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.
Hi Trish,
It sounds to me as if the dark marks are perhaps the oily fuel from the logs or they could be the burnt residue of that, or burnt residue of sap from the logs. I doubt that the slate (if that is what the stone is) itself has been permanently damaged, but the sooty colour could have got quite deep into the texture and maybe fused it self to the stone.
If a mild neutral detergent did nothing, next on my list would be a strong alkalie but even that may not work. You may need to try a solvent based cleaner/stripper.
You could try something like Sealer & Coating Remover (you can get this from All for Stone – see link on side for number) this is a safe-solvent type cleaner, it needs to be left on the stone for some time, at least 30 monites before scrubbing. You could also try adding a little abbrasive cleaner – such as Microscrub (again, All for Stone) don’t add this until the dwell time is up, just before you start to scrub. The combination of the stripper working on any resin type stain with the mild abrasive and nanotechnology of the Microscrub may sort it out.
If that does not work, then try a more harsh abrasive, such as a honing powder, added in place of the Microscrub
Last resort would be a product called Extreme – by Aqua Mix – it is no longer being brought into the UK as the company has withdrawn all its products from Europe, but All For Stone have stocks. Extreme is a buffered acid cleaner. It can work well on carbon type deposits with minimal or no damage to the stone. As I do not know the exact type of slate you have I cannot advise this completely free of reservation, at the very least, a small test in an inconspicuous area would be required (as it should for any treatment)
Hope this helps, if you need more information please come back to me.
All For stone can advise you on a sealer also, feel frre to send them this answer as background
Ian
Hi Steve,
Any idea what type of slate it is? Slate is one of those stones that has a huge variety in terms of it’s geological age and make up. The ‘old’ slates tend to be darker in colour, stronger, have a higher clay content and less, if any, calcium-type compounds in them (making them less susceptible to acid etching). For this reason, it is this type of slate that is most often used for work tops – Welsh Slate would be a good example.
However, some younger slates (for example, some stone from India, Africa and China, can be aguably more accurately described by geologists as shale, or siltstone or similar, or slate that has only just become slate, relatiively speaking of course) can contain many more minerals, like Iron bearing minerals that are responsible for the rusty brown colours in many ‘slates’. Some of these slates can contain some degree of calcium-based mineral, or other acid-sensitive compunds. If your friend’s slate has etched then there is some thing like this in it’s make up.
If it has been etched then all may not be lost. As it is a work top, I am assuming it is a fine-honed surface (so very flat and smooth, almost polished?).
You don’t say if the slate had been previously sealed, if it has not then treating it with an enhancing sealer may disguise the problem, but you would have to treat the entire stone the same and if they don’t like the darker look that may not be an option.
If it was sealed, then an enhancing sealer will not penetrate and work. In this case (previously sealed stone) there is a very small chance that applying an enhancing sealer just to the etch mark may help, but I cannot guarantee it. You could try dabbing a little oilve oil over the etched part, rub it in and see what it looks like. If it ‘fixes’ the damage without darkening the surrounding slate, then that is a good indicator that an enhancing sealer will do the same, (of course the oil will wash out). Use an alkaline cleaner to rinse out the oil and try an enhancer.
One other possibility; some impregnating sealers are acid sensitive themselves: if the slate had been sealed with such a sealer, these are often solvent based, they themselves can darken the slate a bit, the owner may not know as this is how the slate was presented to them. But the acid from th leemon juice may have done nothing to the slate itself, but damaged the sealer and the white markes are the ‘damaged’ sealer still remaining. For this you could try localised stripping of the sealer (may have to do the whole slab though) using a sealer remover – try to find out what product was used and seek their adivce as to the best product to remove it. then when removed, re seal.
Last resort would be to call in a stone restoration company such as Marbllelife Ltd and get a quote for resurfaceing the stone – this involves diamond grinding and re-honing (like planing and sanding wood to get rid of scratches with progressivley finer grades of paper until you get back to the smooth finish.)
Hope this helps
Ian
Hi, I have just had a Welsh slate floor laid in the kitchen.
It has been sealed and grouted and I was led to beleive
that all I had to do to clean the residue (from the grout) was use a mop
and water. I have tried this as well as using a sponge and drying
the slates straight away with a towel , however the grey wipe marks
keep returning. Any advice on what I could try? I’m a little
nervous as the floor was rather expensive!
Many thanks
Hi Llinos,
OK, whoever told you that you could just mop the grout residue was not being truthful, dried on grout residue is not easy to remove at the best of times but on slate it can be really tough. If your slate is riven, and the residue is caught in soe of the crevises then it is even harder. If you r slate is honed (or fine rubbed as Welsh Slate describe it) then it will be easier.
OK, you could try just a cream abrasive, such as Microscrub – put a little water on the slate, then add a small half cup of microscrub, and use a white nylon emulsifying pad . This is abrasive enough to rub depostits away without damaging the slate.
