Cleaning Slate – Expert Advice on Cleaning Slate and Slate Floors – Part 2 »
By Ian Taylor on Mar 10, 2008 in Cleaning, Problem Solving, Slate, Stain Removal
Some detailed instructions with regard to cleaning slate floors:
If the slate floor is adversely covered in cement or grout residue:
1. Use water to pre-wet the floor.
2. Apply some Aqua Mix Phosphoric Acid Cleaner solution to the floor – mixed with 1 part cleaner to 5 parts water to begin. (You can use a stronger mix if required). **PLEASE NOTE: Always conduct a small test on a relatively inconspicuous section of the floor first, before you begin.
3. Leave the cleaner to dwell on the floor for a few minutes
4. Agitate the floor and cleaning solution with a scrubbing brush (nylon bristle and not metal).
5. Soak up the cleaning solution remaining on the floor. Rinse well with fresh water, agitating again so you can get rid of any residual acid cleaner.
6. Make an assessment of the floor at this stage. You may need to apply an additional treatment of the cleaner.
If your slate floor only requires routine cleaning we would recommend Concentrated Tile Cleaner – this is a mild cleaner and is safe and suitable for cleaning slate on a regular basis.
For more intensive slate cleaning, where the dirt is not mineral- based, we would recommend the use of Heavy Duty Tile & Grout Cleaner. This a powerful cleaner and decreasing solution. When applied to the floor, leave to dwell for between 5 and 15 minutes, depending on how bad the contamination. Then agitate by scrubbing with a nylon or natural bristle scrubbing brush. Clean up remaining the dirty solution and rinse well with clean water.
The critical elements here are the dwell time and the rinsing. Alkaline-cleaning solutions need time to work. Once you have “extracted” the dirt from the floor it will be suspended in the solution so you absolutely must remove it – on no account leave it to dry naturally.
amanda | Sep 19, 2010 | Reply
Hi
I hope you can help me. A couple of months ago we purchase a piece of slate to place under our pot belly stove, recently some diesel was spilt on the front of the slate, can you offer an advice on how I might attempt to remove it please?
Many thanks in anticipation Amanda
Ian Taylor | Sep 20, 2010 | Reply
Hi Amanda,
OK you could try a poultice. If the slate is very porous then I would first try cleaning with a high alkaline product like Heavy Duty Tile and Grout Cleaner; fist I would pre-wet the slate, all around the stain, BUT NOT THE STAIN ITSELF. This is to get warm water in around and possibly under the stain, I would do this to try to prevent the de-greasing chemical from pushing the stain further in. Then apply your cleaner to the stain, leave it for 10 to 15 minutes but keep it/everything wet, then scrub lightly and use an absorbent cloth to take away the liquid. Rinse and dry.
If this does not work, try a poultice: mix some Heavy Duty Tile and Grout Cleaner 50:50 with water. Then use this solution to make up a thin paste with Aqua Mix Poultice Powder, mix to a creamy consistency. Pour the poultice mixture over the stain, covering an area approximately 20% bigger than the stain. It will be about 1 cm thick. Now, cover the poultice with some plastic film, put a couple of holes in it and leave it 24 to 48 hours. If this is on a vertical face, then first make a ‘pocket’ with the poly-film and some tape, then our the poultice into it, seal the top but leave some space for drying.
Remove the no dry poultice carefully and inspect, if it the stain has gone then fine, if it looks worse, this is good – it means the stain is being drawn to the surface- just repeat the process.
It looks like you are in Aus? – you can get these product ( and some good advice) from http://www.aquamix.com.au
Hope that helps
Ian
Brian ROBINSON | Aug 9, 2011 | Reply
How can I remove White paint. From external slate windowsills.Blobs I can scrape off but most are smudges where attempts have been made to clean up.Beautiful material utterly spoilt.
Ian Taylor | Aug 16, 2011 | Reply
Hi Brian,
Really you need a paint stripper, I would suggest one deisgned for use on stone like Sealer & Coating remover, leave it dwell for a while then scrub off. You could also add a little nanoscrub or a poultice powder to help absorb it off once it has been cheimcally disolved. Make sure to rinse well after wards.
