Dear Rebecca:
“The builder acid washed it to try to clean it up”
That was the worst “solution” to the problem one could think of of! Only a person who does not know the first thing about stone and, on top of that, does not ask for any advice before doing things, could come up with such a “brilliant” idea!
Considering the fact that you have a mural painted over, there's no solution. The restoration of the stone surface would require a process that would take the painting off.
Of course, before the acid wash it would have been possible to fix the grout film problem pretty easily. It's too late now.
Well, at least now you know whom to charge for the replacement of the tiles… :-)
Ciao and good luck,
Article ID: 13
Created On: Sun, May 6, 2007 at 8:13 AM
Last Updated On: Thu, Jul 16, 2009 at 12:00 AM
Authored by: Maurizio Bertoli [mail@mbstone.com]
Online URL: https://marblecleaning.org/knowledgebase/article.php?id=13