Annealing Glass
Annealing glass is similar to annealing different types of metal. Hot glass can be cooled to quickly and can be strained at room temperature. For massive and thick pieces of glass, this can be a problem because the amount of strain depends on how quickly the glass was cooled. The quicker of the cooling the more likely breakage and straining occur.
Breakage can occur at small temperature changes, which allows glass to break off in large jagged shards. To anneal glass it needs to be heated to its annealing temperature. This is normally in the range of 850°F -900°F. These ranges are also called stress relief points. At these temperatures glass becomes viscous. The viscosity of the glass is soft enough to relax the internal strains of the glass. The external strains on the glass are still prominent. The piece heat soaks until the unit can have unformal stress relaxation. Heat soaking is the process of reducing the occurrence of spontaneous breakage. The time of heat soaking varies from glass to glass. Glass can differ in crystalline solids do to not having a distinct melting pints. The difference is due to the chemical bonds that hold the atoms together. The chemical bonds are solid when the temperature is above the specific melting point. The melting point is when the glass becomes viscous. From here, the class can be cooled slowly without problems. After annealing the glass can be cut, drilled, sized and polished for use.