Hope that helps
Ian
Denise Bridge | Aug 25, 2011 | Reply
Hi,
I was wondering if you could help me. We’ve currently got natural grey slate in our kitchen. Unfortunately, there has been some paint spilt on the kitchen floor but some of of it has been removed but it still looks very dull and lost its sheen.
I read the comment above but I am still worried that our slate floor is porous and will stain the slate rather than clean it.
I was wondering if you can recommend me a product that will remove the thin layer of paint that has been left on the slate.
Thanks,
Denise
Lew | Aug 28, 2011 | Reply
I have a slate stone patio and a walkway entrance leading to the front of my house. It is dirty and uneven in its color. What can I clean it with and what solution can I seal it with. How often do I need to put a sealer on it. Also, there are some paint marks and oil stains on it, too. I appreciate any advice that you can give me.
Ian Taylor | Aug 30, 2011 | Reply
Hi Lew,
OK, for an external deep-clean I would use a high powered Alkaline cleaner that is designed for stone.
If it is a large area I would borrow or hire a rotary cleaner with a medium nylon brush head. If the slart is very absorbant, pre-wet the floor with water, then apply your mixed cleaning solution and leave it to dwell for 15 minutes or longer, (keeping it wet though, with more cleaner). Then scrub with the machine, really work the brush into the uneven parts of the slate and don’t forget to work on the joints.
Now rinse – with plenty of clean, fresh water, a wet vac may not be practical outside with uneven floors, so maybe you can use a hose or pressure washer to rinse away the now dirty cleaning solution, go over the floor again with the scrub brush while rinsiing also to make sure you get all residue up and off the floor.
Once you have done this, the floor should be a whole lot cleaner, and you may find that much of the paint splashes have come clean in any case, for any remaining spot stains like this, get a paint stripper, be careful and try to get one from a tile/stone shop desighed for the job (there are some slow acting, non-methyl chloride products that work great.) You can use any paint stripper but some, like turps and white spirit can leave an oily stain themselves.
When thourouthly dry (wait a few days – depending on where you are) you can seal it. You have a couple of choices. Usually a coating sealer (that leaves a nice sheen) is not an option outside – due to the harsher environment, they tend not to last too long and become too much of a chore to keep in good condition. So most people opt for a good quality impregnating sealer. They won’t give a sheen but but will leave a natural finish, you can choose between a natural or colour enhancning version which would bring out the colours but not add a coating or shine.
Hope this helps
Ian
Ian Taylor | Aug 30, 2011 | Reply
Hi Denise,
a lot of slate problems this week -
OK, you need a good stripper I suggest sealr an coating remover, no longer being brought intot he UK but there are still ample stocks at All For Stone – see ad link – suggest you give them a call they can also advise you how to use it.
Hope this helps
Ian
Marc | Sep 14, 2011 | Reply
Hi Ian,
I am so pleased to have come across your article and am looking for some advice regarding our honed slate hearth.
One of the kids spilt their cup of milk over much of the hearth, and we didn’t know about it until the next day. We found to our horror after wiping it up that we are left with the staines!
Can you offer us any hope or advice?
Regards,
Marc
Ian Taylor | Sep 20, 2011 | Reply
Hi Marc,
This may not be too difficult, it depends on the slate, but most hearths are typically from good quality, quite dense slate, especially if they are honed. So, I am assuming that your slate is not too porous. This means that you may only have surface stains. Milk will leave fatty/oily stains and so you need to try an alkaline degreaser. First pre wet the area with warm water, then mix an alkaline cleaner with warm water and add it to the staine, allow it to dwell for about 15 minutes (don’t let it dry out) then scrub with a white nylon scrub pad.
Wipe up the cleaning solution, then rinse with clean water, wipe up and dry with a towel.
I this does not work, try a poultice
Kind regards
Ian
linda | Jan 2, 2012 | Reply
Hi
A couple of years ago my husband laid a natural slate floor in our kitchen it looked lovely – but then he sealed it with wood sealer I’m really not sure why. The result is we now have a horrid grimey brownish coating to the tiles. The floor is very difficult to clean, takes lots of effort and really dosent look any cleaner.Please help.