Failing that you will have to use a mild phosphoric-based acid cleaner – or similar DO NOT USE A BRICK ACID. Pre wet the floor, add dilute acid cleaner (follow on bottle instructions) and scrub. Then pick up the solution with a mop or wet vac. then, and this is important, with both methods, rinse with fresh water, pick up the rinse water, then rub the floor dry. And in the best traditions of hair-cair – repeat if required.
Hope this helps
Ian
Have slate at back door. Footprints are showing due to cream that was on someones feet. Any suggestions on what to use to remove would be very helpful. Thank you.
HI Sandra, I take it you mean cream as in the dairy stuff?
If so a deep clean with an alkaline cleaner like this should help.
If it has stained the slate then you could try a microabrasive cleaner like microscrub or even a poultice.
Hope this helps
Ian
Hi Ian.
You are obviously very knowledgeable and have helped many people! Thanks for that.
I have a black slate floor that has had an area rug laid across a large portion for many years. When I pulled it up, you can see the lines from the bottom of the carpet. I have scrubbed the floor with water and a mild detergent twice, but those carpet lines are still very evident. Is this permanent damage or can it be cleaned? What is the best way to clean it? I thought it was just residue from the dry-rotting carpet, but it just will not clean.
Thanks so much!
Anita
Hi Anita
If you could look at the surface of your slate under a microscop wou would see a tiny micro-texture and I suspect that the carpet backking, (not sure what type it is) has over the years been rubbed well and truly into this texture. As these tiny pores in the surface are microscopic, a detergent may just float over the top. You could try scrubbing more vigorously but also, try to get hod of a product that contains a mild abrasive. If yyou are in teh USA, look for Nanoscrub by Aqua Mix. this might just help get into the testure, its particle size is small enough and also the nanotechnology will help to allow the liquid part of the cleaner better access
If the backing of the carpet was rubber or some other resinous type base, you may find that a solvetn stripper of some kind is helpful in breaking it down. You mmay need to experiment with these two approaches.
Hope this helps
Ian
Thank you! I scrubbed with a brush and baking soda, and that helped. But it didn’t clean it entirely. I suspect I need to repeat, or better yet, get ahold of this product you have described. Thank you so much for your help and quick response!
Anita
Hi Ian,
Just been reading through your messages and this is a great blog. Thanks! I’ve absorbed all that you’ve said above but am uncertain whether it applies to my situation. I have a black slate bathroom/wetroom. It was installed five years ago and has a slightly uneven surface. After a shower, the water therefore pools in one quarter of the shower floor and drains very slowly over the day. Obviously over the years there has been a pale build up of limescale. I bought some HG Professional Limescale Cleaner and have given the shower several scrubs/rinses with that. The troublesome slates are a bit darker now and look ‘cleaner’ but now I have very visible white patches in the grout. They are not small and I’m panicing! Should I apply more of the product? Its still fizzing when I put on the product so somethings happening but I have a nasty feeling I might be making it worse! I’m almost tempted to get a heavy duty marker pen and black out the grout! Any help would be hugely appreciated.
Thank you!
Mike
Hi Mike,
OK, the limescale remover is based on an acid, I cannot say which as you do not give me the actual product name (I think HG have more than one). Acids will remove the limescale and soap scum. They do this by reacting with the akaline residue, this lifts the limescale, revealing the slate underor haze neath, so now you can see the natural colour of the slate, without looking through the thin cloudy ‘veil’ or haze of translucent limescale. So that is all well and good.
However, when an acid is put on grout, it will also react with the alkaline cement in the grout, dissolving it. The acid-alkaline reaction happens until they neutralise each other, or one or other of them is all used up, the reaction creates two by-products, water and a salt – this is visible as the effective ‘whitening’ of the cement – in other words some of the cement, that reacts with the acid cleaner, will be changed into a salt and this is the white blotchiness you can see. Also, as the reaction dissolves some cement, it is removing it, we call this etching, so it will open up and roughen the surface of the grout – like a fine chemical peel and this too alters the look of the grout as when dry, the light will be scattered more by the relatively rough surface of the etched grout than by the smooth un-etched surface. – no doubt when wet it looks much better?
over time the whiteness will subdue as the roguh edges get worn down and fill up you could also consider using an enhancing sealer to darken them down again – so make the effect of water, a permanent one.
Hope this helps
Ian
Hi, I have just relaid a dark grey slate floor. I’ve cleaned the floor afterwards with Heavy Duty Slate Cleaner (from B&Q) and this has removed all the grout marks but a number of the tiles are left with marks. These can be mostly scraped off so are just sitting on the surface of the tile, but there are too many to do all this way, and some of the marks are too difficult to remove.
I think this is tile adhesive left on the tile after laying although i could be wrong. Do you have any suggestions on how to remove this?
Thanks
Ewan
Thanks so much for your help and wise words, Ian! I think I understand the proces but do I continue then until I have ‘neutralised’ the alkaline in the cement? Its only random patches of the grout not all of it. They seem more pronounced though the more I pour on the limescale remover. Shall I try the HG Grout cleaner instead? Or a combination of the two?
