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Tile and Stone Maintenance

Cleaning Slate – Expert Advice on Cleaning Slate and Slate Floors – Part 2 »

Some detailed instructions with regard to cleaning slate floors:

If the slate floor is adversely covered in cement or grout residue:

1. Use water to pre-wet the floor.

2. Apply some phosphoric acid-type cleaner solution to the floor – mixed with 1 part cleaner to 5 parts water to begin. (You can use a stronger mix if required). **PLEASE NOTE: Always conduct a small test on a relatively inconspicuous section of the floor first, before you begin.

3. Leave the cleaner to dwell on the floor for a few minutes

4. Agitate the floor and cleaning solution with a scrubbing brush (nylon bristle and not metal).

5. Soak up the cleaning solution remaining on the floor. Rinse well with fresh water, agitating again so you can get rid of any residual acid cleaner.

6. Make an assessment of the floor at this stage. You may need to apply an additional treatment of the cleaner.

If your slate floor only requires routine cleaning we would recommend a neutral cleaner like Ezy Clean by All for Stone – this is a mild cleaner and is safe and suitable for cleaning slate on a regular basis.

For more intensive slate cleaning, where the dirt is not mineral- based, we would recommend the use of a heavy-duty alkaline cleaner like Xtreme Clean. This a powerful cleaner and degreasing solution. When applied to the floor, leave to dwell for between 5 and 15 minutes, depending on how bad the contamination. Then agitate by scrubbing with a nylon or natural bristle scrubbing brush. Clean up remaining the dirty solution and rinse well with clean water.

The critical elements here are the dwell time and the rinsing. Alkaline-cleaning solutions need time to work. Once you have “extracted” the dirt from the floor it will be suspended in the solution so you absolutely must remove it – on no account leave it to dry naturally.

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


  1. Ian

    I just bought a home in the mtns of CO and the showers have slate in them. There seems to be an iron like substance in a couple of them on the floor. First, what exactly is it, second, how is it caused, third, how do I get rid of it, and fourth, can I prevent it. Hoping you can help.


  2. HI Diane,

    OK, when you say Iron-like, do you mean rusty looking?

    Many slates have, as a naturally occurring mineral, some form of iron in their makeup. It is completely random and perfectly natural, not a ‘fault’.

    If however there is some surface rust, that is, some rusty deposit that has landed on the slate, usually from some rusty item above it, either in the current situation (rusty faucet, fitting etc) or something that the slate was in close proximity to during storage (strapping band with steel fasteners for example) then this is not an inherent part of the stone, but rather a deposit that has been left on the surface. This can often be removed with a mild, phosphoric acid based cleaner.

    Sometimes, where there is naturally a occurring iron-bearing mineral, it only starts to oxidise (rust when the slate is split, and installed, (thus exposing the iron to moisture and air) – so it rusts at the surface, sometimes a phosphoric acid based cleaner can help remove or at least reduce, this also.

    There is no real way of stopping it reoccur if it is natural iron, sealing it may help (reduce the ongoing contact with moisture), but it may settle down over time in any case.

    Hope this helps


  3. My son has a slate floor in his kitchen and lounge. In the kitchen there was a larg cupboard now removed for the new fitments This had beeen there since building in 1960. It is dark gray but a much lighter “dusty” colour;

    How o I clean it up? Hyrogen hydroxide has not made any difference

  4. Hi Valerie,

    Hydrogen Hydroxide? – do you mean water?

    Anyway, for old slate like this my first test would be with an alkaline deep cleaner, like Xtreme Clean. maybe with the addition of a micro abrasive cleaner like Microscrub.

    It all depends on what you are trying to remove, the above works well on general ingrained grime but if the slate had been previously treated with some kind of sealer, oil or coating then you may need something stronger

    Kind regards


  5. I have a friend who was doing a spray paint project on her slate patio and, even though she put some cardboard and plastic down, she has overspray on whatever wasn’t covered. What can she do to remove it?

  6. Hi really she needs a paint stripper.

    You can saturate the slate esp the area surrounding the stain with warm water, wipe the water away from the paint area – this can just sometimes help to prevent the solvent based paint stripper from pushing the thinned paint deeper into the stone.

    Apply a stripper, leave for a few seconds, rub, and immediately wipe up any dissolved paint with absorbent paper towels etc. repeat if needed, each time removing more of the paint. Do not let the solvent / paint dry, always remove what you have dissolved before it dries.

    Hope this Helps


  7. Hi there we have slate window ledges but they have been painted’ we would like to restore them to their former, glory how would you recommend we do this?

  8. Hi, you are going to need a paint stripper I think, a chemical one. You could try a heat gun first, if you can get the paint to peel off with one of those you may get a way with a nice clean stone. If not look for a paint stripper, to suit whatever type of paint it is, then conduct a small test on one corner. As soon as the paint softens try t remove with a plastic scraper or similar so as not to scratch or gouge the stone. Then wipe away excess stripper and rinse with a nylon scourer/sponge and fresh water. Let it dry and evaluate the degree of success – it may work first time or may require a second go.

    Hope that helps

  9. Catriona Lynch

    April 30, 2016 at 7:36 pm

    I used a softish kitchen scorer on a section on our slate fireplace. The area has gone all dark, Matt and generally dirty looking . Is there any way to repair the damage? Thank you in anticipation

  10. Hi,

    I am not entirely sure what has happened here, it could be that you have inadvertently removed some coating / oil/ wax or other finish, or you have partially polished the surface – to a very small degree, or a bit of both. Any chance you can send me a picture?



  11. Hi, I have split slate tiles on the wall. We made a mistake and put on ‘colour intensifier’ and it is turned black instead of the grey tones. We want to take it off and get back to the grey. Do you have any ideas how we can do this please?

  12. Hi, All I can suggest is a very strong alkaline cleaner or perhaps a solvent stripper – but the first thing I would do is to call the manufacturer of the colour intensifier to ask what their recommendation is.

    It might be that you cannot remove 100% of it, but you may be able to reduce the intensity to an acceptable level>

    Hope this helps


  13. Hi, we have a beautiful Lakelans cottage which is 120 years old and has original slate flagstones in kitchen and lounge. We recently needed our kitchen rep mastered prior to have the kitchen updated and the plaster dust is proving hard to get rid of. I have used washing up liquid and a nylon scrubbing twice. Then used bleach and elbow grease. It has improved but not gone. The floors are not sealed. Would an acid- based cleaner be best? Hope you can help.

  14. Hi, a very quick answer, yes I think that a very diluted cleaner based on Phosphoric Acid will help, as the plaster is a mineral product and needs something to actually dissolve it. Look for something like my Grout Haze Plus on amazon or other products that are similar such as HG Extra

    you will need to a) dilute at least 1:5 with water, b) rinse well with water afterwards and c) do a test area first

    Hope this helps


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