Casting & Annealing Fundamentals

A brief explanation of the principles for Casting and Annealing Glass, as well as a description of important terms.
1. Annealing Glass: controlled cooling from working temperature to room in a manner that removes
strain and stress from the glass body.
2. Annealing Point: the temperature ABOVE which glass begins to move.
3. Anneal Soak: holding the glass at a point between the Annealing Pt and Strain Pt. for long enough
to equalize the temperature throughout the material.
4. Strain Point: the temperature BELOW which we cannot permanently add or remove stress.
5. Annealing Range: the temperature range (between the Annealing Pt and Strain Pt) where stress
can be removed from glass.
6. Quartz Inversion: the sudden change in size/shape of silica particles at roughly 1160ºF.
7. Devitrification Range: the temperature range where glass begins to turn back into it's crystalline
form. This often appears as a wrinkled or frosty surface and can be so bad the glass begins to
self-destruct.
8. Process Temperature: the working temperature of the glass—whether blowing, casting, slumping,
fusing, etc.
9. Anti-Shrink Zone: the temperature range where slow cooling can prevent "suckers" in the surface
of the casting.