My HG product is literally called ‘HG Professional Limescale Cleaner’ See at http://uk.hg.eu/products/show/id/492/professional_limescale_remover__hagesan_blue___0_5___1_l_
Highly concentrated acid cleaner. S.G. : ± 1.13 g/ml pH : ± 1.0 Usage : 20 – 40 m² per litre Active matter : 34% Components : phosphoric acid, sequestering agents, nonionics, solvents, alcohol, oxalic acid, gluconic acid, perfume and water
Thanks!
Mike
Hi Mike, I would not conintue, every time you do this technically you are damaging the grout, albeit in a minescule way. If you are thinking, that you can even out the effect by uniformly etching the entire grout, that is a reasonable idea but in prcatice the distribution of cement may not be that uniform, or there may be concetrations of polymers in parts of the grout that inhibit the reaction so you may never get a patch-free look. The Product you used is mild, and safe enough, but it is still an acid and all acids etch.
Instead I would investigate using an enhancing sealer to darken the grout down
Hope this helps
Ian
Hi Ewan, you probably have a combination of stubborn grout marks and maybe even some tile adhesive. Don’t know the B&Q product but if it is acid based it will have helped by remving a thin film of grout haze, but, it has to be a safe acid that works on thin layers at a time, so if you have thicker layers, or lumps of adhesive – it may take several applications (each time also etching the grout in the joints by the way.
At the end of the day, there is no magical formula for removing this, if the grout/adhsive was heavily poymer modified then a solvent may help, but all that will do is soften the polymer, and not the cement. Either way, applying your cleaner several times, each time scrubbing hard and maybe using a plastic scraper on the stubborn parts, may be all you can do
Hope this helps
Ian
Hi Ian, many thanks. In the end, using the acidic cleaning solution neat (having tested it on a spare tile first!) and scrubbing very hard did the trick. The tiles look good now.
Cheers
Ewan
Have just found massive slate slabs (about 1m by 0.75m) under the carpet of our 170 year old house. Have had them cleaned and sealed. Biggest problem is deterioration of the slabs at their edges (defoliation?). Do you have any idea if there is a product that might “glue” the deteriorating edges and so prevent further breakdown. Thanks for any suggestions.
Ian,
We appreciate you advice, but are still puzzling over the gold markings on our black slate purchased in the US. We are fairly certain they are not rust because there is no water source nearby and the stains don’t look like the examples of rust on slate that we’ve found on the internet. The markings, which appear on only a handful of tiles, look and feel like clusters of metal shavings (or small rectangular crystals) and are bright gold in color. The material is very hard and firmly adhered (embedded?) to the surface of the stone. Wish I could attach a photo to illustrate. If it’s a mineral deposit, do you have any idea what it could be and whether it is typical in slate? Tile supplier says they have never seen it before. Tile installer says it’s part of stone and cannot be removed with cleaning. We were shown several sample pieces prior to making the purchase, but of course none of them had the slightest hint of gold on them.
Hi Ian,
We just refinished our shower with a dark slate threshold and I went to clean it for the first time and didn’t think about what cleaner I was using. I used a Mr. Clean product and now it is left with significant white porous stains. Is there anyway I can now get rid of this?
Thanks
Hi Geoff,
I am struggling to think of a product that may do what you are suggesting. there is one idea I have, and I am thinking out loud here, not tried this but:
Using a VERY dilute pva (like unibond)or better still an SBR (like Bal Bond) – has to be very watered down, you could try letting some solution of this soak into the grout joints, and hope it will soak in laterally also to the slate edges. Rub it dry so it does not dry on the surface. Let it dry overnight. I have successfully re-bonded loose screeds to concrete bases using this method.
However obviously you would need to strip back the sealer on both the tlate and the grout in order to do this – but you could do a small test area.
Hope this helps
Ian
Hi Liz,
OK, what you are describing does not sound like rust (iron oxide) – Although I have to say that the slate does not need to be near a source of water, the iron-bearing mineral can lay deep inside the slate, then when the slate is split (to produce the tiles) it is exposed to the atmosphere and the moisture in that alone can be enough, not to mention the moisture involved in fixing and grouting, then washing – all that can be enough.
However, you describe small gold, rectangular crystals, this is almost certainly Iron Pyrites – quite common in slate and yes, an absolutely naturally occurring phenominum. Think of it like knots in wood – perfectly natural, I would ask the supplier to just change the few tiles affected as the sample set they showed you had no indication of these natural markings (if you were buying knotty pine the samples would be knotty also, if you wanted pine or other wood free of knots and the samples you saw at purchase were all free of such marks and uniform in appearance, you would put any knotty pieces to one side, use as cuts etc, or, if you have a large proportion of them, take them back).
You will not be able to remove the crystals without physically digging them out, and that will leave a hole and damage the slate.
