Photochromic glass is usually referred to as photochromic glass.
This glass changes color by:
Silver halide, such as iodide, is an unstable compound that breaks down into iodine and silver when exposed to light. When the light is dark, iodine and silver will recombine into silver iodide, presenting a colorless and transparent state.
Use this one characteristic, in the place with stronger illumination is used outside window, vitreous hair is black in the day, can block effectively the light intensity that enters interior, form had an shade curtain together; At night or cloudy, the glass appears colorless and returns to normal lighting.
Because of the high cost, the glass is used sparingly in buildings, mostly in the form of discolored sunglasses.