Bostik TruColor premixed urethane grout: opinions?
At the risk of repeating myself...
Judging from your description of the electricians' work, they did not adequately shield the newly grouted floor when cutting the drywall, and the fine gypsum powder has been tracked into the (microscopically) irregular surface of the grout.
Their claim that they "cleaned up" or "put tarps down" -- whatever they may have told you -- can be shown to be true or false by testing for gypsum dust in the grout.
You can let the electricians know that you believe they did not protect the floor before cutting the drywall, and your intention is to have the grout surface lab-tested for embedded gypsum dust. But to spare you (and possibly themselves) the expense of the test itself, and the cost of having a third-party clean the floor, they could come over and gently scrub your floor, by hand, with a soft-bristled scrub brush, no mechanical devices, and lots of warm water (no chemicals), which they must wet-vacuum up so the dust particles suspended in the water don't just settle back down into the nooks and crannies of the grout surface. It might take three or four or even six such gentle scrubbings and wet-vacuumings to remove the dust.
That approach gives the electricians an honorable, non-litigious way to try to fix, with the sweat of their brows, a problem they have created. If they balk or stonewall you or finger-point at the grout manufacturer, then you can proceed with the lab-test and take appropriate legal action depending on the results of the test.
This is not a grout product-defect, judging from everything you have said.
Last edited by diy888; 02-08-2013 at 01:58 PM.