Cooling Rate
The best would be to shoot for 500. You may slightly vent the kiln sooner but be cautious. Remember the inner parts are always hotter than the outer area.
So when they contract during the cooling process, they can put tremendous strain on the surface area, if it has cooled to much. The piece may come out of the oven and look just fine, only to crack later on due to a change in room temperature or altitude (air pressure). The Mt. Palomar telescope lens was annealed for 18 months. That was the second lens, the first was lost due to cooling to rapidly. Technically the glass should be held at the annealing point 10 mins per millimeter thickness, then brought down slowly. Boro can endure more torture than soft glass and quartz glasses would hardly notice it at all. With a devise called a polariscope you can see the stress in the glass.
I hope I haven't ruined somebody's wedding here. But, oh well, next time start sooner.
Have fun , Wayne
P.S. 1 inch equals 25.4 millimeters if they are solid spheres if not go by the wall thickness.
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