Image Credit: Mo-Sci Corporation
The glass annealing process relieves internal stresses, which could otherwise leave it vulnerable to fracturing or shattering in response to minor mechanical or thermal shock. This makes annealing a crucial step in the manufacture of robust, stable, and heat-resistant glass.
Why Anneal?
Physically speaking, glass is a rather unusual material. Most solid materials are significantly ‘ordered’ with their constituent molecules or atoms in a regular arrangement, repeating patterns called crystal lattices. But the molecules in glass follow a different set of rules: they are, by definition, disorderly.
In fact, the way solid glass molecules are arranged resembles that of a liquid, except that they are fixed in place and don’t move around. It is said that glass is an amorphous solid.