Should unsanded grout become darker when wet?

Question

Anyone who recognizes me at this point will know I've been working on remodeling our bathroom (Should we use a tub surround and Curing time for grout with GroutBoost).

We finally finished everything up, let the grout dry and cure, and caulked around the tub. I used the shower with no plastic over the tile for the first time this morning, which, of course, gave me plenty of time to examine my workmanship.

I found a few little bits of grout on the tile faces that I was able to scrape off with my fingernail. I also noticed that the grout turns much darker when it gets wet, and when I rubbed one of the grout seams with my finger, I was able to get a little cloudy water on my finger. The grout seems hard enough otherwise and dried fairly quickly (returning to it's normal color).

We didn't seal the grout as we used Grout Boost Advanced Pro, and per their FAQ:

Does grout mixed with Grout Boost ever need to be sealed?

No. Since Grout Boost is mixed with the grout, the stain resistance is throughout the grout and can not erode like a sealer.

This is what it ended up looking like:

Click for large version.

Is the color change normal for unsanded grout? I am unsure as it didn't happen with the tile we took out. Also, is it okay I was able to scrape some leftover grout off the tile? I want to be sure my grout dried and cured properly.

Answer 1

Very nice looking job Jared, congratulations! It is very normal for unsealed grout to change to a darker color when wet. This will happen even with fully cured grout. Feel free to buff any excess grout or haze off your tiles, it won't hurt anything and that also is normal for newly installed tile. If the darker color when wet bothers you, then go ahead and put a couple of coats of grout sealer on after about two weeks from the original grout date. Even though the manufacture claims stain resistance, it does not claim to stop the temporary color shift when wet. Sealing the surface of the grout will stop the wetting of the grout and end the color changes. You may find you need to reapply some sealer every year or so in a shower surround. Apply the sealer with a small foam brush just to the grout, Buff excess off the tiles 15 to 20 mins later. Looks Great!!! Good Luck.

Answer 2

The colour change is normal. How much you notice it depends on the colour of the grout. For white grout I don't remember ever noticing it, but for darker ones it is obvious when the grout is wet.

Grout does take a long time to go fully "off". It's usable after 24 hours or so (depending on the grout), but will take more time to fully harden.