 5333)

    Hope this helps


  156. Ian Taylor | Jul 9, 2012 | Reply

    Hi Kelly,

    I would say this sounds fairly straight forward. You have cement deposits and plaster dust etc – yes a regular mild acid based cleaner for removing grout haze should be fine. Again I stress not to use a brick acid or one based on Hydrochloric acid.

    Just be 100% sure your tiles are glazed and not with a metallic glaze (they are not an faux metal effect, bronze, platinum etc) – if you have a spare tile in storage, just make sure that the cleaner does not damage them.

    You may need several applications – this is fine, be patient it is designed to take small amounts at a time so as to minimize damage to grout joints.

    Hope this helps


  157. Charlotte | Jul 13, 2012 | Reply

    Hi, I live in a 1950’s house in Kent (hard water!) All our internal windowsills are slate tiles, cemented in. Over the years they have gotten paint splats over them (matt and satin wall paint) and what look like water stains. I don’t know if they were ever sealed, they are smooth tiles and mostly matt, although in less used areas they look a little bit more polished. I would love to restore them to their former glory, but I’m on a tight budget. I have stovax slate cleaner and polisher which I applied the other day – they look a little darker and slighty shinier, but no cleaner!
    Thank you!

  158. Ian Taylor | Jul 18, 2012 | Reply

    Hi Charlotte,

    I think (not 100% sure) that the product you have used is more of a maintenance cleaner, and more of a dressing/polish than a cleaner – I am sure it will contain a small trace of wax or oil or similar and this has the effect of slightly darkening the colour and adding a bit of a sheen. I would suggest this could be used after you have got the slate clean – just like using Pledge or Mr Sheen on a wood table.

    To clean the paint splashes you need a solvent, a paint stripper I would suggest perhaps a clear spirit like white spirits, be careful some like turps are a bit oily in nature themselves. The solvent will also remove the cleaner you have put on.

    For removing cement stains you will need an acidic cleaner – get a MILD one from a tile shop, not a brick acid or anything based on HCL.

    Once you have got the slate clean, rinse it well with water and allow it to dry thoroughly. At this point try reapplying your slate cleaner to ‘dress’ them

    Hope this helps


  159. lin | Jul 29, 2012 | Reply


    I have a slate foyer floor that I had sealed many years ago and has stood up wonderfully. Recently I had my rugs cleaned and the tech dripped some solution all over my slate foyer as they were carrying out the equipment. Now I have more than 50 spots from the drips as they walked through the foyer. It took of the sealer in those spots. I have a call into the company but they had to speak to the tech first. I do not know what kind of solution was dripped on it… does anyone know what I need to do ? DO I have to have all the sealer stripped from the floor and resealed? Any suggestions.? Thanks…

  160. Ian Taylor | Jul 30, 2012 | Reply

    Hi Linda,

    OK, this is hard to say from just a message like this but I am thinking it could be one of a couple of things.

    First though, you do not say what type of sealer, coating or impregnating? If a coating and it has lasted many years without intervention – then I am surprised. Before I go on, just check that they have not simply dropped dirty water from their machines and this has left a dull deposit on top of your slate, that is giving the appearance of the seal having gone.

    OK, the logical first thought is that they dripped something alkaline/solvent-based and that this has stripped the sealer. If this is the case, then, basically the sealer in those spots is not gone – so needs replacing. Whether or not you can simply top up the sealer in those spots is debatable – do you know what the original sealer was? do you still have any? if a coating sealer the rest will have worn and so just adding new to the spots won’t look right. My suspicion is that the whole floor will need to be stripped after all this time, and a new seal applied – need not be a huge job though.

    The other possibility here is that things are not what they seem; If the floor was sealed many years ago (and your comment seems to infer that no further top up or repeat sealing has occurred) then I sincerely doubt that a topical/coating sealer was used as it would have long since gone,even an impregnator may no longer be 100% present and effective after all that time. What may have happened is that over the years, with were and traffic, and regular cleaning, the seal, may have slowly degenerated/been worn off, but it was not noticeable as at the same time, a ‘patina’ has been built up – the patina comes from, and there is no nice way of putting this, a mixture of small traces of dirt building up with residues of the cleaning solution that is used, all slowly building up and being ‘polished’ by time and foot traffic into basically a natural coating. To be honest this can look quite nice and give a pleasing effect – a floor that has ‘aged’ nicely if you like. It is just possible that the cleaning solution dripped by your carpet cleaners has cleaned off this patina – so in fact the spots are ‘clean spots’.

    Again in the last scenario, there is only one solution and that is to apply a deep clean to the whole floor – and strip back to the slate surface, to be fair if you have had many years without need of deep cleaning you have done very well. Once you clean it back you will have a choice of ways to reseal/finish the floor.

    Hope this helps


  161. lin | Jul 30, 2012 | Reply

    Thanks for your response.
    I thought it was just a coating sealer. ( I could be wrong). I did wash the slate 2 times after they left thinking it was dirty water.

    I just now found out from the company whos tech spilled that it was cleaning solution . They will be stripping and resealing it. At their cost.

    thanks again for your response.

  162. Joanne | Aug 8, 2012 | Reply

    I have a shower which was tiled in with glazed porcelan tiles, glass tiles, slates tiles and granite. There is no way to isolate any one type of tile to clean and I am not sure what is safe to use on all 4 different types of materials. What cleaner can I safely use on all materials to get rid of soap scum buildup?

  163. Ian Taylor | Aug 13, 2012 | Reply

    Hi Joanne,

    OK, as you have probably deduced, the ‘usual’ treatment for soap scum is a mild acidic cleaner that is designed for such a job, but you are correct to check whether your materials are capable of resisting damage from such cleaners. First of all the glazed porcelain and the glass should have no issues (apart from in some rare cases where there is a metalic glaze) also most slate is resistant to acid cleaners, some of the multi coloured Asian or African slates cna lose a little bit of colour as sometimes the rusty iron deposits (that provide the colour) may be reduced in intensity, but most native US, UK and other European slates (greys, greens, blacks and reds etc) tend to be pretty resistant. Similarly most granites are also acid resistant. However there are some stones sold under the umbrella term ‘granite. which are in fact geologically speaking, not actually granites, (such as basalts) some of these can etch with acidic cleaners.

    So, as with all the advice I give, TEST FIRST – if you have a spare tile for each type, try leaving some neat cleaner (we are talking about mild acid cleaners based on phosphoric or equivalent, not HCL) on them for 5 to 10 minutes. Then rinse away and allow to dry. If no damage, then you will certainly be safe at normal use strength).

    I would also try a cream micro abrasive cleaner like nanoscrub in the USA, or Microscrub in the UK.

    Hope this helps


  164. Karen Clark | Aug 16, 2012 | Reply

    Hello, I have old rabbit urine stains on my floor, I have washed it repeatedly and when wet it returns to original colour but dries white and terrible looking. Please help. Thank you.

  165. Ian Taylor | Aug 20, 2012 | Reply

    Hi Karen,

    OK, this is a bit different, I take it that we are talking about a slate floor? don’t know which kind of slate though. There are two potential things to be concerned about, an actual stain (discoloration left by a contaminant) an etching – physical damage to the surface of the stone by acidic/corrosive compounds.

    Stains from urine ought to be reasonably easy to remove with alkaline detergent or even bleach (diluted) but an etch would leave a permanently damaged surface. This damage (which can affect a few but not all slate types) dulls the surface, by etching away finer particles, leaving the surface changed in colour and flat and lifeless, with the surface often a little rougher to the touch. When wet this temporarily disappears as the water evens out the surface and alters how the light is reflected. when it dries out the effect is lost and the dullness is returned.

    If this is the case, then either the slate surface must be restored (may be possible with fine sand paper, or diamond hand pads – unless the slate surface was riven) or if no other sealer has been used, then a colour-enhancing sealer may help.

    It would help me if you could send a picture or two

    Hope this helps


  166. lesley | Aug 22, 2012 | Reply

    Hi there,

    I have a similar problem to Julia above. I actually used a natural acid based anti limescale bathroom cleaner on my kitchen cupboard doors and the drips from the product have left splat marks on my natural slate floor. It looks like it has almost bleached it slightly as they marks are lighter coloured. I tried the solution you suggested for Julia by that has not worked. I wonder can you suggest anything else. I thought of applying some left over sealing product to them as that did take the slate a shade darker?
    Any help would be very much appreciated.
    Thank you in advance

  167. Sam | Aug 22, 2012 | Reply

    Dear Ian,

    My tenants have recently left the slate hearth of my fireplace covered in what are obviously large splodges from using a household clear on it. Is there any way this can be repaired?

    Many thanks for any assitance.

  168. Ian Taylor | Aug 23, 2012 | Reply

    Hi Lesley, it sounds more like you have etched the slate than left deposits, so using more of the cleaner on the slate is not a good idea (assuming this is what you mean about trying the same remedy as Julia).

    Etching removes some of the surface of the stone, not all slate will do this but some will. You cannot get that missing stone back, your idea about using the darkening effect of your sealer may certain help, (the sealer will need topping up on the etches in any case) so well worth a try.

    failing that you may need to get the slate re finished, if the spots are only small, you could try rubbing with some fine emery paper and a little water

    Hope this helps


  169. Ian Taylor | Aug 23, 2012 | Reply

    Hi Sam,

    It depends on whether the marks are stains or etches. If they are stains, then I need to know what they are, but it sounds more like damage (etching) from a potentially acidic cleaner. This might not be repairable – you may need ot get the stone surface refinished.

    If they are oily marks from some kind of polish then you could try an alkaline cleaner.

    Hope this helps

    if you can provide any more information I may be able to help more


  170. Marty | Aug 23, 2012 | Reply

    Hi Ian, I tried to read through all your comments hoping to find a similar situation to mine. I bought an early 50’s mid century modern home with black large different sized smooth slate floors having up to an inch grout based on the odd sizes. It would be gorgeous if it’d been cared for. I seriously doubt anything has ever been done to it other than moped and obviously waxed over the years and as a result is very dull and dirty looking, especially all the edges. Again, I think a build up of ‘old school’ wax and grime over the years. I need a turbo cleaning product hopefully by name if you have any recommendations they are much appreciated.

    The same room has stacked stone pillars and walls floor to ceiling and it looks like wax buildup has been splashed onto those over time also. Could the same cleaner above be used on them also? None of my materials are new, they are all original to the home built in 1951.

  171. Ian Taylor | Aug 23, 2012 | Reply

    Hi Marty,

    I would use my normal procedure of starting with an alkaline cleaner first, if this is not sufficient, try adding a micro abrasive. In some cases a stripper would be required, it all depends on how much build up there is.

    As you are in the USA, try Aqua Mix Heavy Duty Tile & Grout Cleaner in conjunction with nanoscrub or equivalent. You should be able to use the same on the walls too.

    Hope this helps


  172. Chris Eyley | Sep 24, 2012 | Reply

    I have just finished laying a grey/green honed slate floor in the Kitchen.
    After a party at the weekend i now have lots of small white marks all clustered together in certain areas, I dont think it is a spillage, it seems more like stiletto heel marks and the tile does feel like it has indentation, I know its difficult for you to say without seeing but do you think the marks could be polished out with fine wet/dry paper, if i wet the tile the mark does not fully disappear so I think just a liquid polish will not work.

