I had tiles and grout laid approximately two months ago and since then the grout color has been changing, or more accurately, the grout is getting white blotches, more blotches as time goes on. My customer, as you would imagine is quite miffed and my tilesetter has never seen something like this – neither have I. The tiles were set on a scratch coat over a plywood floor. Has anyone experienced this? What do you think can be done?
Thanks,
David
Replies
http://aldonchem.com/section-answerbook.htm
Sounds like efflorescence.
I believe too wet a mix can cause this.
The usual cure for efflourescence is to wash it out with lots of water.
sponge on,
sponge off,
sponge on,
sponge off
etc.