The term literally means "un-glass" and means just that Under certain adverse conditions the elements at the surface of glass can break down and leave a white powdery-looking deposit Sometimes devitrification can be eliminated by reheating, but often it cannot and it must be removed by acid-polishing
(1) The process whereby glass becomes partly crystallized as it cools (usually too slowly) from the molten state; (2) the crystals formed by this process Devtrification may also occur on the surface as a result of the unstable composition of the glass, unsuccessful annealing or accidental firing It is not caused by reaction between the glass and its environment, which is known as weathering
Specifically, the conversion of molten glassy matter into a stony mass by slow cooling, the result being the formation of crystallites, microbites, etc
The crystallization of a ceramic melt during cooling Devitrification is desirable in achieving certain visual effects (e g matteness) and undesirable when a transparent or glossy transparent glaze is desired