We had some marble tiles layed the other day- without sealing them first- they were polished tiles. Grout was applied and left on for at least a day or so and we were told to get the grout off by a damp mop which we did. It has left marks on the marble tiles and made them look very dull. Would these marks be the result of water or the grout ? They aren’t dark obvious marks – just looks like translucent marks across the surface of the tile in sunlight. Just a case of polishing them ? Anon
ASAA
Australian Stone Advisory Association Ltd
Without knowing the stone type it is dificult to provide an exact answer. It is likely that the water soluble portion of the grout has travelled into the surface of the stone or the fine residue has been trapped within the fine pits on the surface of the stone. Both causes are unsual for well polished good quality marble as this stone is usually very fine grained and has a very low porosity. A stone such as an unfilled limestone is more likely to have small pits that will trap residue and these type also generally have a higher porosity. In either case it is worth trying to remove the residue with a CLEAN damp cloth and CLEAN water, ensure you keep both clean by continually changing water and cloths. The aim is to remobilise (or dissolve) the residue near the surface without adding more water to the stone than is needed. It will be useful to let the surface dry in between cleanings and then wipe with a barely damp cloth to pick up any residue deposited on the surface as the water has evaporated. Jim Mann (member)
Grout is alkaline in nature and can be corrosive in nature just like acid . It is possible that the grout has etched the polished surface. I would suggest getting a qualified opinion onsite from a stone surfacing company. Anonymous