Devitrification is the crystallization process of glass. It is manifested by the formation of crystals and a loss of transparency.
This term comes from the Latin word vitreus which means transparent.
As glass is a body out of equilibrium, in principle when the silica (or fluorine) network is heated and then rapidly cooled, the crystalline structure is unable to reform and forms glass, an amorphous structure. Nevertheless, if the glass manufacturing process is incomplete or poorly controlled, over time the glass may partially crystallize and become opaque.
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