We recently had a Thasos Marble floor installed in a kitchen remodel. The flooring contractor used black grout. Due to the pourus surface there are now black specs in the pours and the entire tile has taken on a haze. Is there anything that can clean this surface and what is the proper installation for this type of situation with a pourous surface and black grout
Dear Michael:
The proper installation technique for this type of situation is not to use black grout with white marble. As simple as that.
Anything different, would spell, T-R-O-U-B-L-E.
You're experiencing it right now and, quite frankly I don't have a sure answer to your problem, assuming that there is an answer.
White Thassos is not very porous to begin with, and the "haze" cold be extensive etchings due, maybe, to the use of a grout film remover (most of which are acidic in nature) that your contractor may have used to desperately try to clean all the black stuff from the surface of the stone.
Only a proficient stone restoration contractor may be able to help you; but had you called me in my contracting days, my answer would have been that I'd have to possibly run extesive testing in the attempt to find a solution, with no guarantee of success, and that I would charge you through the nose for all the testing.
Bottom line: poor choice of flooring material (polished pure white marble in a kitchen???...) and then the black grout thing... Oh my my!...
Sorry, but, tsk, tsk, tsk... :-(
Ciao and good luck,
Maurzio Bertoli