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

From room temperature to 800F at 500 degrees per hour, hold for 10 minutes
From 800F to 1250F degrees at 200 degrees per hour, hold for 10 minutes
From 1250F to1375F degrees at 200 degrees per hour, hold for 10 minutes
From 1375F to1090F degrees fairly quickly "9999" hold for 30 minutes
From 1090F to 970F at 100 degrees per hour, hold for 30 minutes
From 970F to 830F at 100 degrees per hour, hold for 20 minutes
From 830F to 720F at 100 degrees per hour hold for 1 minute
Natural cooling to room temperature
Please adjust hold times for the size of your project. Remember this is only a guide.