[Tink]

Most bottle glass is around 90 COE. I say "around" because it varies so much, even between beer bottles from the same six-pack. Bullseye used to use recycled glass as a base for their products, which they stopped doing almost twenty years ago. That's kinda how their line ended up being in the 90-ish COE range instead of higher, like the Italian glasses.

Anyway, to answer your question, Mary: The only way you can find out the COE of a piece of glass is to check it with a dilatometer within the appropriate temperature range.

But COE alone isn't enough to determine compatibility.

While it wouldn't be prudent to mix recycled glass with other glasses, you have a lot of options for fancying it up: Pixie Dust, as was mentioned... metal leaf and foil... Not to mention the shape of the piece itself. Some of the most beautiful works I've ever seen have been made from just one color.