Sealing grout and caulking new shower...

[John Pride]

Hi, everyone. I'm an old retired-ish contractor who's done a lot of bathroom renovations. I'm home now, doing three baths and some other stuff at my home while my body allows me to work at a slooower pace.

I'm all "tiled out" on the first bath. I've grouted everything, using Mapei Ultracolor Plus FA. I used gray on the floor and white on the walls.

FIRST QUESTION: The gray on the floor (main bath floor, not shower floor – shower floor was mixed less dry, went well) set up FAST, but was pliable enough to finish the area. Once it cured (it’s been a month or so), it shows some inconsistency in appearance, lighter like efflorescence in some places. What can I do to “even out” that appearance? I haven’t sealed that grout yet.

Now, here’s my primary concern: I left the vertical corners and the joint along the floor open for caulking. I’ve sealed all shower grout walls and floor (but I held back where the grout enters a caulk joint – see below) with Miracle Tile, Stone & Grout Sealer, their water-based low VOC formula.

SECOND QUESTION: Is this a suitable sealer for a shower? If not, can I go over it with 511 or something better?

I want to seal the grout (and maybe even the cut edges that caulk will be against) be absolutely impervious, because I hope that’ll reduce caulk separation and frequency of re-caulking. If the water-based formula isn’t going to do that, I’d rather change now than add another application of something that won’t do the job.

THIRD QUESTION: If I seal the grout that’s intersecting the caulk joints, will silicone caulk stick to it? Does this answer change if I use 511 vs. water-based sealer?

I can't get a straight answer from either Mapei or two caulking manufacturers. They suggest that I do a test of my own. Hmmm. 3 test labs, everyday applications, and friggin' crickets from the experts.

That’s about it, at least until I see any responses. I appreciate you expert professionals taking time to advise us amateurs!