If you google ‘iron pyrites in slate’ in images you will see quite a few:
https://www.google.com/search?q=iron+pyrites+in+slate&um=1&ie=UTF-8&hl=en&tbm=isch&source=og&sa=N&tab=wi&ei=7C2NT574Gcek0QXOo_yDDQ&biw=1280&bih=604&sei=7i2NT_TlBsbJ0QW2-4H8DA
Hope this helps
Ian
Hi Kirsty,
I am not familiar with that product here in the UK, (I have no idea if it is basically basic/alkaline, acidic, or solvent) but it could be that you have done one of several things:
1. if acidic it could have damaged some of the grout, and left a fine film deposit of from the cement on the surface – another clean with a very dilute acidic cleaner follwod by plentiful rinsing with fresh water and towelling dry may help
2. Again, if the cleaner is acidic, it may be that you had a grout haze on the slate that was not that noticeble and you have now partially removed it, making it look temporarily worse – again try repeating the above process in a small area
3. if solvent or alkaline and you have a sealer of come kind on the slate, you may have partially stripped the sealer, leaving damaged sealer behind – you would have to strip and start again if this were the case.
4. maybe just a deposit left from the cleaner, due to not rinsing, – try the solution in # 1.
Just some ideas that come to mind
Hope they help
Ian
Hi Ian
We bought this house in Brisbane, Australia about 3 years ago and the previous owners had smoothed/ground down the slate and I am not sure what sealer they put over it.
The slate is very light almost white and is very cool in summer.
My problem is that something is staining the slate and leaving ugly grey marks on it. I think it is water as I have noticed that when water is left on it for a period of time, it stains it.
So my questions are:
1. How to remove these stains
2. For general cleaning, what can I use. Is a steamer ok or does that wreck the sealer?
Thanks in advance
Cheers
Emma
Hi Emma,
I am not sure of the type of your slate, most slates are darker in colour but it could be a slate. If you are getting marks just from water, then I don’t think there is much if any effective sealer left in the stone.
A good impregnating sealer will help, although you will stil get some surface wetting, the sealer will keep stains close to the top long enough for you to clean them. It is still important to react to stains right away, even with a sealer – all sealers do is buy you time.
The marks are left when contaminants disolved in the water are left behind when water dries out. A good deep clean should clean them.
I would suggest, as you are in Brisbane, that you contact http://www.aqua-seal.com.au Call my good friend A’nge and he can talk you through what you need. He can help identify your stone and the nature of the problem, then supply whatever cleaner and sealer you will need. Given the stone is marking so easily, and that you will be conductiong a a deep-clean, you are going to need to reseal in any case. A steam cleaner may help, I would still use a deep cleaner first, maybe use the steam cleaner to help you rinse.
Hope this helps
Ian
hi there,i installed a slate floor around a year ago,i put on a neutral sealer, the floor is brazilian blue/grey slate, ive had so much building work going on that the floor is really scratched all over, what would you recomend to strip it back?? also i want to seal it with a glossy/wet look sealer,any ideas would be greatfully recieved.many thanks rick
Dear Ian Taylor,
I have read lots of your previous comments going back to 2008, which I have found very useful! We have welsh riven slate tiles (of blue/grey colour) which were laid on the floor in our kitchen, dining/ family room area and continuing outside onto the patio. At the time we did not pay too much attention to getting the grout off or the sealant we used. We used Lithofin Slate Seal on the inside tiles and Thompson’s One Coat Patio & Block Paving Seal outside patio. We really liked the wet-look shine of the slate sealer when it was first done, albeit does show up the dust terribly! Fast forward almost 3 years and the slate is looking grubby, particularly in the kitchen area and is scuffed and scratched around the dinning table. I know from reading your previous advice to others that we need to use a Phosphoric based acid cleaner, lots of scrubbing with nylon brushes/ pads and plastic scraper, mop/vac up and rinse and dry in order to get muck, grout and any old sealer which may be left up. My questions are:
1. Could you recommend a particular cleaning product for this job?
2. Is the Lithofin Slate Seal a good quality product, or is there something better and more hard wearing we could use? Or should we be using a sealer which soaks into the tile instead?
3. Once we have fully cleaned and re sealed, what should the ongoing maintenance be to keep it looking good for longer? Eg dusting/vac floor mopping with only water?
4. How often should we be putting on sealant, can this be put straight on top of previous layers once cleaned up properly?
5. What do you suggest for the outside tiles?
Many thanks for your time,
Regards,
Adele Goodfellow
Hi Ian
My husband has just installed a new piece of welsh slate for the hearth which has not been sealed. On delivery it was left outside the door on a wooden pallat and shrink wrapped. It has dark areas which look to me as though something has been spilt on it. My husband thinks that this is natural but I’m not convinced especially has there has been some mild improvement since cleaning with Liberon stone floor cleaner. After reading your blog, I’m just about to try cleaning with washing up liquid and warm water but do you have any other advice.
