I've wondered that myself! Especially on BB's that are left outside in the elements. Kathy

I aint no expert, but I think you'd need to rough up the surface to give it "tooth" before you paint. Then I would use a primer paint.

I've done plain substrates and painted ones . . .doesn't seem to be a difference and haven't had any problems. That said, I understand the concept of "I'm really gluing to paint" rather than gluing to the substrate.

Interesting. I'm looking at mosaicing the insets of
the doors in our TV armoire and was wondering about
the technique and longevity. Thanks. Maybe I'll use a solid glass instead since I'm a bit of a worry wart.
Linlee

I have several bbs in my yard that I made just this year and they are all painted underneath the glass globs. I sanded them down with an orbital sander and 60 grit sandpaper. Then I go over it by hand with 120 or 150 sandpaper. I paint with outdoor paint or use spray paint. I worried about the glue holding in these temps. but that wasn't a problem either. I used Lexel silicone to glue the glass globs on (these were made before discovering this forum and GEII)and I did not use grout. So far no peeling problems.