Nice result Kal by salvaging this... Sucks that it broke though... I just tried something to speed drying plates up at home. I have a small coleman catalytic heater that I place under a f our legged metal flower pot stand and use a large 1' square tile on top of that.... The heat dries plates in a few minutes with even and flame free heat.. It can also be used for varnishing tihs way too.
If it's glass it's probably the difference in heat between cold and hot parts of the plate that creates enough tension to crack it.
I had a gallon amber jar full of seasoned print developer do this to me in the darkroom recently, as I was trying to warm it up to working temperature, just using warm water. It doesn't take much.
I think Andrew's idea of even heat distribution is perfect.