Carrarra Marble Tub/Shower Surround

Q.I have honed carrerra marble walls as shower surround over tub. The marble when wet turns dark grey. I do not know if the installer used grey or white thin set. Do I need to use impregnator? Is this just natural and I should not seal further? The installer did seal initially.

A.Hello Penny. Your marble is absorbing water and gets darker until the water dries out.

Is it happening on the floor and the lower walls. Have the installer come back and seal the stone until it isnt absorbing anymore water. It will probably take several coats.

Also it would help to check the joints where the floor meets the wall and make sure they are caulked very well. This should solve the problem.

Stu Rosen