When exposed to ultraviolet energy and then heated, photosensitive glass changes from clear to opal. When the UV exposure is made through a mask, the pattern of the mask is reproduced in the glass. The image developed is permanent and will not fade, as would a similar image in a photochromic glass. The exposed, opalized photosensitive glass is much more soluble in hydrofluidic acid than the unexposed glass. Immersion in this acid produces shapes, depressions, or holes by etching away of those exposed and developed areas.
Photochromatic glasses are full-color photosensitive glasses.
Developed in 1978 by Corning Glass Works laboratories, their characteristics imply applications such as information storage, decorative objects, windows, or other transparencies, and containers. Photochromic glasses have true color permanence.