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 Ian we have laid a slate patio but have managed to spill brick acid on some of the new slabs. Can you please suggest a way we can make the spots less visible? Thanks.
Hi Amy,
Slate dishwasher?? – OK, obvious question, has the slate been treated with anything? Any kind of sealer or shine/gloss finish? What could be happening is that the bleach cleaner has damaged some kind of surface treatment, rather than the stone itself. Hopefully this is the case as you may well be able to repair that, if you can identify from the slate installer what was used. If the slate itself has bee damaged in some way, (I guess a strong bleach could in theory etch a slate if the slate was susceptible to that) then it could be much harder to achieve anything. It might be that the lines you see are ‘clean lines’ the surface of the slate could have some kind of build up, or patina of polish or just the fact that it has been the ‘exposed to the elements’ face of the stone for a long time. IF this is the case then, in theory cleaning the entire face of the slate in a similar fashion may make it uniform in appearance – I would want to rule out the first possibilities before embarking on this though.
Hope that helps
Ian
Hi Dee,
OK, brick acid (by which you mean hydrochloric /muriatic) can etch stone, even some slate, (depending on the particular mineral composition of the slate). If this has occurred then it is permanent, some of the slate itself has been removed, ‘etched’. Depending on the finish of the slate (rough, riven, smooth honed etc) you may be able to rub it with an appropriate fine emery paper and or diamond hand sanding pads to try to blend in the spotted areas.
Hope that helps
Ian
Thanks Ian, the surface of the slate doesn’t feel any different on the marked bits so I’m wondering if it is as you say that the acid has just taken the surface back to its original colour. I’ll try to get a photo when it stops raining and upload it
I have slate window Cilla that were painted when house was bought we have stripped the paint off but now need a nice finish linseed oil has been mentioned what do you suggest
Hi
Linseed oil will work, if you buy the commercially prepared boiled linseed oil – do you have a small piece of also somewhere you can try a little on first? The other option might be an enhancing sealer
Hope that helps
Ian
Hi,
I left a bottle containing bleach on my slate floor, and now it has left a perfect circle much lighter than the rest. Is this fixable?
Thanks!
Hi
OK, well most slate is pretty colour fast and I would not expect bleach to damage it. However there are many stones that are in the slate family commercially speaking (they have similar characteristics and are sold under the umbrella term of ‘slate’). Some of these may have a tendency to be susceptible to damage from bleach; if they have any fine particles that may be affected by the beach. The other possibility is that there is some kind of treatment in or on the slate and it is this that been affected by the bleach (like a slate oil or sealer of some kind, which may have been on the slate without your knowledge). The end result is the same though something, whatever it is, has been removed, or altered (etched) and this has left a light ring.
There are possibly 2 ways to help here, either refinish the stone for example if the slate surface is polished/fine-honed etc then re-honing it with diamond pads may help (in much the same way that a scratch could be taken out of wood by sanding it, first with a more coarse grade paper then moving up through one or more finder grades until the same finish is achieved.
Or, if you knew what was in or on the slate then sometimes reapplying it may help – so a bit more slate oil if that had been used for example.
There is a chance that a good clean may help – if the white ring is ingrained dirt that has become etched, it might in theory be possible to remove that with a good deep / alkaline cleaner and with it the white ring – however I think this is less likely and I would do a very small test first in an inconspicuous area, I case it has a similar t=result to the bleach.
Hope that helps
Ian
We have slate tiles in the bathroom and shower, the shower tiles always have white water stain, even after cleaning, can you suggest a cleaner that will remove the marks.
Hello,
We recently had a patio layed and in hindsight now we were not very careful when we put the steps down with the cement and sand. I cleaned the patio as soon as the steps were laid but we are now left with a light grey hue covering the lovely slate. When i wet the patio the lovely slate colour returns bit as it dries it becomes pale again. I don’t know what to to and how to rectify it or what chemicals i need to buy if any.
I would really appreciate your input.
Catharina
Hi
I may have answered this my mail while I was away? – But in case not:
OK you are talking about hard water deposits or similar. The usual method for this would be an acidic cleaner and that may be whatyou need. However, you could try an abrasive first; such as Microscrub -a mild, calcium derived abrasive cleaner that will help to remove fins coatings. This may well work if the white coatings are very fine. Faiing that look for a mild, safe cleaner based on phosphoric acid, such as Grout Haze Plus. Make sure there are no other surfaces which are acid sensitive that the cleaner may come into contact with.
