Anneal
Slow cooling from 900°F to room temperature, so the glass doesn't crack.
The slow part
Hot glass wants to crack. The annealer cools it from 900°F to room temperature over twelve hours, easing the stress out of the structure.
The numbers
annealer 900°F start ramp -50°F per hour, held time 12–16 hours result glass that won't shatter later
Why it matters
Skip the anneal and the piece looks fine until it isn't — a crack, days later, out of nowhere. Patience is the last tool.