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Tile and Stone Maintenance

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.


  1. 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?


  2. 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


  3. Hi,
    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?


  4. 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


  5. 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?

  6. 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


  7. Thanks so much. Done and done! Great results!

  8. 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

  9. 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


  10. Hi
    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

  11. 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


  12. Many thanks will do so

  13. 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.

  14. 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


  15. 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?


  16. 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


  17. 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.,


  18. 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


  19. 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.


  20. 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


  21. 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.


  22. 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.

  23. 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


  24. 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

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

  26. 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.

  27. 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


  28. 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

  29. Hi,

    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


  30. 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…

  31. 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

  32. 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


  33. 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

  34. 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!

  35. 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


  36. 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 :-(

  37. 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

  38. 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


  39. Hi.

    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.


  40. Hi there

    We found some slate behind the back of the shed which we would like to use as a window sill in both the kitchen and the bathroom. We cleaned it with an acid cleaner suitable for brick, mortar, stone etc. I really like the black look of the slate when it is wet rather than the light grey patchy look. What product could I use to blacken the slate and keep it black whilst also protecting it from water stains etc. I’d rather have a matt or satin finish rather than a shiny/glossy one. Items such as washing up liquid, toothbrush holders, toiletries etc. will be placed on these slate windowsills so they need to be protected from water stains/rings, toothpaste etc. These are in a rental property so whatever product I use, it needs to protect and maintain the black appearance of the slate and cope well with whatever the tenant throws at it. Is there such a thing? I am considering Lakeland Worktop Wonder, Calfire Slate Sheen, WD40. I have heard of Lithofin Slate Seal but this is not recommended for bathrooms. Do you have any suggestions of a suitable product please?

  41. Hi Mandy,

    OK, so you need a Matt finish, natural finish, colour enhancing impregnating sealer that will seal against staining and maintain the wet look without adding a shine.

    I can recommend a perfect product for this, it is one of my own products (and of course there are others out there) but this is one of the best, WD40 – that is an old slate fireplace installer’s trick – its just a thin oil and it will not last. Don’t know the lakeland product and the other one as the word ‘sheen’ in its name.

    Search for this on Amazon – sorry it is not a live link but Google penalize the site if I link out to it: – Enhance ‘N’ Seal 500 ml Colour-Enhancing Impregnating Sealer

    You have you use it carefully, and correctly, follow the instructions, and make sure the slate is dry when you do it and keep it dry for a day or two after. Contact me with any questions BEFORE you do it via the contact us page

    hope this helps


  42. Hi,
    I’m hoping you might able to advise on how to remove render stains from a slate hearth. I’ve recently had a wood burner fitted and its sitting on a riven slate hearth, when the builder rendered the inside of the fireplace splashes landed on the hearth, these were left long enough to stain. I’ve tried a phosphoric acid cleaner but the test patch turned the slate a dull grey colour. Any help would be really appreciated. Thanks, Sam

  43. Cheryl Lovell

    May 31, 2015 at 7:52 pm


    Ive been reading your blog with great interest. I’m at my wits end. we have just had a hones black slate floor laid. the tiler sealed it with topps tiles colour sealer before grouting. After grouting, there was a white milky coating to the tiles. He assured me that Topps tiles grout residue remover for honed floors would remove the film if applied neat. this did improve, however we ran out and bought a QEP grout residue remover from B & Q., following the instructions and applying neat. when the floor dried, some tiles were worse than before. Parts of some tiles appear to have been bleached and others have this white milky film that we cannot remove. the grout has also changed colour from grey to white. Have you please got any suggestions as to what I could do ?. thank you in advance.

  44. The acid would have helped but if it has dulled the slate then it is reacting to something else other than just the cement, is there any dye or stain on the slate? A phosphoric acid cleaner is not so strong that it would attack most slates directly.

    If the cement in the render had managed to penetrate the surface slightly then it could be traces of the cement that has gone grey due to the acid. You could try a micro-abrasive cleaner like Microscrub (from All for Stone, it is on Amazon) – it may help, by virtue of the mild abrasion.

    However it may nor do anything for the area you have already etched or damaged, that may need rubbing back with diamonds or some fine emery paper.

    hope this helps


  45. OK, a bit of detective work is needed here.

    the grout was applied after the sealing – but how soon? – And, how soon after installation was the sealer applied or was the floor cleaned immediately prior to sealing with water?

    The white film could be either a grout residue film, (of cement and latex etc) or it could be the sealer itself, reacting to moisture as some sealers (in particular colour-enhancing ones) have a tendency to do. It could be that the sealer was not fully cured when the grouting was done, or that there was still installation, or cleaning moisture in the system when the sealer was applied, or both.

    Both the grout residue removers you have used are most likely based on phosphoric acid – or similar and this means they will attack cement and alkaline materials. This is born out by the fact that the grout has gone white (acid etching) – this is what I would expect form an acid wash – especially if used neat (it is almost always not necessary to used acid residue removers neat – far too strong).

    My gut feeling is that you have both issues here: the acid has attacked the grout residue – and the grout itself – hence the bleaching, but also the successful removal of SOME of the residue. But it has not touched the white film – if this white film is sealer gone white then the acid would not do anything

    So, I think you have got a thin film of sealer residue that has turned milky white – and on top of this, you have a (now partially removed) cement grout haze.

    I suspect that if you drop a little, say a capful of the neat acid cleaner on some of the grout residue it may fizz a little (you wont see the fizzing at diluted strengths but it still reacting/working) – do this, just as a test to see if there is still cement to remove, then treat the whole floor with DILUTE acid cleaner, scrub well and then rinse with clean water. When it dries try some paint stripper, or even some clear acetone based nail varnish remover on the milky white film – if it comes off, then this is indicating that this part is sealer residue and not cement – and you will need to buy a sealer stripper.

    So to sum up, you may have to first remove any remaining grout residue (dilute acid cleaner) and then tackle the milky white film left by the sealer that reacted with moisture (solvent stripper). The grout WILL be etched to a lighter colour but this will darken partially over time

    That would be my guess form the information you provided

    Hope this helps


  46. cheryl lovell

    June 2, 2015 at 8:45 pm

    Thank you so much for such a speedy and comprehensive reply. I have tried the remover again and there is indeed fizzing as you suspected. I will take your advise. You have been fantastic thank you

  47. your are welcome – good luck!

  48. Hi Ian,
    Any advice on deep cleaning slate in the bathroom, especially around the toilet? Also, is it possible to remove paint from slate?
    Thanks so much

  49. Hi Traci,

    Deep cleaning slate in the toilet area is just the same as anywhere else, you can read part 2 of this article also – In a toilet you may have mineral stains as well as general ones, so a mild acid based cleaner may help if an alkaline one does not do the job.

    Paint can be removed with the help of a proprietary paint stripper/remover

    Hope that helps


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