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Tile and Stone Maintenance

Cleaning Slate – Expert Advice on Cleaning Slate and Slate Floors – Part 1

Cleaning slate isn’t too difficult. It’s vital, however,to know what kind of dirt or contaminant you are trying to remove before you can make a decision as to which cleaning product is best suitable.

Slate comes in many different colours and finishes. Some of these are smooth whereas others have a textured surface. Undoubtedly, slate is a very popular material for flooring right now.

Slate generally has good resistance to mild acids so this gives you a much wider choice of cleaning materials than you would have with more acid-sensitive stones like limestone or marble.

So, how do we go about cleaning our slate floor?

First, you need to check whether the contaminant is mineral based? e.g. grout staining, cement, rust or general dirt. If it is, you would be advised to use a mild acid cleaner such as one based on phosphoric acid. Beware though as any acid cleaner may etch the grout also.

In most other situations where you have, for example, general dirt and grime, wax, oil or a general build up of old polishes etc. I would recommend using a strong alkaline cleaner for periodic intensive cleaning. For everyday cleaning I’d recommend using a mild, neutral cleaner.

Here’s an Expert’s 6 – Step Guide to Cleaning Slate:

1. Ensure your slate is protected with a high quality sealer: either an impregnating sealer which will give you a natural look with a mat finish and below surface stain protection. Or, if you prefer the look of wet slate, in so far as the darker colours, but still want a natural, mat, no-sheen finish, then look a good quality enhancing sealer such as Enhance ‘N’ Seal. Alternatively you can use a coating sealer for a pleasant low sheen gloss which really helps any ongoing cleaning.

2. You must eliminate all grit – this is the major cause of all wear to slate floors. Ideally, place a dust mat both inside and outside the room which will help remove grit from shoes and prevent it from spreading to the slate floor.

3. Sweep and vacuum the slate floor regularly. This will also help remove grit from the surface of the floor.

4. Mop up and soak up isolated spillages as they happen. You shouldn’t leave strong contaminants such as coffee or wine to dwell on a slate floor.

5. Wash the slate regularly intervals using a mild, neutral cleaner. This will clean the slate but it won’t damage the stone, grout or the sealer used.

6. Less frequently, carry out a deep clean. For this, we recommend using a high alkaline cleaner. More in Part 2.

Update 22/01/13 – Check out this case study on cleaning slate




Copyright Ian Taylor and The Tile and Stone, 2013. See copyright notice above.


  1. Hi Ian – We moved into a house with a slate floor and a slate bench in the shower. It is really cloudy looking. I bought StoneTech soap scum remover, stone tech mold and mildew remover and sealant. I have used the soap scum and mold and mildew remover a couple of times. It still looks cloudy. Did I wait too long? Do I have to do it more times? Do I need to or can I seal it while it looks cloudy? There is also white “stuff” that I can’t scrub away with an OXO nylon brush on the grout. Any advise is appreciated.

    Thanks, Mindy

  2. Hi Mindy,

    OK, well the cloudy marks could be efflorescence or damaged sealer. Some sealers will go cloudy upon curing if there is too much moisture present in the stone at the time.

    If the cloudy haze ‘disappears’ when wet, only to reappear when dry then it can suggest efflorescence. If however, it stays visible through the water, then it might indicate a sealer or come kind of coating/deposit other than efflorescence.

    If the latter, then try a small amount of old fashioned nail varnish remover (the clear type with acetone). Just rub a little NVR on a cotton pad onto the affected area, see if it improves it, removes the haze. If it does, then this indicates that you need to get a sealer stripper.

    If not then eff is more likely, and for this you would need an acid based cleaner, not though one based on HCL/muriatic. Instead look for a proprietary grout haze remover based on phosphoric or similar.

    The white on the grout is also likely to be efflorescence

    I would certainly try to clean all white marks before sealing. Don’t forget to thoroughly rinse and allow to dry before attempting to seal also.

    Hope this helps


  3. I’ve recently bought a slate fire surround but it’s been painted in white gloss. What should I use to strip the paint off without ruining the slate?

  4. Hi, the slate should be fairly resilient to chemicals like paint strippers so I would try one of those. You could also try a hot pain gun – You might find you can use heat and or a plastic scraper to remove the bulk and a paint stripper to remove the residue that is left after. I doubt any harm will come to the slate.

    What I cannot say however is why the slate was painted in the first place, you may uncover something that is not in great condition

    Hope this helps


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