    Any Ideas

  173. Jerry | Sep 25, 2012 | Reply

    I hope that you can answer this question for me. My only shower is out of commission until I find out what to do.

    The shower is finished with 12 x 12 black slate tile. It was looking grey and tired so after trying some spray on tile and grout cleaner with no success I stripped whatever sealer there might have been using Aquamix Sealer & Coating Remover. When I stripped the tile there was no apparent residue. However the lower back wall and adjacent corner of the shower turned a blotchy, very light grey color as if it was very dry.

    Twenty four hours after stripping I began sealing the tile with Aqua Mix Enrich & Seal in the hope that when it was absorbed by the slate the grey would turn black. I sealed most of the shower and it looks great except for the area that I mentioned above. I stopped before sealing the back wall because it was apparent that the grey was not going away in the adjacent corner.

    I have stripped and re-finished quite a bit of this material in our condo in the past but have never run into this problem before.

    What should I do now? If I seal the back wall it will look terrible forever or until I paint it or something. Perhaps some Grecian formula? Should I try stripping this area again? Help!

  174. Ian Taylor | Sep 25, 2012 | Reply

    Hi Chris,

    I think you have partly answered your own question. It does sound like heel marks I have seen this a lot. The darker the slate, the more white the marks appear. basically it is the rough edges of the tiny little crater that was created by the heels that have not had time to soften. Over time (quite quickly) the stark, white edges will rub back to become less notieable (and will eventually look like the do when wet, so still there as actual stone has been removed/scratched/impacted etc) but they will start to blend in. This is akin to the same ting in real wood floors – over time they get pock marked to heck but it is accepted as ‘ageing’ – slate will not suffer quite as badly as the wood.

    you could certainly try a little wet & dry – no harm it might take the edge off the marks a little. If the slate has been sealed, and was sealed with a colour enhancing sealer, try dabbing a tiny bit more sealer on the spots then rubbing the surplus off and buffing with a soft cloth.

    What you cannot do is completely remove the marks, not with out resurfacing the whole floor – and that means grinding which is just not a practical solution.

    Hope this helps


  175. Ian Taylor | Sep 25, 2012 | Reply

    Hi Jerry,

    I think I know what this is.

    Whatever sealer was on before, was a bit thicker than you have experienced to date, or the Stripper was not allowed to dwell for long enough.

    That stripper is a great product, but it needs time to work – up to an hour. What I believe has happened is that for some reason (either the sealer was thicker there or you used a slower dwell time on that section) the stripper has only done half a job.

    It has broken the sealer down, take the surface off it if you like, killing the shine and transparency, turning the remains of the sealer dull, opaque and greyish-white. The solution is simple, re apply more stripper, let it dwell for longer, keep wetting it with more stripper, and scrub hard then rinse really well with a mild soapy solution (this just helps remove all the stripper). Polish it dry with a towel, then let it dry naturally -you are just going back to finish the job it started.

    I have reservations about using Enrich n Seal over stone that has been previous;y sealed, even it is has been well stripped, but if you hare getting good result son the other walls then there is nothing to suggest you wont on this wall, once it is fully stripped.

    Hope this helps


  176. Jerry | Oct 1, 2012 | Reply

    As you suggested it seems that I had not removed all of the old sealer before applying the new Enrich & Seal. I had to go through three circuits of stripping the shower until I was confident that all the sealer, both new and old, was gone. That was truly a hellish experience which I never wish to repeat! The fumes were brutal. I don’t usually bother with a respirator but I sure did on this project. Yesterday I applied the new Enrich & Seal and the black slate tile positively sparkles. That was a hard lesson learned but at least the final result was good.
    Thanks for your help. I really not think that there was any old sealer left and would probably have tried some other, completely wrong approach.

  177. Annette | Oct 15, 2012 | Reply

    Hello, I wonder if you can give me some advice please. We have purchased some old smooth slate slabs recovered from an old school and want to use them as a hearth for our woodburner. The slabs are coated with a varnish finish. Could you advise how best to remove this varnish please? Also we would like to darken the appearance of the slate a little, can you recommend a product to both seal and darken the slate leaving a mid sheen finish? Thankyou for your help. Kind regards, Annette :)

  178. Ian Taylor | Oct 16, 2012 | Reply

    Hi Annette,

    You will need a good paint or varnish remover for that, you could try a sealer stripper but depending on the thickness of the varnish it might take a few goes.

    As for darkening it after, provided you get it completely clean/stripped then you could try an enhancing sealer, like Enhance n Seal by All for Stone

    Hope this helps


  179. Annette | Oct 17, 2012 | Reply

    Thankyou Ian for your advice which is so much appreciated :)

  180. Sue Ewing | Nov 4, 2012 | Reply

    Hi there. Fabulous, useful site – and I wish I’d read it a few days ago!
    I’ve just had some beautiful multiple- coloured slates laid in my hearth. They’re not smooth. The stove installer is coming tomorrow and I told him I’d seal the slates myself this weekend before he comes. I had an unopened bottle of Plasplug Tile Sealer (suitable for slate, stone etc), bought years ago. I’ve given the slates three coats, following instructions to the letter. They look fine, but I was hoping for a soft sheen, to bring the colours out more. This hasn’t happened and the slates still look matt. On the bottle, it recommends using Plasplugs Marble & Slate Clean & Shine but it’s no longer available. So, my question is… Can you please advise what I should use to give the desired sheen to the slates?
    Thank you very much for your help.

  181. Ian Taylor | Nov 6, 2012 | Reply

    Hi Sue, you really needed a coating sealer, there are several on the market, but they may not work now as they need some porosity to bond. That porosity will now be greatly reduced due to the impregnating sealer you have used so you may need to strip that out first

    Hope this helps

  182. Sue Ewing | Nov 8, 2012 | Reply

    Thanks very much for your help. I have given it a coat of Lithofin Slate-Seal and it seems to have done the trick – the hearth now has a lovely soft sheen. Thankfully there was no need to strip out the sealer! Thanks again.

  183. lee | Nov 8, 2012 | Reply

    Hi there,

    I tiled a kitchen floor, (8m2) 6 weeks ago using black slate tiles 300×300. Done the usual as ive tiled dozens of slate floors over the years. Once tiled, ive thoroughly cleaned tiles before grouting. Grout washed off, and tiles left to dry overnight. So next day, i sealed the floor, and to enhance the ‘black’.

    I returned next day, to see that the slate floor, was looking good, apart from a dozen tiles that werent so ‘dark’ or ‘black’ as the majority. So i thought maybe seal these ones again.

    However a few days later, these dozen or so tiles, look awful. They look cloudy grey/whitesh colour. The affected tiles are dotted around the floor, not just one area. Where as the good tiles, look jet black. Why the difference ?….they all been treated the same.

    Im at a loss, to why this has happened. Ive ask several other tilers, and been to tile shops for advice, but nothing… answer.



  184. Robert heath | Nov 10, 2012 | Reply

    Hi Ian, just looking for some advice on cleaning a slate floor. I laid a square tiled grey slate floor, uniform in colour throughout, with an uneven surface to it, in our kitchen and dining area about six years ago. At the time, I only gave it one coat of sealer, and over time the floor has started to look a bit dull and dirty and regular mopping just doesn,t seem to do much. The grout as well is also looking pretty dirty and stained. I was wondering what product you would recommend that could give it a proper clean, maybe take away the weathered seal and just generally a really good clean, and also any tips for doing this. Also what new sealant would you recommend putting on when finished cleaning. Would appreciate any help you can offer. Thanks, Robert

  185. Ian Taylor | Nov 13, 2012 | Reply

    Hi Lee, first of all you don’t say what type of sealer you have used; was it a coating sealer or an impregnating sealer? If impregnating, was it a natural one or a sealer designed to enhance the colours?. The kind of issues you are describing suggest a couple of possibilities.

    First of all, if the sealer has darkened the tiles then it sounds like you used either a topical coating or an enhancing impregnating sealer. One reason some tiles go dark and not others (esp with the latter) is if there had been any other sealer present before, thus stopping the sealer from getting in and doing it’s job. However as this was a new floor I do not think this as likely.

    The other issue, and it can be a big issue with enhancing sealers and topical sealers, is too much moisture before sealing. I note you say you left it over night, frankly this could be your problem. many sealers of this type will need the floor to be almost completely dry – overnight is often no where near enough – even if the floor ‘looks’ dry and even if you have done hundreds like this and never had a problem (that is more by good luck than good judgement I am afraid). If there was sufficient moisture left in the floor (and it could have been in the grout joints) then these type of sealers can take in some of that surplus moisture and it permanently affects the way they cure. This can get worse over a few days as it finishes curing, so more tiles can be affected on day two than on day one etc.

    I cannot be certain, but I am leaning towards too much moisture as your explanation,. I suggest you get onto the tech department of which ever sealer you used for a recommended solution – If I am right, the sooner you react the better, unfortunately I was away over the weekend and did not see this until now.

    Hope this helps


  186. Ian Taylor | Nov 13, 2012 | Reply

    A few questions there Robert. First of all, it sounds like the floor is ready for a deep clean, with something like Xtreme Clean by All for Stone – a high alkaline. Given what is left of your existing sealer, this may well all come off with the deep clean. f not, you may have to use a sealer stripper.

    AS far as re sealing there are lots of choices available, you may not get the opportunity to use an enhancing sealer though as the floor has been sealed before and this presents a bit of a risk that you wont get even coverage and penetration, resulting in a patchy appearance.

    You could go for a coating sealer, given you have a textured finish, I would guess you had something similar before, the are easy to apply and can last a year or so before they dull down and need replacing.

    Hope this helps


  187. Amie | Nov 19, 2012 | Reply

    Hi Ian,
    I’ve had a browse through all of he posts and you certainly seem to know your stuff but I couldn’t quite find an answer to my tile problem!

    In my en-suite both the walls and floor are covered in what I believe to be slate tiles. They are matt, slightly contoured and a beige / sand colour. I have been cleaning them with floor wipes such as Dettol (not sure if the chemicals in these are the problem) and they now have dark grey spots all over them – it looks a bit like stars in a night sky, however it has only happened on the floor, the walls are absolutely fine even though I’ve used a bathroom cleaner on them.

    I would like to find a way to remove the marks if possible, any help would be greatly appreciated. Was going to send a picture but being a bit blonde and couldn’t see where to attach!

    Many thanks,

  188. Nuala | Nov 24, 2012 | Reply

    Hi, I have just had slate kitchen floor tiles fitted, I have two problems the first is that I haven’t been able to seal the floor as cannot remove the grout residue and the second is that my delightful children spilt apple juice and didn’t tell me until it had left an almighty stain – how do I remove both to prepare for sealing? Thanks in advance nx

  189. Ian Taylor | Nov 26, 2012 | Reply

    Hi Nuala,

    OK, the grout residue that is caught in the ridges, generally needs a mild (SAFE acidic cleaner – DO NOT USE one based on hydrochloric acid – this means most brick acids. Look for one that claims to be based on phosphoric acid. Use in accordance with the instructions, but basically pre-wet the floor.apply the dilute cleaner, leave it for a few minutes, then scrub with a nylon scrubbing brush, an old tooth brush, or something that can get into the texture. Rinse well and repeat – it may take several goes to get through it safely, without doing damage to the grout in the joints).

