10 minutes held at the annealing point per millimeter thickness. Mt. Palomar telescope lens took 10 months to bring down to room temperature. They blew the first lens by cooling to fast.
This is especially important in thicker pieces. 25.4 mm = 1 inch x 10 = 254 minutes held at the annealing point. When the temperature reaches down to 500 degrees F you can vent the oven a bit
and cool faster.
|