Hi further to my previous comment the darkened areas feel rough (we had asked for a flat finish or is that fine rubbed?)and slightly raised.
HI Rick,
OK, well with all that work I imagine that it is the slate that is scratched not just eh sealer. You can strip back the sealer with a standard sealer remover/stripper (such as Sealer & Adhesive Remover or equivalent – a solvent based product.). Rinse well and allow to dry completely.
When dry see if the scartaches are still an issue (you may find that the scrubbing and stripping priocess makes them acceptable). If the slate is honed then applying a wet look/sheen finish may not be possible. However if the slate has a natural riven fisnish then it ought to be OK. In the case of a riven finish I would recommend something like Seal & Finish Low Sheen. Try the link to All for Stone.
Hope this helps
Ian
Hi Adele, Lot of questons there I will try to answer them in the order in which they were asked:
First of all though, before you use an acidic cleaner (I assume you meant for the grout residue?) you will need to remove the remaining Lithofin Slate Seal. You will need a stripper for that, you could try Sealer & Coating Remover, or try whatever product Lithofin recommend for its removal. Then you can follow the advice for removeing any grout residue (although you may find some of it coming away as part of the stripping process)
OK, Q1. Oops, I hink I answered that above
Q2. Yes, to my knowledge it is a very good sealer. Is it the best? – hard to say. I can recommend an alternative in Seal & Finish Low Sheen (available via All for Stone) is it harder wearing than Lithofin- I don’t really know, maybe, perhaps just a bit, but the main differenence is it is water based and much nicer to apply. But they are both topical sealers and will therefore wear and so in a high traffic area they will need frequent reapplication, I think that the 3 years you have had the Lithfin on for is the very max limit for this type of sealer. You may be better reapplying every year.
Q3. You pretty much answered this yourself, keep grit off the floor (dust mats) sweep vacuum regularly, Mop up isolated spillages as teh occur, use a mild eutral cleaner for every day or routine washing. Avoid using harsh cleaners. Alkaline cleaners will remove some coating sealers or at least dull them severely.
Q4. As often as required. I cannot speak for the Lithofin product but the Seal and Finish Low Sheen can be applied to itself wiothout theneed for stripping back. As you are going to have to strip the floor anyway there should be no problem putting any coating sealer down.
Q5. For outside I would use a good impregnating sealer, the external environment is too harsh for a coating sealer.
hope this helps
Ian
Hi Jackie,
Sounds like stain of some kind, if washing up liquid does not help, try an alkaline cleaner, you could also try a poultice
hope this helps
Ian
Hi Jackie,
OK, it sounds as though you have got a riven finish – a natural finish where the slate is left as it is when it is split. This can be very smooth but with the occasional bump or it can be an all over texture. This variation oin the surface could well be naturally varied in colour also. It sounds to me as if you had wanted a fine rubbed (honed) finish – where the slate is ground to a very smmoth and flat surface. I would double check this with your supplier. You could still have patches of darker or ligher colour in it though.
Hope this helps
Ian
I have just laid a brazilian natural slate floor and it has been sealed with Lithofin.
My client is complaining that when you walk on it, you can see footprints from trainers. (It was sealed 4 weeks ago).
Is there anything I can do to stop this?
Many thanks
Steven
Hi Steven,
Unfortuantley you do not identify the actual Lithofin product. So, I do not even know if we are talking about a pentrating type sealer or a coating.
If a coating (like multi seal or slate seal) then you are leaving a top coat of sealer, it should not act as you have decribed, if it has, something is wrong, possibly that too much was applied, or the stone was too dense to recieve it in the frst place (smooth surface, non porous and/or presence of some previous sealer remaining – the latter unlikely in a new floor I admit) and this has preveneted it from drying correctly (it can skin and remain sticky). If this is the case, it will need stripping back and redoing (if it is possible to do it due to the density/porosity of the stone).
If a penetrating type sealerwas used, then again soemthing similar could have happened, in that too much can be applied, leaving a residue at the surface which is not supposed to be there (so you will leave foot prints) or (less likely I think) not enough has been appplied so the stone is not quite sealed enough.
hard to say from the infomration provided but hopefully I have given you some things to investigate
Hope it helps
Ian
We have a green slate floor in the shower and around bath and sink. It is sealed, but our water leaves white marks on it. It is well water with a water treatment system and added calcite. The calcium is easy to clean on stainless steel and any other surface, but for some reason it seems like the slate has absorbed it. Once I tried vinegar to clean it on the slate, since this works in our kettle and dishwasher, but it made things worse as well as making the grey grout white. Sometimes I put mineral oil on the stains to hide them, this lasts a month and then they are visible again. We have purchased a special stripper and sealer that is apparently really good from the slate dealer. But wanted to see if there is anything else I can do before I go that route. We had sealed the tile really good when it was installed, even a few times; this problem started a month after sealing it. I don’t want to have to go through all this trouble, if the same thing will happen again. Plus we have a 5 month baby in our house and don’t want him exposed to the fumes of the stripper. Any suggestions on where to begin. I was thinking of using CLR, but worried it might make it worse. The stains seem like they are in the slate, not on the surface.