Hope this helps
Ian
Hi Catherina,
OK, it sounds as though a mild acid wash will do the trick. Provided that:
1. The slate itself is not acid sensitive (most are not, but you can do a test in an inconspicuous area or on a spare piece first)
2. There is nothing else in the vicinity with which the cleaner may come into contact, which is acid sensitive (Like concrete or limestone for example)
3. Use a safe acid cleaner
4. That you have not used a very dark coloured/pigmented grout/mortar – using ANY type of acid will etch the grout a little and lighten it in shade.
Having carried out a test and satisfied yourselves that it is ok to use an acid:
Pre wet the patio – this keeps the cleaner up at the surface where it is needed and also helps protect the grout from etchig as much.
Dilute the acid cleaner as per the instructions (always try a very dilute solution first, and go stronger only if you need to)
Apply the mixed cleaner to a small area and allow it to dwell for a few minutes, then agitate with a nylon scrub brush, deck brush or even a rotary machine with a nylon brush head. Remove the cleaning solution with a wet vac or mop, or power hose away. Rinse with fresh clean water and remove. Allow it to dry in order to visually inspect it – if it has worked great, if it has worked partially, i.e lessened the effect, then repeat the process.
We have a suitable product here, others are available of course
Hope this helps
Ian
Hi
I have been asked to clean a heavily soiled riven slate kitchen floor. This is black and shiney in places after 11 years of heavy kitchen use. I believe the floor may have had some initial dressing but not a topical seal/polish. The lady would like the to look natural/non shiney after cleaning and resealing. A glossy finish will be straight forward but I can find very little that will leave it easy to maintain and remain in its natuarl state. What would you suggest.
Hi Phillip,
You have hit upon a common issue; that being that the only way to make it easy to maintain – as in easy to just wipe and mop requires a coating sealer (whether it is modern acrylic or old oil / oil and wax), coating sealers will make the floor shiny (to a greater or lesser degree, and they do fade quickly) plus they wear off and require far more frequent reapplication. A non-coating, on the other hand, will last longer, offer a natural look, but the actual surface of the stone will be exposed and not quite as easy to maintain as it would be with some kind of coating/polish (although a lot easier than with no sealing at all).
The 3rd way if you like is to use a non-coating, enhancing impregnator – a sealer that darkens and seals but is still below the surface leaving a matt, non-shiny surface. However, this can be tricky on old, previously treated floors.
Personally given the client’s stated requirement for a shine-free, natural look I would opt for a good impregnating sealer after your deep clean. Over time the floor will rebuild a patina and become easier to clean.
Hope this helps
Ian
Hi Ian,
I have an unfinished slate hearth surrounding my open fire. Unfortunately last night, a burning log managed to escape and I presume lay burning on the slate for a period of time (yes, the fire guard was in place! But it still managed to fall infront of it on the slate).
This has caused two problems. There is a brown/orange patch directly underneath where the log laid, I presumed caused by the heat.
Secondly, the log caused a nearby candle to melt. I’ve got the wax up using a hair dryer and paper towel. However, there is a a very dark wax dye stain on the light grey slate that I have no idea how to tackle! Can I use talc and household bleach and leave to dry/lift the dye?
Would love to get some advice before I make it worse!
Many thanks in advance,
Nathan
Hi Nathan,
OK, I don’t think the heat has damaged the slate directly, (slate is formed under great heat and pressure and is a pretty resilient stone). It is more likely to be resinous residues from the log, although it may prove very difficult to completely remove. You could try applying an alkaline cleaner and leaving it to dwell for some time to try to ‘soften’ and ‘get into’ the residue, then scrub, rinse and repeat.
As for the wax, sounds like you managed to wick away 99%of it. There are various ideas out there I saw one chemist suggesting using vegetable oil – he said it worked – but I cannot explain wahy. Failing that try some kind of spirits such as white spirit or methylated spirit and a bit of elbow grease, with a scrub pad., Keep absorbing the solution with a paper towel as you go, then rinse with water, buff dry and take a look – if you are making progress (lessening the stain) repeat the process.
