Thick Glass Firing

by Tony Roberts

My schedule for 50mm (2 inch) Pilkington’s Opticlear in a top-heated flatbed kiln is:

0 to 600C - 6C per hour rise - takes 6 days (if you start with a solid slab) (I start with smaller pieces, so can raise the temp much faster)

600C/hr to your soak temp - as fast as you like (I go to 840C and hold 4hours)

Soak temp to 565C - drop as fast as you can, then hold for 14hours

Anneal: drop at 0.75C per hour to 365C - this takes 11 days

Then drop at 1.5C per hour to 300C - another 2 days

Then drop to 60C at 4C per hour - 2 days and a half



A total of 16 and a half days