How to Clean Soap Scum Staining on Limestone and Slate?


Soap Scum Staining on Limestone and Slate - I have a bit of a problem. I have a walk in shower that is made from slate and limestone. Slate on the walls and limestone on the floor. Both of these tiles are rough not smooth and they have been finished with an exterior sealant. Over time soap scum has set in and I have tried everything that I can think of to clean this but I am not getting anywhere. Do you have some suggestions?


ANSWER - The more texture you have on a stone finish the more difficult it will be to clean and the more often you need to clean it.  Sealers help because they act as bond-breakers and will help keep residuals from attaching to the surface and it helps make it easier to clean it, but you need to re-seal regularly.  If you sprinkle water on the dry surface of the stone and the water does not bead up (like water on a car's new wax job), then you need to reapply the sealer.

There are a variety of sealers and strippers that can be applied that should remove soap film if you use a brush to abrade it off, but you have to be careful not to scratch the stone surface.  To find a suitable cleaner go to our website at to Expert Answers to find Resources and click on Cleaners and Sealers for a list of manufacturers with links to their website.

2 thoughts on “How to Clean Soap Scum Staining on Limestone and Slate?

  1. Kathy Mason says:

    Help I just looked at a slate shower and the soap scum is so thick that when I scratch it with my finger nail the slate falls off in my hand. The slate is so white from soap scum. How do I clean this shower?

    • Donato Pompo says:

      If in fact it is soap residue, get a liquid detergent and add to a buck of water and then get a scrub brush and brush the wall down. I would take the hot water from the shower and spray the wall first to loosen up the soap. After scrubbing with the brush and detergent be sure to rinse the shower down.

      It is possible the scum is actually from hard water is calcium residue. If that is the case you need to buy a cleaner that removes calcium build up on slate.

      Once the tile is clean and dry you should treat it with a penetrating sealer such as Miracle 511 Impregnator. Slate is very dense so it won’t absorb much. Follow the product manufacturer’s directions. Use lint free cloths to apply sealer and dry lint free cloths to buff it down right away after applying the sealer so the surface does not remain wet or it can get sticky.

      After shower you should wipe the shower down with a towl.

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