    You may find that some of the apple juice stains come out as a result of the above but if not, you will need to switch to an alkaline cleaner such as All for Stone Xtreme Clean. Or even a poultice.

    Hope this helps


  190. louise | Nov 29, 2012 | Reply


    I have just had a pale grey and rust slate hearth fitted, the fitter has oiled it and now it is black. Will it dry to the original colour?



  191. Ian Taylor | Dec 5, 2012 | Reply

    Hi Louise,

    I think it depends on the oil but, quite possibly no. If it was going to return to its original colour I think it would have done so by now.

    The oil is acting like a colour enhancing sealer it is leaving behind some solids that affect the way light is reflecting back from the slate, the same thing happens with water, but of course water evaporates out and leaves it as it was, so when dry the colour goes back to how it was.

    Unlike an enhancing sealer though, a good alkaline/degreaser should be able to remove it, you could then use a clear, water-based sealer to seal the slate if needed and this should not alter the colour

    Hope this helps


  192. Nuala | Dec 16, 2012 | Reply

    Hi Ian thanks so much for the help, think I may have been too late tho as even after cleaning with heavy duty cleaner I sealed it and now it looks awful :0( I obviously did something wrong as have permanent water marks and general dullness over the tiles – I may have to start again – could you please recommend something to remove the sealant I put down (i used diall from local DIY shop) and then a cleaner and sealer that will do the job – thanks so much Nuala x

  193. Ian Taylor | Dec 17, 2012 | Reply

    Hi Nuala,

    did you clean the grout residue off with an acidic cleaner as per my suggestion, as you only refer to an alkaline one? – did you do this before sealing.

    You can use a stripper to remove the sealer – might be best to call the company who’s sealer you used for their recommendation for a stripper.

    if you get the sealer off, then you may still need to do a acid clean, as per my original advice, to remove any grout residue.

    Regarding the water marks, any chance you can email me some pics?

    hope this helps


  194. Jennifer | Dec 22, 2012 | Reply

    Hi Ian,

    I have some kind of black slate or sandstone(??)hearth at the base of my decorative gas fireplace. I foolishly tried to clean pet urine off of it with vinegar, and now I’m afraid I may have etched it as it has a greyish white area where the vinegar was. Either that or I stripped the sealant? Can you please tell me how to tell for sure what I am dealing with and how to possibly repair the etch myself or reseal it? When I wipe with water, it restores the black color until it dries again, so perhaps there is hope? I can send a photo if that helps, but I don’t know where to send it. Thanks so much!


  195. Elizabeth | Dec 22, 2012 | Reply

    Hi Ian,
    We have just acquired a home that has a 1000 sq. ft. room that is entirely floored in slate. I don’t think it was ever sealed, as it appears dull. The former occupants evidently allowed dogs to live in the room, and there is an HORRIFIC odor (dog excrement and just plain dog smell). I have tried scrubbing with white vinegar, spic n span, pine sol, and plain soap and water to no avail. Every time I scrub, the smell gets stronger. Is there anything at all I can do to remove the odor? I think because it appears unsealed, the odor is deep into the porous slate. Thank you so much!

  196. Lesley | Dec 22, 2012 | Reply

    Hi, my daughter sprayed anti bacterial cleaner on our black tectured slate fireplace. As soon as i noticed i washed it with water but the slate has white streaks that i cant remove. Any advice would be appreciated.

  197. Ian Taylor | Jan 2, 2013 | Reply

    Hi Jennifer,

    If it is black, I would be more inclined to believe it is slate (although it could be other similar stones like mudstones/silt stones etc)

    It does sound more like etching to me than removal of sealant, although if you had an impregnating (below surface) sealer, then some sealer may have been removed at the same time. Had you a coating sealer (visible low sheen or glossy coating) then I doubt you would have removed it with vinegar, and you would not have an etch either.

    The problem temporarily disappears with wetting as the water evens out the surface (which was made rougher by etching) and gives a flat, reflective surface (more like the flatter, smoother surface that existed before etching), as the water evaporates however, the effect fades and the etch mark appears to return.

    If it is etching, then you may be able to use an enhancing sealer to do the same thing that water does, but permanently. However, it may darken that part of the slate more than the rest, if there is still a good amount of old sealer in the rest of the stone, then this may look odd (the enhancer will not get into the stone over the other sealer, only in the etched part).

    If you slate surface was polished, or very finely honed, then the etch may also be quite rough to the touch, by compassion, if this is the case then you might be better having the surface re-finished, perhaps by a local stone professional. You could perhaps try yourselves with diamond hand pads – I don’t have time to go into that here but you may need several grades and you would have to do the whole surface, and re seal afterwards

    I hope this has been of some help, you can send me pictures – use the contact us page on the blog to send me a message and I will reply, you can then send me some pics back to that email


  198. Ian Taylor | Jan 2, 2013 | Reply

    Hi Elizabeth,

    I think you have got it about right, I am no chemist but I think there is a ‘reservoir’ of the time-absorbed contaminants and you are bringing it out bit by bit, also re wetting the dry contaminant may be reactivating it, and allowing the odours to come to the fore.

    Logic says that eventually this will diminish and stop – the reservoir of contamination will be finite.

    Having said that i don’t think anything acid based (your vinegar) is going to help, these contaminants are best treated with a high alkaline cleaner, there are many on the market, especially in your part of the world.

    I suggest you conduct a deep clean with a high alkaline cleaner, follow on bottle instructions but essentially:

    1. pre wet the floor
    2. apply the cleaner
    3. leave it to dwell for 15 minutes DO NOT ALLOW IT TO DRY OUT – keep adding more if it does
    4. scrub the floor, and particularly the grout joints
    5. remove the dirty cleaning solutiojn – preferably with a wet vac if you can get one, if not with a mop
    6. rinse well – this means CLEAN water, applied to the floor, SCRUBBED a little with a CLEAN mop, then extracted again
    7. RINSE again – repeat step 6 to be double sure – also makes sure there is no detergent left to build up

    allow to dry, ventilate the rooms and see what the smell is like after that – try to be subjective – is the smell gone, still there but not as bad (in which case repeat all of the above – because it is working) or is it worse – in which case repeat the above because it is working – it is bringing the bad stuff out and to the top

    this may take several attempts, but the above process is by far the most efficient –

    if the odour is really bad, you may have to consider using bleach for one of the cleans, then rinse and clean as described as above

    once you are happy you can find a suitable sealer

    Hope this helps


  199. Ian Taylor | Jan 2, 2013 | Reply

    Hi Lesley,

    Difficult to know exactly what has happened here, but it could be that there was some kind of sealer/coating or polish on the slate and that the cleaner has partially damaged/removed the coating – so the streaks could be ‘clean’ spots – or where the alkaline or solvent in the cleaner has partially dissolved the coating and then left a concentration of the now damaged coating in streaks

    Or it could be a deposit (soap, oily, waxy etc) from the detergent itself.

    Try some hot water with w neutral cleaner (like a few drops of washing up liquid) and rinse well afterwards

    Also you could try some solvent – a good one is acetone and the easiest way to try this is just take some clear old fashioned nail varnish remover, dab a bit on onto the streaks, and rub. let it dry and see if it has A) removed the streaks and nothing else, B) removed the streaks and something else – maybe coating, made the slate look dull, or C) – does nothing

    Try this and come back to me

    Hope this helps


  200. Lesley | Jan 8, 2013 | Reply

    Thanks ian i will have a go as advised.

  201. Lisa | Jan 13, 2013 | Reply

    I recently removed small rugs from my slate floor and noticed that the non-skid pad under the rug is stick to the floor. I fear that even though I waited a couple of days to put rugs down after sealing it (about eight years ago) I may have put it down too soon. I have removed most of it with a light scrubber. But there is still something there that I can actually scrape off with my fingernail. Obviously I can’t do that to two 5×7 foot spaces. Any ideas on a product that might help? Thank you. It’s is a great website! Very helpful.

  202. Lori | Jan 14, 2013 | Reply

    I have black slate on the hearth of my fireplace. My toddler left a sippy cup of milk on its side on the slate. There is now a white stain on the slate. It turns back to original color when I wipe it with a wet cloth but the stain comes back when it dries. Any suggestions on getting it out?

  203. Samantha | Jan 17, 2013 | Reply

    I have read through these post an I don’t think this question has been asked, but apologise if I am doubling up. We have recently moved into a house with slate floors (dark brown with an uneven textured finish). The previous owners had a rug down along the breakfast bar the prevent scratching the floor with the bar stools, however I don’t think it has even been lifted up to vacuum or mop under and now the rug is well and truly stuck to the floor with what i assume to be the build up of grime, spilt drinks etc that has probably occurred over the years. Any suggestions on removing the rug easily without damaging the floor or putting my back out from trying to rip it up?

    Thank you in advance for any suggestions.

  204. Ian Taylor | Jan 18, 2013 | Reply

    Hi Samantha,

    I think you are going to have to carefully start to roll back the rug, and have a new, sharp, wide bladed scraper to hand to try to free the backing, it will be a bit like shearing sheep if you can imagine what I mean, and will inevitably leave bits of the backing on the floor and the occasional metal mark form the scraper (you may be able to find a hard plastic scraper which might be better)

    once the rug is up, I would suggest a mixture of a high alkaline cleaner and an abrasive cream cleaner to deep clean the floor and remove the traces of backing – then rinse the floor and assess it’s sealing requirements

    Hope this helps


  205. Ian Taylor | Jan 18, 2013 | Reply

    I would try an alkaline cleaner, and maybe a cream cleaner with a small amount of abrasive it=n it first – if it is a residue of calcium from the milk, something mildly acidic might help.

    Milk contains both lactic acid, and calcium, as well as oils and fats so it is hard to know for sure exactly what is causing the issue, hence a little bit of experimentation – a cream cleaner is very mild and you are relying on the abrasives within to gently rub off the stain. In the USA you can get a product called Nanoscrub.

    Hope this helps


  206. Ian Taylor | Jan 18, 2013 | Reply

    Hi Lisa,

    You could try a micro Abrasive cleaner like nanoscrub or similar. Failing that you may need a solvent sealer stripper, this will obviously affect the sealer so will need to re seal after

    Hope this helps


  207. Samantha | Jan 18, 2013 | Reply

    Thanks Ian for the advice and quick response, we will try that, hopefully we can get it up without to much damage to the floor.

  208. Natasha | Jan 18, 2013 | Reply

    Hi Ian

    Started reading through your posts and then realised how many there were so thought I would email directly, as you seem to be very good at responding and certainly know your stuff.

    We live in Wales and have an old, derelict cottage on our land. We have used some of the floor slates from this cottage to lay a floor in our kitchen. The slates are big – most of them at least two foot long by at least 14″ wide. They are nearly all at least 2″ thick. The cottage, and therefore we presume the slates, is about 150 yrs old.

    They have been laid on lime, with tight gaps between them which have been grouted. The slates were just brushed down before we laid them – so they were anything but pristine to start with. As we have been working on the kitchen (for what is probably a good year) they have collected plenty of general dirt, dust and the odd splatter of plaster, the big chunks of which we have managed to get off. They are currently a dusty unpleasant grey/brown colour. They are quite uneven in their general appearance – lots of dips and undulations.