Linda
Ian Taylor | Jan 6, 2012 | Reply
Hi Linda,
OK, thse types of sealer are more like a varnish and don’t breath properly in general. after a while they get grubby and can even peel. They can also harden, and go dark or yellow/broan in colour as they age. My only suggestion would be to strip it off and start again. They can be quite tough to remove, needing a strong stripper and more than one application. I would suggest trying something like Sealer and Coating Remover which you can get from All For Stone (see ad on right).
see the stripping a coting sealer post on the blog.
I think that you may be pleasantly suprised at what is beneath the varnish, when clean and dry consider using a product like Seal & Finish Low Sheen – low maintenance coating sealer, will give a slight sheen and will need topping up in due course but much nicer to care for than the type pf sealer you have at the moment.
hope that helps
Ian
Wally | Jan 21, 2012 | Reply
Hello. Can you help us, we had a Brazilian slate floor laid it was grouted before they sealed it. And it never looks clean after washing paw prints etc never goes away I can we rectify this.
Thank you.
Ian Taylor | Jan 23, 2012 | Reply
Hi Wally,
You are going to have to go back to the surface of the slate. If it has been sealed with a topical or coating sealer (which is now over the grout residue) then you will first need to strip that back with something like Sealer and coating sealer or equivalent.
Then, if there is still some grout residie (it may come off as a result of the stripping opperation if you are lucky) you will need a phosphoric acid based cleaner to remove the grout residue, and this may take several goes. Do not be tempted to try to speed this up by going for a brick acid – that can and often does, create more problems than it creates.
Hope this helps
Ian
Carole | Jan 31, 2012 | Reply
Hi Ian,
I am hoping you can help. We have a smooth (not riven) slate in our kitchen and hall. It has not been looked after very well and I am pretty sure the majority of the seal has come off, we have certainly never done anything with it in 8 years so you can imagine it is a bit of a state.
So far I have scrubbed it with a nylon scourer using a slate cleaner. It is looking much better but there are parts that look like they have a sort of white haze on them which I can’t get off it seems to be at the edges, is this the old sealant do you think? I have no idea what was used to originally seal the tiles, I am loath to reseal without getting the floor totally clean. Many thanks.
Ian Taylor | Feb 6, 2012 | Reply
Hi Carole,
OK, the white at the edges could be one of 3 things:
Salt efflorescence – mineral deposits from the grout and or subfloor, grout is porous, the slate is not very porous, so any moisture trying to get out of the system, will come through the grout, not the slate, as moiture comes out of the grout, any disolved minerals that may be in the moisture will be brought to the surface where they will re form as crystals. If this is the case, it would temprarily disapear, or face at least when wet, only to become visible again when dry- a simple test, if you think you have this, a very mild phosphoric based acid cleaner, diluted with water, (nothing stronger like brick acid) will help.
Grut residue – ot could be the remnants of uncleaned grout residue from the installation, if it appears to have got worse recently, then the above is more likely, if it has be there unchanged for years then it could be grout residue. – Again same traement as above, mild acid clean.
It could also, as per your suggeetion, be the last traces of a topical sealer, but I would expect to see traces in other areas, like in crevices in the stone face, not just at the edges, even a non-riven slate may have some unduations and so some low spots that would protect the sealer from wear. It it was a sealer residue you would need a stripper to remove it.
Hope this helps
Ian
Martin Joyce | Mar 6, 2012 | Reply
Hey Ian,
You seem to know your stuff regarding slate and stones, so maybe you would help me repair a stupid mistake I made. I sprayed my new smooth slate hearth, which isnt sealed, with cilit bang (non bleach) which contains formic and sulphamic acids. I’m left with horrible white patches all over where the spray hit. I’m thinking a strong alkaline cleaner and was wondering if lemon or vinegar with baking soda would be strong enough to do this or can you recommend a good propietary product and application method? Thanks, Martin.
