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, for example, Grout Haze Plus . 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 such as Xtreme Clean 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 such as Seal Gold+ 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 Blog.co.uk, 2013. See copyright notice above.
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!!!!
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
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.
Ian
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.
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
Ian
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
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.
Ian
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.
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.
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?
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
Ian
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?
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
Ian
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,
Julia
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.
Ian
Hello,
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,
Emma
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?
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
Ian
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.
Ian
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
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
Ian
Ian
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.
Rupert
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
Ian
Ian
Thank you so much for your time and attention.
I shall follow your helpful instructions/advice precisely.
Regards
Rupert
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)
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
Ian
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
Rob
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
Ian
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.
P
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.
Ian
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.
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,
Chris
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
Ian
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
Ian
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
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
Rob
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.
Thanks
Lynette
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
Ian
Excellent!- thanks for letting us know
Ian
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
Ian.
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?
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
Ian
Ian,
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?
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
Ian
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
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
Ian
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
Nick
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?
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
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
Ian