Hi Darlene,
I can see your dilema, I do not know CLR, but a quick look makes me think it is an acidic cleaner – so will have a similar effect to vinegar.
The issue you have is that any cleaner that will break down calcium will be acidic, and any acid will etch – hence the grey grout turning white.
Why there is only a problem on the slate? – well even a good impregnating sealer leaves the actual surface of the slate exposed, it could just be that the calcium bonds more easily to the surface of the slate through adsorption (as opposed to absorption).
The mineral oil could be simply masking the problem (and certainly helping to dampen down the white colour back to grey on the grout). But oil is transient, it won’t last, plus the calcium will just sit on top of it anyway.
You could try an enhacning sealer (does the same job as mineral oil but will be permananent) the only problem is it can be tricky to adequatley remove the exiting sealar, so as to allow the enhancer to get in evenly.
It might be possible to acid clean again, then use an enhancer just on the grout, then adopt a regime of prevention rather than cure. Use a mild abraisive cleaner such as nanoscrub (I think you can get this in Canada, it is an Aqua Mix Product) – using it frequently before there is build up, to lightly abraid the calcium away.
Hope this helps
Ian
Hi Ian
I’ve read lots of your advice to see if it would help me but am still not sure.
In 2008 I had a Burley flueless gas fire installed and a black polished slate hearth put in. Soon after (and again this week) water seeped in from the chimney flue and now there’s a greyish matt stain on the slate which I can’t shift with the special slate oil I use to clean the slate. The chimney is capped but not blocked and I fear this is going to happen again and again with all the rain we get in England! What can I do to remove the stain? Thanks for your help.
Hi Ian,
Thanks so much. You have a great blog and it helps so many people. I will try the nanoscrub first to see what kind of residue I can remove first. It sounds like a really good product. The enhancing sealer would be nice if it all works out, our tiles look so much richer with the mineral oil and will be great if we can get the same effect with the sealer.
Thanks again,
Darlene
Hi Marie-Hélène,
OK, I am assuming the slate was also sealed prior to the water getting through?
Even if not, the fact that the slate is polished and black tells me that it is likely to be a very dense slate. The special cleaing oil, is really just an oil that leaves behind a film that will to some small degree, penetrate and absorb, but also ‘adsorb’ – which just means bond to the surface, then you polish that by buffing – so this will have acted as a bit of a sealer. Using it to clean is a bit of a misnomer, really as it has had some oil already, as a sealer, not much is going to get in to the slate and so wiping away the dirt with more oil is in theory quite easy and at the same time you are keeping the oil topped up or refreshed.
This is fine but it will not prevent everything, some contaminants will land on top of the slate, (and on top pf the oil) and still manage to bond to the micro textrue of the slate. The marks you describe sound like mineral deposits: water is very ralrely pure, often there are minerals disolved in it. For example, there can be calcium carbonate or other soluble minerals. Also, as the water has seeped through the chimney, running accross bricks and cement, there are other things it can pick up including soot, but also more calclium from the mortar joints among other things.
The water carries them down and splashes on the slate, the water then evaporates and the minerals being carried get left behind, if they are minerals like caclium (from cement) they will re-form as a fine crystal layer and would be able to bond to the surface to the point where just wiping them with oil will not remeove them.
You could try rubbing with a white scouring /emulsifying pad. Or try a bit of Microscrub (a powerful abrasive cleaner that will not scatch the slate, or remove any oil that is already inside the slate – may remove some fromm the surface but that is easily replaced afterwards).
It could be worth checking that it is not acid etching – effectively from acid rain, or water that has become acidic because of what it has picked up along the way. I have to say, I am unsure what the ph of rain-water combined with chimney soot, but if it were acidic and if the slate is sensitive to acids, then you could have some acid etching – where the acidic contaminant actually corrodes the polished surface. Cleaing with oil would not solve this (although it would temporarly mask it, until the oil dries or fades).
If you can ascertain that the slate is in no-way affected by acids then that rules out etching, and also, it allows you to explre a mild acidic cleaning solution to the mineral deposits – in other words, provided your slate is not affected by acids, a mild acid based cleaner (like phosphoric acid cleaner, or some house hold cleaners that have citric acid, or even viengar for that matter) may help to remove the splash marks. BUT – please ascertain the acid sensitivity of your slate first- by calling the supplier, if they don’t know, ask them for an off-cut, a piece of watse so you can try lemon juice and other acids on it first.
Regarding this happening all the time, yes unfortunately it will, unless you can stop the water from getting in, but if you find a way to quickly remove it, and you keep the oil refreshed, it should be easily manageable.
Hope this helps
Ian
Hi Ian
Could you advise, I’ve recently installed a slate floor across my ground floor approx 190 sq meters. The floor is a chinese slate and has been installed on a sand/cement bed with a wet underfloor heating system.
