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 1100F degrees at 600 degrees per hour, hold for 10 minutes
From 1100F to (1225 to 1300F) ****degrees at 600 degrees per hour, hold for 5 minutes
From (1225 to 1300F) to1020F degrees fairly quickly "9999" 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.
**** Requires eye contact. Remember this is only a guide.