Annealing Thick Slabs | Kilncasting

Glass for Art and Architecture

Annealing Thick Slabs


Annealing Thick Slabs (Fahrenheit)



Annealing Thick Slabs (Celsius)



When a piece of hot kiln-glass is returned to room temperature, it cannot be allowed to cool too quickly. If cooled too quickly, the temperature differential throughout the glass can become too great, which may cause thermal shock or introduce stress into the glass.

This is why we cool kiln-glass slowly as it passes through the “annealing range”. If we cool kiln-glass at a slow enough rate, we can ensure the temperature differential throughout the glass is minimal.

This annealing chart has been formulated for use with Bullseye clear glass. It is based on a flat slab of uniform thickness that is set up in such a fashion that it can cool equally from top and bottom.

Helpful Resources

Video lesson: Why Did It Break?
TechNote 4: Heat and Glass
TechNote 7: Monitoring Kiln Temperatures for Successful Annealing
Recommended Annealing Cycle for Bullseye Glass

Featured Products

Bullseye Billets

Revised December 8, 2020.