    THe building work as all but finished now and we are at the point where we want to clean the floor up properly and maintain and care for it correctly. Obviously when I wipe the floor with a wet cloth, the blackness of the slate comes up lovely, and then disappears. I really have no idea what to do to get this really clean, seal and protect it and care for it in the longterm.

    Please could you help with suggestions and names of products etc? We would like to keep things as natural as possible, but realise that, at least during the initial clean up, we might have to use something stronger.

    Many thanks

  209. Ian Taylor | Jan 21, 2013 | Reply

    Hi Natasha,

    OK, well you have very old, riven slate slabs, and they are probably fantastic.

    Fixing them on lime may create issues – Do you mean a lime mortar? I am guessing this was because for some reason, in the old building, a proper concrete floor was not possible?

    There are a couple of points, one is that if you have no concrete, you are also not likely to have a properly installed damp proof membrane (I am making assumptions here). This in itself may not be an issue, as for years, in traditional housing like this, it was the highly moisture-resistant nature of the Welsh Slate that led to it being used as flooring (and of course for its durability, aesthetic qualities, and its plentiful supply) It was the slate itself that created the damp-proof layer.

    So I do not see you having too many issues with damp etc, however, the tight joints and will have been hard to grout fully, there will also be inherent movement on the lime mortar so there will be fine cracks between the slates. This means that when you wash the floor – water can get down into the lime mortar – if this happens, then when the floor dries out after cleaning, it could kick start some efflorescence – growth of white crystalline deposits, coming up through the grout joints.

    If you feel the joints are well sealed with grout then you may be ok.

    After building work like this it is typical to use a mild acidic cleaner, one based on a mild acid like phosphoric as much of the dirt will be mineral based (cement, plaster, building dirt etc) and this type of cleaner should not harm the slate – but do a test first of course!) Do NOT use a brick acid, or one based on HCL. Once this has been done, and the floor rinsed and dried, you may now see other things on the slates such as old layers of polish and general, ingrained dirt and grime. At this point you could switch to an alkaline deep cleaner, and use it with a micro abrasive cleaner like Microscrub.

    Just make sure you manage the water and get it picked up – do not leave it to linger too long.

    For the acid wash:

    1. Pre dampen the surface with a wrung out mop
    2. apply diluted acid cleaner (see bottle) with mop to a workable area – say a couple of square metres at a time. Leave it on for about 2 minutes
    3. now scrub – preferably with a rotary scrubbing machine with a medium hard nylon brush head – if doing by hand then it is best with an old fashioned nylon scrubbing brush (deck brush)
    4. Pick up the dirty solution with a wet vac if you can – other wise it is a lot of mopping, chancing water and rinsing – you can hire a reasonable wet vac at any tool hire store – it will save you hours of work.
    5. Rinse out your mop, put fresh water in the bucket and mop the floor again – this is to rinse the floor
    6. Wet vac again
    7. Rub the floor dry with an old towel.
    8. Do not skip any of the above points!

    when dry, you may have to do this again, the downside of using a mild, safer acid is that it works on thin films then is spent, but this is the safe way to work, taking little bits at a time. limit the time you expose the floor to water by picking it up and drying it as mentioned above. If you need to do an alkaline clean after, then you will need to use more water, for longer, but that is not really avoidable.

    Let it dry out for at least a coupe of days, preferably a week (give time for any moisture to out of the the lime mortar bed.

    See if you have any whitening at the joints – if so, a quick wipe with some more dilute acid cleaner, rinse and rub dry immediately may sort this – then wait again, until you are happy you don’t have a re-occurring efflorescence issue).

    Sealing is another question, after cleaning your slate may have a rather subdued and dull or lifeless appearance. If you like the deep black of the slate when it is wet then you have two choices, a coating sealer (that will last a limited time say, 6 months to 3 years) or a colour enhancing sealer that will last a lot longer.

    There are issues with both, topical is easy to apply, looks shiny, or at least has a low sheen, so looks clean and also helps cleaning as the surface will be easier to wipe down. However if you don’t like the sheen, (some feel it looks artificial) then you may not want this, also it is on top of the slate, not within it so it will wear and be subject to attack from your cleaners.

    The enhancing sealer (such as All for Stone Enhance n Seal) will bring out the colour, without the shine, but the floor must be bone dry, including making sure there is no latent moisture in the lime mortar. Also this would be a permanent solution, there is not taking it back out if you don’t like it.

    Hope this has helped


  210. Ann | Jan 25, 2013 | Reply

    I have a black slate floor in my kitchen…recently i cleaned it with Cif floor cleaner and it has left a white bloom residue on some of the slates…the rougher ones.
    Please have you have a method of cleaning i can use to remove it !

  211. Natasha | Jan 26, 2013 | Reply

    Hi Ian

    Thanks for such an informative reply and apologies for the delay in replying. You are correct that in that we used lime mortar – there is concrete and a damproof course underneath though. WE used lime in case we ever wanted to get the slates up again – it would cause less damage to the slate than using concrete. And you’re right too about them being fantastic!!

    We don’t have any damp problems and the gaps, although quite narrow are well grouted.

    Will follow your instructions – I;m sure they will come up lovely!
    THank you again for going into so much detail – I really had no idea where to start with all this.

    Best wishes

  212. Ian Taylor | Jan 29, 2013 | Reply

    Hi Anne,

    OK, it could just be a residue of the cleaner – try wetting the floor and adding a tiny bit more CIF – to ‘clean it self’ by re-wetting it, with more of itself, you may find you can break it down and wipe away – if you can, immediately after (before it dries again) rinse with clean water and a clean cloth.

    If this does not work, then maybe you have partially removed what was left of a coating sealer – Imagine having finely painted nails (no, I don’t know what this is like, but I have daughters!) and you inadvertently rub one of them with an emery board – it takes some of the coating, (the varnish) off, and maybe the varnish starts to look a bit ragged, and even white at the edges, so the only option now is to completely remove the rest of the varnish (from that nail at least) and start again.

    As Cif is an abrasive, it may be just enough to damage, or scuff the coating sealer on the slate, but not enough to fully remove it – so consequently you can now see damaged sealer made opaque by the Cif, that you were not aware was even there – in which case, you may have to get a sealer stripper to remove it, then re seal

    Hopefully it is the first one

    best of luck


  213. Ian Taylor | Jan 29, 2013 | Reply

    Your welcome Natasha

  214. Sue Morris | Jan 31, 2013 | Reply

    Hello Ian, Apologies if this query has already been asked/answered; your advice would be very welcome. I have Chinese black slate tiles on my kitchen floor which I laid over 10 years ago and sealed with Lithofin Slate Seal. In preparation for reapplying this product to reproduce the lovely shine the floor had originally, I’ve steam cleaned the tiles using my wallpaper stripper “pad”, after spraying the tiles lightly with a degreaser, scrubbing with a nylon abrasive pad, rinsing with clean cold water and allowing to dry naturally. There are places where a white bloom or efflorescence has appeared, some of which seem to reflect the shape of the wallpaper pad (straight/rectangular shape). Am I able to remove these marks and if so, with what? I suspect that if I reapply the sealant without removing the white marks they will still show up. Thank you in anticipation of your response.

  215. Liz | Jan 31, 2013 | Reply

    Our slate shower has developed a whiteish/grey speckle over the tile. We seal it yearly but we believe water has gotten in behind the seal (maybe through the grout – who knows).

    How can I fix this problem? Do I need to remove the seal, scrub and reapply. The local tile shop suggested I usse sugar soap but that sounds a bit wrong to me.

    Thanks for any help you can offer

  216. Ian Taylor | Feb 1, 2013 | Reply

    Hi Sue,

    I suspect it is not an efflorescence bloom (especially on slate, it would most likely show up first in the joints). The steam pad shaped mark is the clue – I think what you have done is partially stripped what was left of the slate seal – breaking it down where yo have let the pad linger, and so destroying its structure and integrity – making it opaque in the process.

    So I would try a stripper on those marks (to see if you can complete the stripping that the steam cleaner started). One little tip you can try is to dab some nail varnish remover (the old acetone type) with a cotton wool pad and see if that removes any thing. If it does then great, it is telling you that a solvent type sealer stripper would do the job.

    If so then you will need to consider stripping the floor completely, before reapplying any sealer.

    Hope this helps


  217. Ian Taylor | Feb 1, 2013 | Reply

    Hi Sugar soap is basically an alkaline cleaner – it may do little here (wont do much harm either apart form degrading your sealer – but you may have to remove that anyway).

    It sounds more like hard water deposits/soap-scum etc to me – if so it might be a deposit on top of the sealer. I would try something very mildly acidic first – a proprietary cleaner based on citric, sulfamic or phosphoric acid (or similar) – nothing strong though – so no Muriatic (HCL).

    you may find that it just come s right off with a mild acid wash.

    Hope this helps


  218. Sue Morris | Feb 1, 2013 | Reply

    Thanks for the advice Ian. I’ll try the acetone route first. As it happens, I have a quantity of acetone from ex-nail salon use in my garage! Can you recommend a solvent type sealer stripper should I need this? Thank you again. Sue

  219. Blair | Feb 3, 2013 | Reply

    Hi Ian,

    Really great blog.

    I have a different query about a slate fire surround. I live in an 1880 built flat in Edinburgh and my fire surround is made up of what appear to be matt black stone. It has very flat and smooth finish but there are a couple of areas of the black missing, exposing a slate textured grey surface, so it seems like it is coated with something. I guess the coating was for decorative (maybe make it appear like marble or something?) and protective purposes. The black colour is quite dominant in the room and ideally I’d remove the coating to expose the natural stone below, to soften the appearance. I’ve tried acetone and nitromers paint stripper without any success. I’ve tried scraping a little and the stuff does come off but it is quite adherent and doesn’t chip off, more scrapes off. I don’t want to scrape it all for fear of damaging the base stone.

    Have you come across this before? Is it a particular coating? Any suggestions in how to remove it? Reading through your blog for tips, it seems like an abrasive grind/polish might be needed?

    Any suggestions would be appreciated.



  220. Ian Taylor | Feb 4, 2013 | Reply

    Hi Sue there are various ones out there but yo can try a paint stripper white spirits or a proprietary sealer stripper

    hope this helps


  221. Ian Taylor | Feb 4, 2013 | Reply

    Hi Blair,

    It could be anything, people have put all sorts on slate over the years, oils, linseed, poly-urethane coatings, varnishes etc.

    You have tried the obvious things.

    You know, without seeing it, it is not easy to advise but it could be that there is no actual coating, just that the surface has been mechanically polished – this would make the naturally riven slate surface, flat and smooth and allow the darker colour to come through. The patches of the lighter colour could be where that polished surface has been damaged/chipped etc.

    Either way you may have to resort to removing the ‘polish’ by mechanical means –

    You will not get back to a natural ‘riven’ finish as that is the finish that occurs when slate is split (by a skilled craftsperson) along its natural cleavage plane. But you could use coarse grits or honing powders to take the polish back to unpolished or a honed finish (honed is flat and smooth, but not necessarily reflective, so not like polish, the dark colour will be less intense) .

