I have a bathroom on my deck (essentially an "outhouse"). I redid the floor with external-rated porcelin tile, set in Keraset/Keraply (also outdoor rated: ANSI 118.4). I used the same grout I had used for a glass backsplash. The only warning was that the grout not be exposed to freezing temperatures for at least 21 days. Temperatures were mild, and there was no contact with moisture other than humidity in the air.
On the glass backsplash, the grout went on dark gray and dried light gray. On this ceramic floor, it went on dark gray and dried to an inconsistent coloring: some to the expected light gray and some areas to a semi-dark gray. It has been a week; so I don't expect the darker gray is because the grout hasn't dried thoroughly. I'm left with the problem: how to turn the darker gray to a lighter gray or even a tan? Would an opaque concrete stain cover the darker color? Is there a better way? Are there, perhaps, incantations that might work?
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