Photochromic Glass

Also found in: Dictionary, Thesaurus, Medical.

photochromic glass

[¦fōd·ō¦krō·mik ′glas]
A glass that darkens when exposed to light but regains its original transparency a few minutes after light is removed; the rate of clearing increases with temperature.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Photochromic Glass


an inorganic glass capable of reversibly changing its light transmission in the visible region of the spectrum upon exposure to ultraviolet or short-wavelength visible radiation.

The photosensitivity of photochromic glass is caused by photochemical processes, which may be associated either with electron transfer between elements of variable valence—for example, EuII and CeIII—or with the photolysis of halides of heavy metals. In the case of photolysis, the halides are uniformly distributed as microcrystallites throughout the glass.

Glasses containing silver halides are the most widely used photochromic glasses because of their desirable photochromic characteristics—such as achieving a sufficient optical density upon darkening and rapid rates of darkening and fading—and technological properties. Photochromic glasses containing copper halides or thallium chloride are also used.

Photochromic glass may be a soda-lime-silica, borate, borosilicate, germanate, or phosphate glass. Photochromic glasses and the glasses used in technology are manufactured under the same conditions.

Photochromic glasses may be used, for example, in instrumentation as variable-transmission light filters, in construction to control lighting and heating in buildings, in holography as a medium for recording information, in medicine for special-purpose eyeglasses, and in aircraft and rocket manufacture for cockpit, cabin, or compartment windows.


Berezhnoi, A. I. Sitally i fotositally. Moscow, 1966. Tsekhomskii, V. A. “Fotokhromnye stekla.” Optiko-mekhanicheskaia promyshlennort’, 1967, no. 7.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Generally, the particle size of AgCl in photochromic glasses is less than tens of nanometers [6, 12].
Additive [Cu.sup.2+] ions acted as coloring and bleaching sensitizers in the AgCl photochromic composite films, which is different from the case of AgCl photochromic glasses. [Cu.sup.2+] ions in the composite film were reduced to [Cu.sup.+] by UV-vis irradiation, and the reducing speed was faster than that of [Ag.sup.+] to Ag.
10 Photochromic glass darkens according to light intensity; electrochromic glass changes in relationship to an electric current passed across it.