Cleaning Slimy Slate in a Shower

Cleaning Black Mold from Slate in Shower

Mold on Slate

Gary J. from Phoenix called to discuss a problem he has with Mold growing on his Slate in a shower.

“We installed slate in our shower about 3 years ago and it has slowly been harder and harder to clean the tiles  and prevent mold from growing in the joints, and the surface of the slate is quite slimy”.


This is a common problem in high humidity areas and where the stone or slate in this case has not been sealed in quite a while.

First Step is to kill the mold. One of the best products to accomplish this is Professional

Clean moss, mold, and mildew from natural stone

HMK R60 Mold & Mildew Remover for Natural Stone

Grade HMK R60 Mold & Mildew Remover.

        • Spray on the surface and allow to dwell for 10 minutes.
        • Scrub area with Medium stiffness Scrub Brush.
        • Spray area again and allow to dwell for 10 more minutes.
        • Scrub area once again and rinse completely. Repeat if necessary.

R60 will Kill the Mold, and also Prevent it from Returning!

Next Step is to  Deep Clean shower using a heavy duty cleaner made specifically for Natural Stone. We recommend using HMK R55 Intensive Cleaner for deep Cleaning. R55 will clean all residual mold, mildew, soap scum and remove residual elements from the pores of the stone, preparing the stone to be sealed.

      • Mix a solution of R55, 1 part to 5 parts water.
      • Use a Scrubbing Sponge, Scrub Brush or Sponge to apply to stone walls and floor.


        Scrubbing Sponge

      • For large showers, we recommend using our Professional Grade Wash Stick to make the job much easier and for regular cleaning.

Stone Wash Stick

      • Rinse area completely and allow to dry for 24 hours before applying Impregnators. Topical Sealers are NOT recommended for wet areas.

For Natural Cleft Slate I suggest using either a clear – invisible Impregnator like HMK S34 Silicone Impregnator, or if you like the look of the Slate or Stone when it is wet, you may prefer using a Color Enhancing Impregnator like HMK S42 Exterior Color Enhancer.

By Killing the Mold, Deep Cleaning the Stone, and Impregnating the Slate, you will make regular cleaning much easier and reduce the occurrence of Mold and Mildew.
After regular cleaning and maintenance, spray area with R60 as additional protection.

About Torin Dixon

StoneCareOnline Expert Blog is managed by Torin Dixon who is an expert in natural stone importing, distribution, fabrication, installation and maintenance of all natural stone surfaces regardless of finish or texture. We are here to assist you in your StoneCare needs.
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