I did purchase the liquid masking coating for marble and stone surfaces.  It’s an unusual application I am sure, but we installed a new kitchen backsplash with a green/white marble tile and the grout color is a dark green.  When testing grout on tile samples I had problems with the marble absorbing the grout into surface of the tile and turning the white marble dark and greenish muddy looking.  It was not good.  Reading up on tiling I found that natural stones and marbles will absorb grout unless you seal the surface.  I tried various tile sealers sold for this purpose and none of them worked well and the tile always ended up dark and blotchy.  So, in desperation, I started looking outside the box of traditional tiling methods and was looking for something that I could coat the face of the tile with, grout and then remove again.  I came across your liquid masking coatings through an internet search. 

To wrap up a long story, the coating works tremendously well.  It went on easy with a simple paint roller (a small detail roller with a short nap) and does a great job at minimizing the absorption of the grout.  I was very pleased with the results of all of my sample pieces.  I did find that I needed to use multiple, thin coats, about 2-3 coats, for the best results, but the can of coating I purchased goes a long way so I have more than enough.  The coating peels off really easily and actually reduces the effort to wash the grout haze off the tile, as the haze is on the coating, not the tile.  The final backsplash grouting is going to take place sometime over the next two weeks, but I am confident I have found a perfect solution to the problem.  Great product!  Thanks so much. Brenda