    This is not always easy to do in situ and if you can take the surround down and take it to a stone professional , it would be easier to do on a bench. If that is not possible then hand held polishing machines would be needed with a pad head that can apply honing powders, A honing powder of grit 500 or 400 or below should remove the ‘high polish’ (the small the number number, the coarser the grit – so 400 grit is not as fine as 500 etc)

    Hope this helps


  222. Ashley | Mar 17, 2013 | Reply

    Hi Ian,

    My grandmother has a stain on her slate tile floor that was created from a cow hide rug. It is whitish and spotty. Do you know how we could remove this?


  223. Ian Taylor | Mar 18, 2013 | Reply

    Hi Ashley,

    I am not sure if it is something that has been deposited by the cow hide (some fats, tanins or other material leaching out from it?) or if it is just that the hide, in covering the floor, blocked the stone’s natural tendency to ‘breathe’ If there is any moisture beneath the stone that has been trapped by the hide then it could be efflorescence – soluble salts being left there.

    Or it could be that it is some kind of mildew/mould etc.

    Try just wiping over some of the white spots, with a damp cloth. If they disappear immediately, but come back as soon as the floor is dry, then this might indicate efflorescence, if so a mild (and suitable) acid based cleaner, used very dilute may be all that is required – so you could try this, but make sure that A) – your slate is not acid sensitive (most are ok, but some of the more colourful ones can dull a little bit) and B) that you do not use a brick acid, based on HCL –

    failing that, try a good high quality alkaline deep cleaner and a scrubbing brush.

    If this does not work, try a solvent stripper type product

    Let me know how you get on

    Hope this helps


  224. Chris | Mar 27, 2013 | Reply

    Hi Ian,
    Wondered if you could help- we have a slate hearth (not sealed) and someone has cleaned the ash with a baby wet wipe which contains some bleach. This has left white marks along the edges of the tiles- can I restore them to their original colour/ will they be permanently glossy if I do so?
    Many thanks,

  225. Ian Taylor | Mar 28, 2013 | Reply

    Hi Chris,

    First of all, baby wet wipes that contain bleach? – Not sure I would want to wipe my baby with such a product??

    OK, you say the slate has not been sealed, but perhaps it has had some treatment (slate oil, some kind of polish, particularly one that contains some kind of colour that will darken the slate a little)?

    I am not convinced that this is a bleaching issue but lets look at what bleach might do and what it should not do: First of all, I doubt very much if even household bleach from a bottle, would really damage a good slate, if the slate is dark grey or black, or green it ought to be a pretty tough material, very old geologically and NOT usually containing any colours or pigments that are mobile, or able to be bleached out.

    However if there had been some kind of treatment, like a colour enhancing slate oil or similar, then the bleach may well have had some effect on that, given what I would hope to be very small concentrations of bleach in the wipes, the effect would be minimal. If this were the case then you may need to clean the slate again, to remove all of the treatment, (so use an alkaline cleaner or solvent stripper) then re treat afterwards.

    My gut feeling is that it is more likely to be a residual deposit from the wet wipes: Whether they contain bleach or not, they will contain lots of things, and unless you rinsed the slate with fresh water after using them, the wipes may well have left some solids or residues. As the slate is likely to be fairly impervious, the moisture will naturally collect at the edges, and at the grout joints which will retain moisture for longer as they are more porous – this seems consistent wit you saying the white marks are at the edges.

    I am sorry I cannot be more precise, do you have any photos you could send me? It might help.

    Things you could try:

    You could try using a high alkaline cleaner and a scrubbing brush, or scrub pad – rinse after and buff dry

    Use some acetone (clear nail varnish remover) – just rub a little on some slate witha cotton pad and see if you get any colour transferring – this will indicate that there is something in the slate (oil or otherwise)

    If you know without any doubt that the slate is untreated in any way, then I really think we are dealing with a dried on residue from the wipes, which means it ought to be removable, it is just case of trial and error to find the most appropriate method/product.

    One other thing that may be worth a try is to use a micro-abrasive cleaner like Microscrub, mildly alkaline and using abrasives derived from calcite, it is soft enough to not damage the stone, but it may help shift stubborn stains

    hope this helps


  226. Bill | Jun 12, 2013 | Reply

    Any suggestions, please.The stove installers sprayed our untreated, light grey slate hearth (made from an old billiard table) with WD-40. They said it would dry back to grey when we protested. It hasn’t and looks like a lump of black ceramic tile which is not what we want. Can anything be done to remove the WD-40?

  227. Ian Taylor | Jun 13, 2013 | Reply

    Hi Bill,

    OK, I have not tried to remove WD – 40 but it is an oil. If it was just one spot or two then a poultice may be useful but as it is all over you are going to need to use some kind of liquid. First thing I would try is a high alkaline cleaner such as Xtreme Clean by All for Stone.

    If this does not do it then you will have to use a stripper (solvent) the slate from snooker/pool tables is often Welsh as it can me made with a very flat surface. If yous is this material, then it is very dense, and with a bit of luck the oil will not have penetrated too deep.

    One quick test you can do, is this: if you can get your hands on some clear, old-fashioned nail varnish remover (the type that contains acetone) – try dabbing a little onto a cotton pad and rubbing a small test spot. If it comes off and leaves the slate, back to its natural light grey colour (and also removes any trace of artificial shine) then this is showing you the oil is removable, I would not suggest doing the whole thing with nail varnish remover, but it does act as a good tester.

    If it comes off easy with the nail varnish remover, then you could try a paint thinner/stripper from a hardware store, but you might still try an alkaline cleaner first – the reason is some solvents, due their oily nature, can in some cases also leave a slightly darkened finish

    Hope this helps


  228. Jintydavies | Jul 23, 2013 | Reply

    I have a metal plant container on my outside brazilian slate terrace and it has been leaching rust for the last two years. I did seal the slate when it was laid with lithofin, but haven’t resealed for about two years.
    I have been hunting around the web for a solution, but yesterday decided to try my favourite product Astonish mult-use cleaning paste, which is gentle enough to use on enamel. I used one of those sponges with an abrasive side on it. Guess what! It came off!
    I hope it works for you.

  229. Ian Taylor | Jul 23, 2013 | Reply

    Thanks for sharing that Jano, yes that product can sometimes work, along with the nylon scrubbing sponge. Provided the rust is just a deposit on top of the stone and it has not had a chance to get too deep into the surface. Like Microscrub, your product contains fine abrasives that can get into the texture of the stone without damaging it.



  230. Raj | Jul 23, 2013 | Reply

    Hi Ian,

    Great site and I hope you can help. I have black floor tiles in my kitchen and think they are slate, I am not sure is they have been treated in anyway but believed that they are. My wife tried to get rid of some staines by using Flash bleach and left the cleaning product to soak into the stain. As you guess this has now left large spots of white staines on the black flooring where she has sprayed and left the bleach. Please could you help and tell us how we could restore the tiles and remove the bleach stain.

    Many thanks


  231. Ian Taylor | Jul 24, 2013 | Reply

    Hi Raj,

    This could be a number of things, first of all, if your slate had been treated, especially with a kind of coating sealer (this may have left a slight sheen) then the bleach will have partially broken this down, so, in this case, the white marks are the remains of damaged sealer. The only answer here is to break down and remove the rest of the sealer. If you can find out what sealer was used, and get some more, you may be able to get away with just removing it from the tiles where the damage has occurred, (but make sure to strip the whole tile, edge to edge), then when rinsed and dry, just re apply the sealer to these tiles. If not you may have to strip the whole floor.

    You could try adding some of the bleach to water, and leaving on a whole tile (where there is already a stain) for a few minutes) then scrubbing all over the the tile with a nylon sponge scrubber or scrubbing brush, rinse and let dry- this may help you blend out the stain.

    Failing that use a reputable sealer stripper.

    It could also be residue of the bleach, a good clean with an alkaline cleaner, or a little more dilute bleach, and a scrubbing brush may resolve this, just do not leave it to soak and also dry in, leave it just a few minutes, keep it wet, then scrub, remove, rinse with fresh water then dry.

    I have seen, in a few rare circumstances, some slates that are let’s say a bit cheaper, or supplied from less trustworty sources, which have been artificially darkened or coloured. IF this were the case the the bleach may have removed some of the artificial colouring to reveal a much lighter ‘real’ colour. However I am guessing that a part stripped sealer or residue is more likely

    Hope this helps


  232. Elailne | Jul 25, 2013 | Reply

    A slate floor was put down in my bathroom but the wrong sealer was used. I wanted an enhancer put down but an impregnator was put down instead. Miracle 511. I’m assuming the Miracle sealer and enhancer I originally wanted to use will no longer work. Any suggestions as to how to get the impregnator sealer off? Some say vinegar, others say no.

  233. Ian Taylor | Jul 25, 2013 | Reply

    Hi Elaine, you will need a sealer stripper, you could contact Miracle’s tech services department and ask their advice. Some of the enhancing sealers on the market cannot be guaranteed to work 100% even after stripping, as it is not always possible to remove 100% of the original sealer, to the point where the enhancing sealer can get in and work

    Hope this helps


  234. Kevin biss | Oct 1, 2013 | Reply

    Hello,I have reclaimed about 25sq mtrs of delabole
    Slate from a site.Want to use it for my c16th cent
    Cottage floor.The slate came originaly from an c18th house.
    It is currently covered in moss and brown dirt.Tried scrubbing
    With jays fluid and stiff brush,it does gradually remove the dirt,
    However it would take me about 6 months to clean.Any ideas (these are large meter sq slates.

    P.s great site.


  235. Ian Taylor | Oct 4, 2013 | Reply

    Hi Kevin,

    OK, the Jays fluid is good at killing algae etc but you may need something a little stronger as a cleaner (but not a disinfectant) to do deep cleaning. Or you may need to do a combination clean.

    I have had success with similar things in the past using a high alkaline cleaner like Xtreme Clean in combination with Microscrub.

    Pre wet the slabs, then apply some of the alkaline cleaner (diluted) leave it to dwell for a good 10 minutes
    then add a small amount of microscrub, and scrub using a scrubbing brush.

    It might take several attempts.
    Rinse well after each wash, you can also then try using a little watered down house hold bleach just to finally kill any remaining green.

    Rinse thoroughly, maybe with a little soapy water

    Good luck

  236. Ruth | Oct 28, 2013 | Reply

    Hi Ian

    I have a smooth, black, Welsh slate countertop, which was perfect at installation, and now is speckled due to lime and lemon juice spills. My slate supplier said to use steel wool to remove the Lithofin sealer and then re-seal. I’ve tried this but the outline of stains does not diminish. Any clues please? A webpage suggested baking soda and lemonjuice applied overnight … Help! Thanks for any advice …


  237. Ian Taylor | Oct 30, 2013 | Reply

    Hi Ruth,

    OK, well Welsh slate is so dense that not a great deal of sealer actually penetrates the surface. So what sealer is there tends to coat the surface and is therefore prone to easier removal – by use, including abrasion and from exposure to chemicals. Some sealers are better than others are resisting acidic chemicals (like lemon and lime juice). I don’t know exactly how that one will have done

    It is possible that there is a slight stain from the juice (that has got past the sealer) or, it could be that the acid contained in the juice has simply damaged the sealer and partially removed it. If this is the case then all is not lost, but attempting to clean it is not going to achieve any thing. You may need to remove some of the sealer – (what you are thinking of as a speckle stain, might actually be the actual slate, where sealer has been removed). In any event try a small test on one of the affected areas using some acetone (if you have some clear nail varnish remover this will do) rub a little NVR on a cotton pad and rub over the affected area – if it makes the speckle apparently bigger then it is removing sealer from the surface – making what you see as the problem ‘bigger’ but in reality is just cleaning the sealer off the slate. let it dry and see if you are now back to a clean slate surface. If so then you can try to re seal that area. If it is possible to reseal in just those spots affected (without it looking patchy or inconsistent against the older seal) then go ahead. If not then you would have to consider stripping the entire surface (or at least a whole section). It might be a pain to do the whole slate with NVR, so you could try to get a proprietary sealer remover

    Hope this helps


  238. Dan | Jan 26, 2014 | Reply

    Hi Ian
    I’ve just had a green/grey slate floor fitted.

