If you’ve ever done any stained glass, you know it’s very easy to crack glass. It’s not about “how hot it was in the kiln”, but basically thermal shock.
With a 2″ wide piece, you can easily get the glass hot enough to thermal shock. Go slowly, allow the glass time to cool as you work, don’t work in any one area for too long… I’ve also been pondering (saw your question on another board), if there is a way to work on top of a surface that acts as a heat sink but I haven’t come up with any good ideas .
It’s tricky. I used to do stained glass vases and there was one design I worked on that I would crack the same piece several times before getting a good one set in place (solder, crack, solder out, cut new piece, solder, crack, solder out, cut new piece…). . The real pain is soldering out what you’ve already soldered in! (without cracking more glass!!)
Jester’s Baubles Fused Glass Designs