Hope this helps
Ian
I have a cream slate floor and in the bathroom nail polish was spilled, we wiped it off immediately with nail polish remover, this made streaky marks. I then purchased Full acetone from the hardware shop and poured that on the area, rubbing it with a soft brush this seems to have reacted with the tile and is now white like a impenetrable film over the tiles. I have tried sugar soap and also white vinegar but it doesn’t break through the layer . Hope you can help ????
re Hi Karen,
OK usually nail varnish remover/acetone usually is fine on slate and it usualy flashes off really fast and leaves nothing behind. So, it seems to me that there is something on your slate tile, some kind of coating/ surface treatment which could be factory applied or applied during or subsequent to installation. It is this coating, whatever it may be, that I think is reacting to the acetone, rather than the tile/stone itself. The acetone is breaking down the ‘coating’ but it has only done it partially, and then it is not rinsed and so the partially broken down coating dries as the acetone evaporates. This creates the white film that you see – it is ‘damaged, left behind’, coating
You coud try reapplying more acetone to the area that is now white, sometimes a second or third pass will finish the job it started, – so apply, let it dwell for a moment, then agitate, then mop up the acetone with absorbent papwe towels, then imediately rinse with clean water and buff dry. See if after another one or two goes, you get back to a clean slate, with no white residue. If you do then it confirms my thoughts. The down side is that this means you have damaged the coating so you will have to try to repair that (if you want the slate to look as it did before). If you can find out what poduct was used (usually an acrylic type surface coating) they can be quite easy to apply, some may even allow you to just top up the slate locally, in the area you are repairing. Worst case you would have to strip the entire surface and then reapply fresh coats of the finish, to the floor. You would be better acquiring a proprietary coating and sealer stripper / remover if you need to do that.
Hope this helps
Ian
I have used an acid based brick cleaner to clean plaster stains off our new brick fireplace. Unfortunately some of the cleaner has spilt on the new black slate hearth and discoloured it. Can you help with ideas for trying to restore the slate to it’s original black ? Thanks
Hi Richard,
Most slate is usually acid safe but if it isn’t then the acid has etched the actual surface of the stone. This means that it has dissolved the fine particles at the surface. It could also be that some kind of coating or surface treatment (oil, wax, another type of sealer or polish) may have been removed, if so then reapplying whatever was on there may help.
IF the discoloured / lighter patch looks fine when it is wet then you could look at maybe an enhancing sealer, but you would have to know for sure that no other sealer or coating had ever been applied before).
Failing that try repairing the surface, if it is a fine-honed (almost polished) surface then some very fine emery /wet & dry paper with a little water may help.
Hope this helps
Ian
Hi Ian
Great expert advice on this blog. I have what I think is a Brazilian slate large table and benches in my garden. It’s gorgeous. Over the years it became mottled (black splodges) and quite rough with a build up of lichen, life and bird poo. I decided to have a go at cleaning it up. I have managed to power wash and scour the majority of these mottles off it with a lot of effort and the slate is now much more like its smooth pale green-grey original finish. However, there remain some black mottles, a couple of rust marks where a metal dish once stood, and an oily stain where a bottle of suntan cream was left.
Therefore I have two questions: how can I get rid of the oil and rust? and is there an easier way of getting rid of the poo/lichen mottles other than power washing and elbow grease?
Many thanks, Lesley
Hi Lesley
OK, you have three different types of stain there
Firstly, you are best with something like a phosphoric acid cleaner for the rust – you could look at our All for Stone Grout Haze Plus for that. The oil from the sun cream you could try a high alkaline cleaner (obviously these are separate operations to be done at separate times, don’t mix these two types of product). For the stubborn black spots, you might need a patio type cleaner based on Sodium hypochlorite (bleach). You could try some dilute bleach on those also. If you get a patio type cleaner like this, it may also work on the oil spots
Hope this helps
Ian
Hi there
I have a slate hearth that has been sealed with lithofin stain stop. I have since had the wood floor around the hearth stained and oiled, and unfortunately some of the stain has got on the hearth. Please could you suggest how to remove it?
