Interesting project! I have not tried their web site, but suggest that you try Schott and/or Corning for the glass.
Our lab has had very good success propagating and controlling glass fracture using a new technique. We achieve VERY clean, straight fractures, and can make those parallel a...
Stresses generated by thermal expansion (usually non-uniform heat absorption patterns) might be causing your problem, as suggested by others.
Another possibility is breakage caused by nickel sulfide inclusions. NiS induced fractures often occur during cold weather when direct solar beam...