The problem I have is cleaning the slate as there is a dusty residue that simply keeps drying when I mop the floor.
I have sealed part of the floor with feb superclear 181 but I think the floor was still damp as this “bloomed” went cloudy, so I cleaned it off with whitw spirit. I’m not sure what to do next could you recommend a cleaner (there is still some cement stains on the slate) baring in mind the area that needs cleaning, or a acid that will do the job.
With thanks
Jon
Hi Jon,
It is not unusual for this type of slate to be dusty when dry, much of it is a much softer slate than say, an indigenous UK slate (like Welsh Slate for example) so there can be some surface dust that will settle down over a short period of time. Also, if it is a multi-colour slate (reds, browns, gold etc) then much of that colour comes from minerals like Iron which has oxidized – so basically it is rust. This ‘rust’ and other oxides can be dusty.
Some of this rusty dust will wipe off with just plain water (and then more may develop) but some of it is going to need something stronger. Also, the remaining grout/cement residues will need a mild acidic cleaner – one made for the job, not and I repeat NOT a brick acid, based on HCL – way too strong and dangerous. HG Extra or Aqua Mix Phosphoric Acid Substitute are ideal, or there is another product called Extreme (also by Aqua Mix) that is slower to work, but will do less etching damage to the grout joints (all and any acid product will etch, and that means making darker grout joints turn much lighter although they will darken down again over time).
Aqua Mix is no longer being brought into the UK but there are some stocks left, you can contact Tilinglogistics Ltd on 0121 705 5333.
One other thing that I highly recommend you do is hire two bits of kit (given that you have 190 m2): A low RPM mono-brush cleaner with a medium hard brush head (low RPM means between 175 and 350). And a good wet vac – make sure the wet-vac has a good and new squeegee head, not one that has been used on over a thousand building sites.
Procedures may differ from product to product but for the Extreme (which I think I would suggest) it would be like this:
1. Mask off and protect any adjacent surface from contact with both the acidic cleaner and water.
2. Sweep or vacuum your floor to remove loose dust
3. PRE-wet the floor by mopping with clean water (allows proper wetting action of cleaner, prevents cleaner from diving too deep into stone, and keeps it active for longer)
4. Apply Extreme, diluted (read on bottle instructions) to a medium-to-weak solution
5. LEAVE TO DWELL for 30 minutes or longer – keep wet in the mean time
6. Agitate/scrub with the brush on the machine
7. Use the wet vac to pick up the solution
8. Apply fresh, clean water to the floor and agitate with the machine again – this is the rinsing phase and is essential for removing the dirt and traces of the cleaner
9. Pick up the rinse solution with the wet vac.
Note, if your mono brush machine has a liquid tank, you can use this to help disperse the cleaner, then again later to disperse the rinse water. Agitate lightly as you go, but do not skip the dwell time, come back and agitate again after the dwell time.
Allow the floor to thoroughly dry out – especially as there is a sand and cement screed bed.
A note on the underfloor heating system: For cleaning and sealing it is always best to leave this switched off for the duration, if you cannot turn it off, turn it down and keep the temperature constant. While actually having it on slightly after cleaning may help the floor dry out a little faster, it may also dry it too quickly while you are cleaning and want it to remain wet. More importantly, you need a cool, constant temperature (again preferably off) when sealing, until the sealer has cured.
So, sealing:, once the floor is clean and dry (and by dry I mean very dry, less than 5% moisture, and after all that cleaning there will be a lot of moisture in the floor to get rid of – so allow it a good few days) you can seal with your chosen sealer. I am not sure if you are looking for a penetrating sealer or a surface coating type, they both had pros and cons, one advantage of the coating types (like Seal & Finish Low Sheen) for example is that they will make cleaning easier, keep the dust better contained from the beginning and impart a low sheen satin finish that will bring some of the natural colours to the fore, without overly enhancing them. The down side is that they will need regular top-ups, depending on traffic, every 6 months to 3 years
Hope this helps
Ian
Hello. Have been reading all the post to find an answer to our question. Here is my problem: we just had a slate tile floor installed. The tile guy laid the slate, then put Enrich and Seal on the tile before he grouted the tile. He did not follow the directions on the bottles of Enrich and Seal which say to remove any extra sealer after 5 minutes. The tile felt slimey like soapscum. We were very disappointed in the final look of the tile. At the tile store we told them we wanted a shiney finish. The Enrich and Seal did bring out all the colors but there is no shine so we used a floor stripper which removed the soapscum feel but now we want a shiney finish. We bought TileLab Sealer and Finish / Gloss. It is a Water Base, Acrylic Polymer with Glycol Ether. As I said before we did use a stripper to remove the Enrich and Seal BUT water does still bead on the tile. Can we use this TileLab sealer on the natural slate now since it has been stripped? We are really wanting the glossy finish. Not real happy with the place that recommended the Enrich and Seal because it has no shine to the finish. Thank you so much for your help!
