Glass Annealing Explained
Annealing relieves internal stresses in glass by holding at the annealing point (where glass is soft enough for stress to relax) then cooling slowly through the strain point. Below the strain point, glass is rigid and stress can no longer be relieved.
Thickness and Time
Annealing time scales approximately with the square of thickness. A piece twice as thick needs roughly four times the annealing soak and proportionally slower cooling rates.
- 1/4" (6mm): 30-minute soak, ~2 hours total
- 1/2" (12mm): 1-hour soak, ~4 hours total
- 1" (25mm): 4-hour soak, ~12 hours total
- 2" (50mm): 16-hour soak, ~36 hours total