Visitors watch the blowing and assume that’s where pieces are lost — a bad gather, a drop, a crack at the punty. Almost never. The furnace work either goes or it doesn’t, and you know within seconds.
The annealer is different. A piece cools overnight on a programmed curve, and if the wall thickness is uneven enough, the stress finds it at 4 a.m. with nobody watching. You learn to read the morning silence before the door opens.