Debra
Hi Debra,
The removal/stripping process you have undertaken has only removed the excess sealer – in other words, it has taken away only the sealer that was left, incorrectly, on the surface. However, it has not taken the sealer out of the stone, as evidenced by the fact that the sealer still beads water.
The issue you have is this, that sealer is virtually impossible to remove once applied, and it is a really good product in terms of doing its job as a sealer. It is designed to help prevent liquids from penetrating the stone and to keep contaminants out or at least at the very surface. This means that water cannot get into the surface very easily so it sits up in a ‘bead’ or ball. The sealer has effectively massively increased the surface tension of the stone.
The product you have purchased will not, in my opinion, work on top of the Enrich n Seal. I am not 100% certain of the exact product, but as it is labelled an sealer and finish/gloss – it is likely to be a combined sealer/finish. Bear in mind that Tile Lab is a Custom Building Products Brand – and so is from the same sable as Aqua Mix (who make the Enrich n Seal) and I would imagine that it is very close to the Aqua Mix product that goes by a similar name. These types of products require some porosity and texture to bond and the Enrich n Seal will not be able to distinguish the new sealer from the general liquid contaminants it is designed to keep out – so it will repel the sealer, it will bead just like the water and so won’t lie flat, this means it will dry streaky, if it dries at all, and where it does dry, it just won’t bond so will walk off easily, and look a mess.
The only thing you could try is a top coat gloss (Aqua Mix make one called Floor Shine & Hardener) or a natural wax. the Floor Shine & Hardener is also water based acrylic gloss coat, however it is not designed to be a sealer also. It will still be a challenge to get it to adhere and lie flat, and I have to say, it may not be possible.
What you can try:
You cannot remove the Enrich n Seal, but you do need to try remove or reduce significantly, the high surface tension. One thing you can try is to use a white scrub pad and an alkaline cleaner and really give the floor a good scrub, mop up and then rinse. When it is dry, try a small application of the FS&H (or wax, same goes for that – but wax would become a labor of love, not as easy to maintain as the FS&H). If it lies flat (spreads out nice and evenly with no ‘pulling back’ into ribbons of liquid), then it stands a chance of drying nice with a good finish and bond. If is is still pulling back/beading as you try to apply it, take a new, clean scrub pad and rub it into the FS&H on the floor while is is still wet (as soon as you apply it and it beads) sometimes this will help it to ‘relax’ and flow flat, now use the paint pad or whatever you are using to apply the coating to feather it out.
If your test works out then you can take the risk of applying it to the whole floor.
If it does not, another strategy I have seen used is to let the floor be for a while, a few weeks or months, allow time for the natural traffic to begin to wear the high surface tension down a bit, then do the alkaline cleaner scrub and try again. This way the stone surface has become ever so slightly, naturally worn, along with the sealer, (as opposed to you just scrubbing the sealer if that makes sense) Sometimes this works quite well.
The stone will be fine in the mean time, as it is sealed with a very god product – it just means that you have t live with the lack of shine for a bit longer.
Hope this helps
Ian
Ian,
Thank you so much for the information even though it wasn’t what I wanted to hear. :O( Your explanation was much more clear than anything I have read or been told so far. Thank you for taking the time to answer and to explain it all to me. I should have done more research prior to the tile installion.
Many Thanks,
Debra
Ian,
I have black welsh slate which is sealed on my kitchen floor. I have tried to clean the floor with a new steam cleaner which has left white marks or residue on the tiles. I have immediately stopped using it and wished I and never started. Do you have any advice on what the cause might be and how I can restore the tiles ?
Thanks
Brian
I live in a 1700 sf house that is almost completely tiled in a dark grey textured slate tile with (aparently) light grout. We have a dog and a cat and we live in a desert (DIRT). What can I use to deep clean the tile that has high dirt activity and how do I go about cleaning it? Then, what do I do to not keep it as clean as possible?
Hi Brian,
I think that the sealer must be a coating type right? If so, I suspect that the steam cleaner has partially broken it down (the heat and water has delaminated the sealer, and made it go milky white and loose its shine). The good news is I strongly suspect that only the sealer is damaged, not the slate. You will need to completely strip the sealer now and reapply it. You may be able to get away with just stripping a section, up to a grout joint, or doorway or somthing.
Hope this helps
Ian
It depends on what the ‘dirt’ is. For a deep clean you typically need a high alkaline cleaner and that amount of sq ft I would definitely consider getting/hiring a rotary scrub brush and a wet vac.
IF the DIRT is mineral based, and really stubborn then (as you are in the US0 you could try a product by Aqua Mix called Extreme – it is an acid based cleaner that is great on red dust, rust and other similar issues. – so do not mix it with the high alkaline – I suggest try the alkaline route first, if no good try the Extreme.
Hope this helps
Ian
Ian,
Thank you very much for your advice, really appreciate it. We will do it asap and update your forum with the result.
regards
Brian