    I’ve noticed that some of the tiles have white marks on them. These appear to be along the contours of some of the tiles. It’s not on all of them though.

    Would this be efflorusence?

    The tiles have been recently sealed, what can do to remove the marks?

    Thanks very much for your help.


  239. Ian Taylor | Feb 3, 2014 | Reply

    Hi Dan,

    It could be efflorescence, slate being very dense, any moisture that may be trapped in the structure is likely to escape via the joints, and so that could account for a mineral deposits along the edges and corners. IT could also be small bits of over application of the sealer (if the sealer was left to pool in the joints, as it runs off the slate etc) then you can get small shiny/white spots where too much sealer was left on.

    A quick test: wipe the marks with a damp cloth, if they seem to disappear or at least become translucent, but come back when dry) then this is consistent with efflorescence and a very mild acidic cleaner ought to help – use a safe acid based on phosphoric acid or sulfamic acid, and dilute it well, pre-dampen the floor first with water and rinse well after. Try not to let the floor stay wet for long, do a little bit at a time, and dry it with a towel, this way you reduce the likleyhood of creating additional efflorescence through the added moisture.

    If the test does not make the spots disappear, then it might be that you have sealer residue spots instead -and they would need to be removed with the sealer stripper, or you could try some clear nail varnish remover on some cotton pads.

    Hope this helps


  240. Bob Lynn | May 27, 2014 | Reply

    I have white stains on my flagstone that won’t come out even when I use diluted phosphoric acid.

    The problem started when I used Quikrete PowerLoc Jointing Sand to fill the joints.

    I can send a picture if you give me an email to respond to.

  241. Ian Taylor | Jun 2, 2014 | Reply

    Hi Bob, apologies, I missed this one. Yes send ma an email ( use the contact us page on the site)



  242. Bob Lynn | Jun 6, 2014 | Reply


    I emailed the pictures to you last week. Did you get them?

  243. Ian Taylor | Jun 27, 2014 | Reply

    Hi Bob, Sorry, no I have not received them



  244. Bob Lynn | Jun 28, 2014 | Reply

    I sent the pictures to the donotreply email address which obviously doesn’t work. What email do I attach and send the pictures to?

  245. Ian Taylor | Jun 30, 2014 | Reply

    No Worries, there is a contact us form on the site most people manage to contact me that way, once you send me a quick message I can reply and you will have my email address



  246. Richard | Jul 27, 2014 | Reply

    Hi Ian firstly great blog

    I have a slate floor I didn’t like the original grout so I removed it using a buzz tool, unfortunately when removing it the tool would sometimes jump out the grout lines onto the slate leaving a lovely scratch. So I have now replaced the grout and buffed out the scratches, however where I have buffed out the scratches the colour is lighter than the rest of the tile. Can you provide any advice on how to get the same colour back? I have sealed it several times and have also sealed the affected areas only several times and the buffed areas are still pretty noticeable.


  247. Ian Taylor | Jul 28, 2014 | Reply

    Hi Richard,

    OK, first of all is your slate dark? – like dark grey or black? Often scratches in this type of stone look white or very light grey by comparison.

    What I don’t know is if there was originally any kind of stain (dye, oil, unlikely) applied to the slate which imparted an artificial colour, or, an enhancing sealer – (perhaps more likely). If so then scratching through the surface also removed whatever had been applied.

    IF this is the case then you would need to know what it was and apply a little more BUT, that may not be possible now that you have sealed it several times.

    However I think it more likely that the scratches are much lighter just because the finish of the slate may be smoother than the surface left by the scratch. The rougher the surface, the dully/lighter the colour.

    It is my guess that the buffing you have done, has blended the scratches and made then smoother than they were (reducing their intensity) BUT, has not reached the same level of fineness as the rest of the slate. What did you use to buff? – a cloth would not do much, and sandpaper would leave the surface too rough. You might try the finest wet and dry emery paper.

    Have you got an photos you could send me so see if it helps further?

    Hope this helps


  248. Heather | Jul 29, 2014 | Reply

    Hi Ian,

    My husband brought home an old schoolhouse chalk board slate piece this past weekend that had a few paint marks and other etched areas, so I looked up how to remove paint marks, and an internet source mentioned acetone, so I pulled out the generic “acetone” that I use for removing nail polish and it seemed to work on some of the varied colored paint stains around the border area (where there was most likely a wooden frame) so after testin it, I went at it. However, there was another area that I assumed was green paint somewhat in the middle of the slate, so I put the acetone on that and rubbed aggressively, and it seemed to make the spot even bigger and greener! Ahhh! Now I fear that I ruined my salvaged piece. I cleaned the entire slate with soap and water and then followed up by drying it with a paper towel, but the (now bigger) green mark is still there. When I wipe the slate, dark discoloration does seem to appear on the paper towels, by the way, which seemed strange to me because I don’t remember that happening when I cleaned classroom chalkboards with water for my teacher as a child. Please advise about what I should do to possibly fix my bigger, green, revealed smudge/discoloration. I am so sad :(

  249. Ian Taylor | Jul 29, 2014 | Reply

    Hi Heather,

    Hmm, interesting one. Sometimes these problems can be the opposite of what we think we are seeing. Can you tell me, is the back of the slate also black? I think there may be a slight clue in your own word: “revealed”

    I am thinking that instead of spreading a discoloration, the black colour (which comes off on the cleaning towels) is actually the discoloration – or, if you like the ‘intended, deliberate ‘coloration’. What I am getting at is that perhaps it is in fact a GREEN slate, that has been died, stained or painted black for use as a chalk-board. And so your use of acetone has broken down the ‘paint’ and now that is more easily removed, ‘revealing the natural slate colour beneath – only one way to test this though; try some more acetone in an inconspicuous area, maybe on the back? See if it takes black colour off to reveal a green slate.

    In your part of the world there are some very good quality slates (very dense, hard-wearing, able to be fine-honed to give the smooth writing surface required) but they may have been more green in colour, and so were painted to make chalk boards.

    Do a quick Google search for “Vermont green slate” – see if the images you find look like the green you can now see

    If this is the case, then there is nothing you can do, as restoring the slate means either stripping all the paint off it to reveal its natural (and rather beautiful) green colour, or, painting it an artificial black again.

    If my guess is wrong, then I am not sure, it is odd that the black colour comes off. Some dark grey/black slates do have green patches in them; this is natural and to do with the mineral content being unevenly distributed in the stone – this image I found shows the very common green spots found in Welsh Slate (source:

    It is possible that your slate is dark grey/black but had some natural green patches which the previous owner masked with come kind of paint or stain – I could not advise on what would be a suitable product to re instate this as it is gpoing to be an nunatural coating of somekind (paint, dye etc)

    What happens to the green patch, when you simply wet it? does it go dark and black or is it still clearly visible as a green albeit now wet, patch? If it disappears then many stripping the slate and sealing it with an enhancing sealer could be the way to go

    Hope this helps


  250. sharon | Aug 1, 2014 | Reply

    Have just had a new slate patio completed. Yesterday I noticed yellow stains from where my dog has walked on it. I couldnt think what this could be but just realised that I had put weed and feed down on the lawn and think it must be this carrying back onto the patio on the dogs paws!! Is there anyway of saving my patio???

  251. Bridget | Sep 7, 2014 | Reply

    We built a beautiful hearth out of natural grey-blue slate but used WD40 to seal it which has turned it black. Will it return to its original colour? Is there any way of removing the WD40?


  252. Ian Taylor | Sep 8, 2014 | Reply

    Hi Bridget,

    This is no uncommon I am afraid, some slate hearth installers do seem to suggest this ‘old trick of the trade’. Basically it is just a thin oil, and your slate (if Welsh, or Cornish etc) is likely to be very dense, so the oil will not have penetrated all that far. It should fade with time, especially if you wash the slate regularly.

    You could try using some warm water, and a scrubbing brush (even a nail brush) and a little washing up liquid give it a good scrub and wipe away the soapy suds with paper towels. then rinse with fresh warm water and dry with paper towels or other absorbent material. let i dry and see if you have lessened the effect. If not you may need ot try a high alklaline cleaner such as my Xtreme Clean which you can find on Amazon by searching for: Heavy Duty Tile & Grout Cleaner Xtreme Clean for Stone, Tile & Grout 1Litre by All For Stone. Hope that helps


  253. Roy Skeaping | Sep 23, 2014 | Reply

    I have just had fire installed with slate slips around it. Unfortunately the builder has left a couple of patches of resin based mortar on the slips, any advice on removing them?


  254. Ian Taylor | Sep 25, 2014 | Reply

    Hi Roy,

    First try to gently scrape any physical residue away with a plastic scraper (as metal may scratch).

    Try a solvent stripper, paint stripper, or acetone nail varnish remover – to see if you can draw out and remove any resin stains.

    You may also need a phosphoric acid based cleaner to remove any latent cement staining.

    If you cannot remove it 100%, you may be able to apply an enhancing sealer such as Enhance n Seal to darken the whole slate, and mask the problem. (provided the slate has not been previously sealed)

    hope this helps


  255. Debi Kaye | Oct 6, 2014 | Reply

    We bought natural shaped slate stones and set them in Quikcrete cement as a foyer in our rustic Adirondack home. The cement left a film and some spots I neglected to clean up fast. HELP! How do I get rid of the cement with out ruining the cement between the stone?

  256. Ian Taylor | Oct 8, 2014 | Reply

    Hi Debi,

    The normal route here is to use an acidic cleaner, but one designed for the job.

    First confirm that the slate itself is not sensitive to acid (ask the supplier, do a test on a spare piece etc)
    Secondly, stay away from Hydrochloric acid products (muriatic) – far too strong, can do damage to grout joints and lots of other nearby surfaces.

    Instead try a cleaner based on phosphoric acid or similar- plenty of brands around just ask the supplier of visit the web site of the product.

