Kersten’s Retro Renovation blue bathroom turned out beautifully, but she also was honest in sharing some of the problems she ran into. One of them was how the gray grout started to whiten in some spots. When I published her story, I promised to look into the issue, and I think I found the answer. The problem is a relatively common concern in tiling and grouting: “Efflorescence” and “Latex Leaching”. The darker your grout, the more you need to be aware of these issues.
I’m not going to try to explain the phenomenon completely here. Instead, I found two online fact sheets that seem to lay it all out. Reading through them, I speculate that Kersten experienced latex leaching. Latex leaching can occur when too much water (or water with chemicals in it) interacts with colored or grey grout mix, causing polymers in the grout to rise to the surface and whiten. A similar phenomenon is efflorescence, in which minerals in the subfloor (often concrete) below the tile rise through the grout and leave a white residue on the surface.
- Tile USA Efflorescence FAQ — This FAQ makes a clearer distinction between efflorescence (which seems to come from the substrate) and latex leaching (which is an interaction between the grout and water.)
- Mapei Fact sheet [link now gone, it seems] — Lots of good tips here on mixing and applying grout to avoid latex leaching.
Solutions? (1) The Tile USA fact sheet suggests some acids might fix latex leaching; sounds iffy to me, and what would happen to your tile? (2) Use a professional so when it goes wrong you can make him or her do it over. (3) Shop til you find a time capsule, so you don’t have to renovate anything. (4) Another possibility: Use a sand-based grout — presuming there are no polymers — ???? — I don’t know. That’s another story. (5) Lay down a rug, and move on. <– A wise solution.