Ian Taylor | Mar 8, 2012 | Reply
Hi Martin,
OK, first of all, I am surprised that the acidic Cillit Bang has damaged the smooth slate, most slates sold for hearths are pretty old, grey, high quality types that tend not to be acid sensitive, so I would check that there is no film (cement, or other coating) on your slate that has been damaged by the cleaner. Or the cleaner could have dissolved some kind of contaminant and left a residue of that
However, some slates can be sensitive to some acids and so it is not out of the question that you have some etching. IF this is the case, then you may be able to desguise it or mask it with a wax type coating, or an enhancing sealer (you do say that the sate has not been sealed with anything else, so an enhancer might well work). But, you will probably not be able to fix it without re honing the surface and that may require professional help.
If it is acid etching, then the damage is done, trying to neutralise it now is pointless. Besides, vinegar and lemon juice are both acidic in any case, and mix either one of those with bicarbonate of soda, which is alkaline, and all you will do is create a spectacular bubble fest as the two react quite violently) it probably won’t harm the stone as the two things will fight each other and neutraliswe themselves but it won’t help much either and you will be left with the aftermath of the reaction – a hearth covered in a salt residue.
I would try some Microscub with a little water, if it is some kind of deposit from the cleaning product, this may help remove it. If it is etching, then it will do nothing but worth a try first in my opinion.
Hope this helps
Ian
butch | Mar 14, 2012 | Reply
hello! so wondering, based on some feedback, if i made a horrible choice by installing black slate for my shower and bathroom floor. i’ve been told it will be harder to clean then the white on white penny tile/grout that i had to replace due to the poorly installed cracking grout. am i going to hate this more then the filthy looking white tile/grout i had to rip out?? help! and what can i do besides sealing it? and is there a number one sealer you would recommend??
thanks!!
-butch
Ian Taylor | Mar 16, 2012 | Reply
Hi Butch, I must admit, I am not 100% sure what you mean by ‘white on white penny tile grout’
If you are asking, will a slate wal and floor be harder to keep clean than a glazed white tile, then yes, it could be, but should not be a major problem.
Sealing the slate is recommended as it will make the surface of the slate easier to keep clean. However, keeping the grout clean and like new has more to do with good management of the moisture in the shower area. A sealer will help keep contaminants at the surface, of both the grout and the stone, go for a good premium imprgnating sealer. THis will help reduce the amount of moisture able to get into the grout. ON top of this clean the tiles and grout reularly and also dry them down periodically, like once a week for sure. Doing this will keep moisture and contamination under control.
Not sure if I answered your question so let me know if not
Ian
Alme | Apr 19, 2012 | Reply
Hi Ian I really hope you can help me. We have slate tiles outside and also around our swimming pool. On the tiles we have spots it looks like some of the layers of the tiles have come off. I dont know if it is caused by rain. we live in South Africa in Pretoria so we do get alot of rain. I have considered removing the tiles as it really does not look nice. Have you any suggestions plese.
Ian Taylor | Apr 19, 2012 | Reply
Hi Alme,
This ‘flaking’ of some slates is perfectly normal, and should settle down after a while (once all the loose/friable material has come away). Slates come in all sorts of colours, and in many viarieties also, some much younger (geologically speaking) than others. Slates are metamorphic rocks, that means they ‘were’ somthing else before being changed (morphed) into slate. Basically most slates began as a sedimentary rock, laid down in layers (this layering of deposits is important in the formation of layers that can later flake away) of fine-grained materieral like clay, silt and mud etc. These sedimenatary rocks are then subjected to pressure and heat are compressed toghether. This compression, and folding and heat can cause things to break-down and or fuse, and also change and some minerals form cyrstals . This process takes time, lots of it, the longer the time taken (the older the slate) the less likely it will be flakey and have loose layers at the surface. Some of the more colourful slates I have seen coming from Africa can be quite flaky. Unless your slate is really friable, and almost more like a shale or mudstone than a slate, then once the loose parts have come away you should see the stone settle down.
If it is rain water causing the delamination, then I would think the the stone is very soft and have easily split cleavage planes, the expansion and contraction of the slate as it gets wet, and dries out etc, along with extreme changes in temperature could have an ongoing weakening effect. Sealing the slates with a waterrepelling sealer will definatley help but it may not stop it altogether,
My gut feeling is that if you cut-out the worst ones and replace (if they are that bad) and clean and seal them, you should see less of this happening.
Hope his helps
Ian