Our laboratory testing uses PPG Carlisle, Pa. 3mm and 5mm float glass with the following firing schedule:

From room temperature to 800F at 300 degrees per hour, hold for 10 minutes
From 800F to1120F degrees at 300 degrees per hour, hold for 10 minutes
From 1120F to1250F degrees at 200 degrees per hour, hold for 10 minutes
From 1250F to 1560F fairly quickly, hold for 10 minutes
Crash from1560F to1020F and hold for 45 minutes
From 1020F to 800F at 60 degrees per hour hold for 30 minutes
From 800F to 300F at 100 degrees per hour hold for 5 minutes

Natural cooling to room temperature
Please adjust hold times for the size of your project. Remember this is only a guide.