Glass, Photochromic

Name:
Glass, Photochromic
Detailed information:
A glass that changes color on exposure to light and returns to original color when the light has been removed. One type is a silicate glass containing dispersed crystals of colloidal silver halide that is precipitated within the melt during cooling. Alkali borosilicates are the most suitable types of glasses for this purpose.

Use:

Variable-tint prescription lenses that darken in sunlight and return to original clearness indoors (85% light transmission when clear, 45% in sunlight).