Chameleon in the sun: photochromic glass

The properties characterized as photochromic¿the ability to react reversibly to light¿are found in various substances, both organic and inorganic. The two classes of materials are compared and the mechanism of the process is examined in each case. Of primary interest here are the inorganics, particularly the silver halide reversible photochromic glasses. Properties and ranges of properties of these are reviewed and some possible applications described.