My customer’s shower floor is made of a flamed granite. A hard white deposit is starting to form between the grout lines. What is this, and what is the best way to clean it?

The hard white deposit is a build-up of salts. These salts—known in the tile industry as “lime putty”—are coming up from the setting bed, and can be very difficult to remove. To remove lime putty, scrape away as much of it as possible using a putty knife or razor blade. Next, use a solution of muriatic (hydrochloric ) acid in a dilution of 1:1. This should dissolve the lime putty . Be very careful, and make sure there is adequate ventilation. Hydrochloric acid emits caustic fumes which are very dangerous. Wear an approved acid fume respirator and use an exhaust fan. Also, protect any metal fixtures, since the acid fumes will tarnish metal surfaces. This is a job for which you should definitely consider hiring a professional. When all the lime putty has been removed, and the tile is completely dry, apply a good-quality silicon sealer to help prevent reoccurrence of the putty.