[joshmillard]

I got to use the studio's supply, so I haven't had to really sort out glass buying myself. And yeah, I was lucky to benefit from access to a really great collection of glass. But there are some commercial firms (Spectrum does very flat, transparent glass; Delphi does stuff with more character) and you can go haunt estate sales, watch for hobbyists getting out from under their supply, check with art schools, etc.