areas of dark grout lines in new shower
Our shower has just been redone (because of mold/leaking/improper tiling job). It looks beautiful, except that the medium gray grout lines are staying dark. Immediately after showering, most of the grout appears wet. Several hours later and even 4 days later, the are multiple areas where the grout remains dark. They are in different areas - along the edges, some by the drain and others near neither the edge or the drain.
I discussed this with my contractor and tiler who first questioned if we were using the fan. Yes, we are using the fan and leaving it on for hours and days and leaving the shower door open. Then, the tiler came back out and said that the grout is staying wet because of the mud base becoming saturated and remaining wet. As the mud becomes more saturated, the darker areas may even begin to change. He said that when demo-ing some showers that haven't been used in weeks to months that the mud base can still be wet. (yes, but were they supposed to be?)
My main concern is mold becoming a problem. If the tiler's explanation is basically that the grout is never drying out because the mud base remain wet, then won't there be mold problems?
I have been reading the forums and know to ask about adequate preslope (not just slope) and clogged weepholes and what mortar mix was used. I just wanted to make sure that this wasn't an adequate explanation before I proceeded.