Pulled out a portrait panel I finished last spring, one I shipped to a client in Athens, and she sent me a close-up photo today asking if this was supposed to happen. The deep blue smalti has this white bloom creeped into the edges, right where the grout sits. Efflorescence, I know the word, I've seen it on outdoor work, but this thing has been in a dry apartment for six months.

She's not angry, she's asking. But I don't have a good answer and it's eating at me. I used a standard grey grout, cured it properly, sealed it. The theory I've got now is I left the tiles a hair too close together on that section and the grout couldn't seat right, so moisture sat in the joint instead of drying out.

I've done this twenty years. Still can't tell whether it's my mix, my joint width, or the stone itself weeping from somewhere I can't see. Anyone else seen smalti bloom like this indoors, or did I mess up the recipe and I should just own it and offer to re-grout on my dime?