Thanks
Hi,
First thing I would try is an alkaline degreaser, (hi pH cleaner). IF that does not work and the oil has hardened then you are going to need a stripper or a thinner like white spirit – but hopefully the sealer you used will have prevented the oil stain from getting a deep hold., so it should just be at the surface and easier to clean.
Hope that helps
Ian
Hi
I hope you can help me. I have slate work tops (Italian I think) I have sealed them with a slate floor sealer but now they have gone sticky. My question how can I get rid of the stickyness and what can I use to seal them that won’t go sticky.
Thanks in advance for any advice you can give.
Anthony
Hi,
OK, sticky = too much sealer has been applied, and then it has been on the surface.
You don’t state what sealer you have used but I am guessing it is either a solvent-based impregnator or a slate oil. Either way, the method to apply it is to apply it lightly, allow a few minutes for it to penetrate then wipe away any remaining sealer left on the surface, in other words, do not allow it to dry ‘on’ the surface. Also bear in mind that many slates are very dense and do not take up much sealer in the first place – so it is even more likely to result in a heavy residue.
The carrier fluid (e.g solvent) is now slowly evaporating and leaving behind too much sealer, where it is not wanted, i.e on the surface (it is intended to go below the surface). As this happens the sealer becomes sticky, it will dry eventually but then you will have an even worse issue.
The first thing to try is to go over the area again with more sealer – this tries to make use of the solvent/carrier that the sealer was kept in. As the sealer has not yet fully set there is a good chance this will help. Basically, you are re emulsifying the sealer – turning it back into a suspension, that you can now wipe away with absorbent paper towels. Buff it completely dry, leaving no trace of sheen or gloss, it should look matt, or however it looked prior to sealing.
The benefit of this method is that it will not remove any sealer form where it is meant to be, i.e inside the surface. So no re sealing will be necessary.
If that does not help, then you will have to strip it back, you could try an alkaline degreaser but may need a solvent-type stripper. YOu could contact the manufacturer of the sealer for their suggestions.
Hope this helps
Ian
Hi l have unsealed slate tiles on my kitchen walls they are rough finished. Behind the hob got stained with grease when my husband fried bacon it also marked above where potatoes were bolied in a pan. I have tried warm water and dish soapbut theres still a darker patch, any suggestions on how to remove the patch? Im worried l damage my tiles which l love.
Hi Apologies for late replay, I am not checking this as often as I should.
I suggest you just try a degreaser – should not harm the stiles. You need something like a high pH cleaner. If you can’t get one locally then we do have a great product called Xtreme Clean on the All for Stone website
Hope this helps
Ian
Hi Ian.
We’ve just had a new slate hearth laid down. While sealing it, I noticed the following patch: https://yourimageshare.com/ib/hyxKHQ6UB5. It is only about a centimetre big, but highly noticeable even from the other side of the room.
It is slightly indented into the surface of the slate and seems to be a shade lighter.
Have you any idea how best to bring it to the same colour as the rest of the slate or otherwise reduce its visual impact?
Many thanks!!
Hi,
OK, first question, are you 100% sure it is slate? Lots of materials are sold under an umbrella term of slate (same with granite and marble), but they are not always what they seem; most slate is quite insensitive to acidic materials but some materials that look like slate or are close to but not quit the same, may have some calcium or other acid sensitive mineral in their make up. The mark yo have looks like an acid etch (brick cleaner, lemon juice, coca cola, vinegar could all do this).
The other thing to check is whether there was some kind of treatment already applied to the stone surface, You say there is a slight indentation, well again this can be etching (as it physically eats away some fine particles at the surface) or, if the stone was a light grey colour and has had some factory-applied treatment to darken it, and this surface has somehow been struck and chipped (a thin layer of the stone comes off) revealing the untreated surface below.
It could be either
What happens if you wet the light coloured patch? does it darken quickly? If you have now sealed the stone then this may not happen.
If you have not yet sealed it, and it does darken when wet then you could try using an enhancing sealer. such as the one linked below. If this works you may as well seal the whole thing with it. IF, however you have already sealed the stone then an enhancer is not going to do anything and the only thing you can do really is look at getting the stone refinished – but this would be a job for a specialist with the right tools to rub it back and re create the brushed effect (much easier to do in a factory).
Granite & Slate Sealer & Enhancer
Hope that helps
Ian