Should chemicals or sanding be used to remove marble discoloration caused by grout?
Q. We grouted our beautifully installed marble backsplash with Mapei FA+ (color: rain) without sealing it first. It is now grey instead of white. Is there anything I can do to restore the tile to its natural color? I wonder how much the grout color penetrated the tile and if it is possible to sand off the discolored top layer.. or are there any chemical options? We used honed marble and didn't try to clean the grout with anything (except for wiping off the excess grout with a wet sponge).
A. This problem may require the services of a professional stone restoration contractor. First, try mixing some odorless ammonia and water with a 50/50 mix ratio. Wet the tile and apply the solution with a soft scrub brush. Agitate it and then rinse with clean water. If this does not work, it will need to be cleaned with acetone or a mild acid, however, we do not recommend trying this yourself. Acetone can cause health problems. Acid may give you the desired results, but since marble is an acid-sensitive stone, chances are the acid will cause acid etch damage to the finish. A professional stone restoration contractor may be able to remove it without causing etch damage or restore the honed finish if etch damage occurs. If the grout bled into the stone, a professional stone restoration contractor may be able to remove the grout and poultice the stain from the stone, but this would be a labor-intensive effort. You may be better off replacing the installation in this case, but be sure to let a professional stone restoration contractor have an in-person consultation to confirm such drastic measures are necessary. If you do not have a PRO, contact us.