    This will do minimal damage to the grout joint as it is mild, works on very thin layers at a time – it may need several attempts in order for remove all the residue

    follow this procedure:

    1. Pre-wet the floor – this saturates the cement joints and helps prevent the acid doing much damage to the surface
    2. Dilute the phosphoric acid based cleaner as per instructions (weak to begin, you can go stronger later if you get nowhere)
    3. Apply to small test area of floor, leave a few moments and scrub with a white pad, scrub brush or similar
    4. Pick/mop up solution and rinse well with water
    5. let dry and repeat if necessary – buff floor dry with a terry towel – all this helps remove the problem, don’t just wash it and let the water dry

    If you cannot use an acid (because the slate is sensitive, unlikely but possible, esp on rusty/autumn colours) then you may have to take an abrasive approach, try a safe abrasive cream cleaner, failing that go progressively more course with honing powders – speak to a stone care professional/providers for product suggestions

    Hope this helps


  257. Debi Kaye | Oct 8, 2014 | Reply

    Thanks so much. Done and done! Great results!

  258. Sally Panter | Nov 2, 2014 | Reply

    Dear Ian,
    I have read this blog with great interest. I have recently had my new kitchen worktop made out of 3 sections of reclaimed snooker table slate. It has very smooth surface but has not yet been sealed or cleaned. I ‘d like to wipe it down first of all and I am nervous about what cleaning product to use. When you say mild neutral product in the blog-what do you mean? Could you mention one or several products by name so I know what to go and buy please?
    Also I haven’t decided on whether to use a sealant or not yet . It’s been suggested to me that treating it may bring out stains from it’s previous life. I ‘d prefer my slate to stay the lighter grey it is now if I can. I don’t really want it to have a darker colour like when wet.Is this realistic though? Any idea whether it is can look ok to leave it and just develop a patina???

    I have had recommended to me a product called Lithofin. . This product can be used on a surface where there will be food preparation etc.

    Do you know if it is effective?
    I ‘d be grateful for feedback before I proceed.Thanks Sally

  259. Ian Taylor | Nov 5, 2014 | Reply

    Hi Sally,

    OK, well first of all, all I mean by mild or neutral, is a neutral, or near-neutral cleaner – i.e with a ph value of 7-8. it is just good practice to avoid harsh chemicals, especially acids, but also high alkalines for REGULAR or ROUTINE/every day cleaning.

    However your slate is likely to be very resilient and not acid sensitive. One neutral cleaner is my own, EzyClean by All for stone, but there are plenty of others in your local tile/stone shops.

    As far as sealing, avoid a sealer designed to enhance the stone, as they will darken the stone a lot and they could bring out any stains etc.

    So, go for sealer that is designed to maintain the natural look, the one you mention is fine, however it is solvent based and there is a small chance it could darken the slate ever so slightly – but not so much that it will change the look of the stone. the slate is pretty resistant to stains to be honest but it can show greasy marks and a sealer will help with this – it is your call but as it is a work surface, if it was mine, I would probably seal it

    hope this helps


  260. Linda | Nov 17, 2014 | Reply

    We’ve inherited in iur new house a slate hearth on front of our wood burner. It therefore gets plenty of abiuse with tools and wood etc around it. I’ve noticed it’s getting marked as well as patchy loose of colour – black. Looking more grey. Any thoughts of what we can do to make it look better?

    Many thanks

  261. Ian Taylor | Nov 19, 2014 | Reply

    Hi, ok, well it is natual stone, and although very hard, it is not as hard as steel or iron, also it,s nature is to cleave naturally along flat planes, which is why it is so easy to work with and make roofing tiles etc.

    So, impact from metal tools, especially heavy pointed ones, will chip it and cause surface flakes to come off, very small chips and indentations will be hard to prevent in those conditions. As for the black going grey, well, the stone may have been treated or fine honed (like being polished) and this could have darkened the surface (it could have had slate oil or an enhancing sealer applied, or even just some wax)> as the surface is removed it reveals the more Natural lighter grey beneath. You could try applying some wax – just to a small spot, see if that helps. failing that, can you contact the supplier and find out what treatment the slate was given in the first instance?

    Hope this helps


  262. Linda | Nov 21, 2014 | Reply

    Many thanks will do so

  263. Judith | Nov 26, 2014 | Reply

    Hi there Ian,
    I was wondering if you have any advice about how to clean up a smooth slate hearth. It’s black but with lighter marks that look like drips all over it, they look like possibly wax drips ( there’s no wax on the surface) or oily drips. It’s really spoiling the look of the fireplace. I don’t know what the drips are from as we just moved into our house. Any suggestions would be gratefully ( no pun intended)

    Thanks in advance.

  264. Ian Taylor | Nov 27, 2014 | Reply

    Hi Judith,

    It sounds like oil or wax but could be any thing really. Try some alkaline cleaner, I have one called Xtreme Clean it is available on Amazon (I am not linking to it as it harms the blog ratings).

    but you could also try dabbing some clear nail varnish remover (the old type with acetone) using a cottoin wool pad, see if that brings anything off. Feel free to come back to me if not

    Hope that helps


  265. Clare Kelly | Nov 28, 2014 | Reply

    Hi Iain,

    I was wondering if you could offer some advice on how I can repair the surface of my tiles? We have a black slate tiles in our bathroom – they have a smooth satin finish (not gloss) and an even tone. Last weekend my husband accidentally splashed Viakal on them and it left white slightly rough patches that I could not remove with ciff. From reading the previous posts it seems that some sort of chemical reaction has occurred and damaged the surface of the stone. I tried diluting the Viakal and rubbing the tiles again to see if that woul remove the white splashes as I thought they might be like scale (you suggested this in an earlier post) however that lightened the whole tile slightly. What’s the best thing to do here? Will re-sealing disguise the marks? Can I dab a little acrylic paint over them?


  266. Ian Taylor | Dec 19, 2014 | Reply

    Hi Clare,

    OK, first of all apologies for my late reply – I have been away from the computer for a few weeks and not had so much time to check the blog. I had a quick look at the msds for the product, it contains some acids, this make sense if the product is designed to remove limescale. What you are describing sounds like etch marks, whereby the acids actually remove some material, and chemically ‘roughens-up’ the surface, making it whiter in appearance. However this is not typical with most black slates (they are usually not very sensitive to acids) it is possible though that your slate has a degree of calcium in its make up (they are normally made of clay and other minerals that do not react with acids, but there are lots of variations and also the, while the geological term for slate might be quite ‘fixed’ in practice, in the world of stone sales, the term ‘slate’ can be a little more loosely applied and encompass several different, similar stones).

    In any case, it sounds like there is something either in the make up of your slate, or something that has been aplied to it (with or without your knowledge) that has been removed, or partially removed by the cleaner.

    I thought at first it could be some kind of deposit from the cleaner, but as you have tried diluting it and wiping it away and that made more of the surface lighter, I feel pretty sure there is some etching going on.

    It could be that there is some kind of factory applied coating, sealer or wax type product that has been applied to make the slate look more even and ‘black’ and that this has been removed leaving the natural or actual surface. Can you check this with the supplier?

    What happens when you dampen the surface, so if you wipe over the white areas with a damp cloth, does the whiteness temporarily disappear?

    If so then it might be possible to use an enhancing sealer so seal them and also maintain that darkened, even look – however you would have to do the entire slate, and also, if they had been sealed or treated with anything else first, you would have to know with 100% certainty that you have first removed it all – not necessarily easy.

    If the tiles are fine-rubbed or honed (as you describe them, satin smooth, but no real shine) then the etching has made the surface less well honed, it can be re-honed using diamond hand pads – you may need several grades and it can be hard work, and in situ on a wall it can be hard to get an even finish – but if the surface is ‘damaged’ by an acid this may be the only way to restore it.

    Do you have any pictures?

    Please feel free to come back to me with any further questions – hope this was some help


  267. Mark Wilkinson | Dec 29, 2014 | Reply

    Hi Ian.,

    I have a slate that has delaminated in my shower.. Is there any adhesive you can recommend that would stick the delaminated piece back down..? I don’t want to attempt removal of the rest of the slate as I don’t want to disturb the waterproof tanking in the shower floor..

    Any help would be greatly appreciated as we are yet to use the shower in our newly finished bathroom.!

    Many thanks.,


  268. Ian Taylor | Dec 31, 2014 | Reply

    OK, you might have to be a bit inventive here; any adhesive, like tile adhesive, be it ready-mixed paste or powder, is going to have an aggregate in it – usually silica sand – and that means it will be gritty and have a ‘thickness’. This will not be great as it will not allow the slate flake to bed down in its original position. So you want a water proof liquid-thin adhesive. In the past I have achieved this with water proof PVA type adhesive, as long as it can be diluted (to thin it) and still be waterproof. Look for unibond or something like Bal Bond SBR – mix this with a little water, and paint it onto the flake and the remaining slate piece and press together (leave a weight on it once you have made sure it is in seated correctly in place, wipe up any surplus that comes out of the edges right away with a damp cloth. Leave it for a few hours.

    Hope that helps


  269. Jessie | Jan 10, 2015 | Reply

    Hi Ian,

    Hoping you can help with my problem. I have a slate built inglenook fireplace, but a chimney leak has caused staining on the slate walls. I fear this may be soot or tar brought down by rainwater which appears to have run down the walls.

    Will I be able to remove this staining, and what would you suggest I use?

    Any suggestions gratefully received.

    Many thanks.


  270. Ian Taylor | Jan 12, 2015 | Reply

    Hi Jessie,

    Soot and other carbon deposits can be tricky, when they are burnt on, but if they are deposits that have washed down due to rain then they should be easier to remove. Also slate is typically pretty dense and does not stain quite as readily as some more porous stones (depends on the particular slate of course but for an inglenook I am imagining you have a black, native British or similar slate which by and large would fit my description.

    So, you can try a scrub pad or brush just with soapy water – never know, always worth a try. Failing that you could try an alkaline cleaner like (Xtreme Clean by All for Stone). IF it is really stubborn you may need an acidic grout remover type product, but I would try the Alkaline first. I also have a cream abrasive, called All for Stone Microscrub which can be used on its own (with a little water) or in conjunction with the Xtreme Clean), it can help gently scrub off the deposits if they are stubborn. they are available on Amazon – I cannot link from here as it affects the page rank negatively.

    Hope this helps


  271. Jessie | Jan 12, 2015 | Reply

    Thanks Ian for your reply.
    I have tried scrubbing with soapy water and also a diluted general purpose cleaner, but with little effect.
    I’m not sure if the stains are ‘burnt on’, I do have a multifuel stove in the inglenook which might have prevented that but they are certainly very difficult to remove ! The slate would be Delabole slate by the way.
    I shall order the alkaline cleaner today and hopefully have success.
    Thank you so much for your reply and help.


  272. |Rodney | Jan 19, 2015 | Reply

    Hi- a great resource for people to sort out their slate problems- on behalf of everyone, thanks for your time and sharing your knowledge.
    My problem is slightly different (I think- sorry if I;ve overlooked a suitable reply). Our multifuel stove has a polished black slate hearth. Not sure what it was sealed with originally, but my wife regularly treats it with Slate dressing and polishes it off. But when sleaning the stove door glass with caustic gel (Stovax- 18% KOH), I dropped some on the slate. Wiped it off as quickly as possible and washed with water, but it has left a dull-looking match that feels not-as-smooth as the rest. Applying Slate Dressing makes it look fine until it dries off then it is just the same. So, is caustic just as bad as acid? What can you recommend? Thanks.

