Re: Emitting a loud "crack!...
"Over a few weeks each of the initial bunch made out of soda glass developed cracks at at least one joint. They had to be remade in Pyrex."
Soda glass needs careful annealing; borosilicate has a much lower coefficient of thermal expansion and doesn't.
I've watched the (amazing) machine that makes laboratory glass tubing. It's enormously long, so as the molten glass is extruded and drawn to correct diameter it cools slowly enough not to lock in stress. But having said that, if you have a lot of bends that need careful cooling, it will probably save a lot of time if you use borosilicate glass in the first place.
Biting the hand that feeds IT