  273. Ian Taylor | Jan 20, 2015 | Reply

    Hi Rodney,

    OK, first of all, in this particular case, caustic is WORSE than acid: Acids burn and etch , but only acid sensitive materials and typically (but not always) slates tend to be pretty resilient and don’t usually react with acid cleaners. The caustic material is not likely to have done any permanent damage to the actual slate though. Clearly there is some kind of coating on the slate that the KOH has stripped off. This coating may just be a build up of the dressing (if it is oily in nature), or perhaps more likely some kind of sealer/polish applied at the factory or by the installer, they often use slate oil. This would be my line of thought anyway, it is possible that just adding one quick wipe of dressing is no where near thick enough to make up for the initial coating that was applied (and now stripped). It might be possible to research a slate polish and re apply one.Or it might be that you have to strip it all back to the same finish and start again.

    Hope this helps


  274. Laura | Jan 21, 2015 | Reply

    Hi, this website is brilliant. I have tried to look through previous questions and replies and I’m very sorry if I’ve missed my answer. Hope you can help-
    Here goes, we have a dark grey/black slate tiled wet room, on the floor near the drain, lots of white/cream water marks have appeared.. Some in the grout lines and the rest all across the tiles. We have been advised to use a tile clear before resealing it as was told by a friend who used to be a plumber that is was due to the sealant wearing off. So we have used ‘Maintain’ tile and stone stain remover (from tops tiles) says that it is a powerful cleaner for ceramic, porcelain and natural stone. However after scrubbing and scrubbing, the unsightly large white marbling affect marks are still there??
    Please help?
    Kind regards Laura

  275. |Rodney | Jan 22, 2015 | Reply

    Thanks Ian! I’ll try to find out what the suppliers treated it with initially.

  276. Laura | Jan 25, 2015 | Reply

    Hi Ian,
    What a great website! I have looked through a lot of the posts so am very sorry if I have missed my answer.. Hope you can help.
    We have a Grey/black slate tiled wet/ shower room, in which a lot of the tiles on the floor are now covered in white marbling effect water marks ( I will email you a picture) we have been advised by a plumber to use a tile stain remover before re sealing it as apparently the seal may/ will have worn off- so we have scrubbed and scrubbed but unfortunately to no avail.. the white/grey marks that are in between grout lines and across the tiles are still there. Do you have any suggestions as to what we can use?
    Many thanks in advance.

  277. Ian Taylor | Jan 26, 2015 | Reply

    Hi Laura,

    You have posted the same (basically) question from two email addresses? – just checking that I only need to answer once.

    OK, from the second post, you drop a clue, that the white marks are in the joints also.

    You have tried a maintain stripper? – don’t know this product but likely to be either alkaline or solvent based. This would remove grease/grime or sealer coatings and residues.

    However it will not remove mineral type deposits. So, for example, cement residues (from grouting) or efflorescence.

    I think your water marks are exactly that – marks caused by the water, NOT as the plumber suggests, the sealer wearing off. If it were a coating sealer that has begun to wear then the alkaline or solvent stripper ought to have at least partially removed them – or even made it worse (as it further damage the sealer)

    To eliminate this completely try rubbing a little clear nail varnish remover on the white marks – see if it takes anything off, if so it is pointing to the solvent being the way to go it just may take more than one try.

    However I suspect it might just be a build-up of hard water deposits and or efflorescence – the pictures you are going to send me may help

    So, it can be a deposit of calcium or similar from water, and / or soap scum (a deposit that forms when soap is added to ‘hard’ or mineral rich water) Looking at your ip address I think you are in a ‘moderate’ area as far as hard water is concerned, but even so these deposits can build up.

    Efflorescence occurs when calcium or other minerals are dissolved in water and are then depositied at the surface of the tile and grout as water evaporates, this can come from the initial grouting/installation water.

    In either case an alkaline or solvent based cleaner will not do anything, but an acidic one should.

    So, try, in a small area an acid based cleaner – there are several on the market DO NOT USE A BRICK ACID OR ANY PRODUCT CONTAINING HYDROCHLORIC ACID – instead find one based on the milder phosphoric acid or similar (these are designed to be weak and may need to be used more than once to remove all the deposit)

    You could try a small test with some neat vinegar, just rub it over the white marks and see if any thing is removed, if it does but not much, go buy one of the products I suggest (my own Grout Haze plus is such a product and Stokes Tiles from Sheffield have it in stock, and they have a branch in the Manchester area I think – but there are others out there.)

    When you get it, dilute it, follow the instructions and make sure it does not come into contact with any acid-sensitive surface (like polished marble etc). Rinse well afterwards. I’ll look out for your pictures but I think this may solve your problem.

    Hope it helps


  278. Jason | Jan 30, 2015 | Reply

    Hi Ian,

    Great resource and interesting reading. I’m looking for guidance in how to remove sap deposits from a smooth slate hearth. In most cases these have hardened into small solid lumps… Any guidance you can offer would be appreciated … Thanks

  279. Ian Taylor | Jan 30, 2015 | Reply


    OK, for thick, sticky resinous sap i would suggest first, finding a plastic scraper and trying to remove as much of the hardened solid material as you can, Using a plastic scraper so as not to scratch the slate, but would will still need to be careful.

    Then you will have to remove the residues. Many web site talk about using various oils and WD-40 to remove sap, this may work on some substrates but I would caution against it here simply because we don’t want to add the possibility of staining the slate with oil as well.

    My guess is you are going to need a solvent of some kind, you could try nail varnish remover as it contains acetone, or Turpentine (which is also derived from tree resins to my knowledge). The key will be to test , leave it on for a short time, but long enough to soften the resin/residue. Then use a fine white scrub pad to loosen all the residue, then pick up with absorbent paper towels or similar.

    If the slate was previous sealed/oiled/treated in any way, then the process of removing the sap may remove or reduce this treatment so you may need to reapply it or top it up

    Hope this helps


  280. Jason | Jan 30, 2015 | Reply

    Ian – You’re are star, thanks for getting back to me. We’ll try some of your ideas and let you know how it goes. Thanks again…

  281. GAYLE | Feb 5, 2015 | Reply

    needing some help I have a slate frontage facade on the front of my home that has developed a fair bit of rust making it unattractive. it will be a big job how do i go about getting it removed will high pressure cleaning remove it. hope someone has an answer as the slate companies don’t reply to my emails thanks gayle

  282. Ian Taylor | Feb 6, 2015 | Reply

    HI, it depends on the slate itself. For example here in the UK we do not see too much rust occurring from within the slate, but we could see rust being deposited on top of the slate (from water run-off from watering plants in metal containers for instance) In this case it is a fine layer of rust being left on top of the slate.

    However many other slates, in particular some form Africa and China, may have a lot of iron-bearing minerals within the slate. When the slate is cut, a new face is exposed to the elements for the first time. Over time this now exposed surface can start to react and the iron element can oxidize now that it is exposed to the environment.

    If this is a fine powdery coating that brushes off on your hand, then you can try just dry brushing it, much of it may come off this way. If you have a heavy deposit of rust then you may need to use an acidic cleaner – typically one based on phosphoric acid is best. Just make sure that any acid cleaner used is not allowed to come into contact with any other surface that may be sensitive to acids. (for example if you have a slate facade but a marble floor – you need to figure out how you are going to stop the run off getting onto the floor and ruining the marble etc).

    IF you have the first scenario then this may work and be fine for a while (or until you allow more rust to build up). if it is rust from within then it is going to depend on how deep the oxidization goes- if just a the surface then it may clean up quite easy. However bear in mind all the water you just used, and the ongoing exposure to the elements may cause it to begin to rust again. The application of a mat impregnating sealer after cleaning and drying may help with that as it will reduce the amount of water that can get to the surface from that point on but it may not stop it completely.

    Hope this helps


  283. GAYLE | Feb 7, 2015 | Reply

    thanks so much for your advice it has taken six months to get any info bit sad when im in australia and get quick answers from the other side of the world this is a fabulous sight and much appreciated.cheers to you. kind regards gayle

  284. Neil | Feb 28, 2015 | Reply

    I have used a cleaning product on my slate floor tile to remove some adhesive residues. It seems to have left what looks like a rust mark what is it? And what can I do to remove them? Help please!

  285. Ian Taylor | Mar 2, 2015 | Reply

    Hi Neil,

    That is interesting cleaners don’t normally leave rust coloured marks. I might need a bit more information. At a guess, as you say ‘adhesive residues’ I am going to guess that you used an acid-based cleaner of some sort. What can happen is that some stone, and in particular slate, can have iron bearing minerals as inclusions in their natural make up; for example, iron pyrite sometimes acids can react with these but to be honest, regardless of what type of cleaner you used, you inevitably used water. Water alone, if it comes into contact with these minerals can set off this reaction, which is basically the iron pyrite rusting.

    You could try, ironically perhaps, cleaning the spot with a little phosphoric acid based cleaner – it is sometimes effective on rust. However as this may be an integral part of the stone you may not be able to remove it. Apart from replacing the individual slate that is.

    Hope this helps


  286. Neil | Mar 2, 2015 | Reply

    Thanks I very much appreciate your comments. Yes it was an acid based product! Them washed off with plenty of water. Guess I’ll give it ago at scrubbing and then if all else fails I’ll have to remove the tiles :-(

  287. george | Mar 3, 2015 | Reply

    Hi there

    First thanks so much for your generosity in answering all these questions with such attention. Great Job! We have a slate floor and it got paint spots in it during a re-decoration. I stupidly used a brillo pad to sand the marks off and have scratched the floor in quite a few places. I think it has been treated/sealed but quite a few years ago. Have you got any advice on how i can even out the colour/stains or get rid of them somehow? Names of any products and where to buy them would be great.

    Thanks, George

  288. Ian Taylor | Mar 4, 2015 | Reply

    Hi George,
    OK, you don’t mention what finish your slate has, i.e if it is naturally riven or smooth/honed etc.

    To remove any remaining paint you may have to resort to a paint stripper, you could try a little nail varnish remover just to see if that helps, try dabbing and absorbing with a cotton wool pad soaked in a little nail varnish remover, don’t push and rub too hard so as not to disperse the paint deeper/further out. Immediately wipe with absorbent paper towels then rinse with clean fresh water, repeat if required.

    That should remove the paint. But it will also take away some of the sealer – if there is any, however you have done this with the brillo pad anyway.

    What I am not sure about is if you have scratched the actual slate surface and/ or a coating. I would imagine that as you are not sure if it was treated and if it was, it was several years ago, that any coating type sealer would have worn away anyway, so there may be an impregnating sealer, or what remains of one.

    Has your brillo pad rubbing changed the texture of the surface and the shade / colour?

    if you were able to send me a picture ( I may be able to provided better advice – could do with knowing what the surface of the slate is like really.

    Hope this helps


  289. george | Mar 4, 2015 | Reply


    Thanks for your prompt response. Much apreciated. I have got all the paint off with the brillo and turpentine. I will email you images of the floor which is large slabs with irregular ridges etc. The brillo has lightened the shade of the slate so there are lighter slightly textured marks on the slate.

    I am emailing over now.


1 Trackback(s)

  1. From Slate Kitchen Floor - Rebootmyhome | Jun 5, 2012

RSS Feed for This PostPost a Comment

Get every new post delivered to your inbox
Join millions of other followers
Powered By