Solarization (physics)
Solarization is a phenomenon in physics where a material temporary changes color after being subjected to high-energy electromagnetic radiation, such as ultraviolet light or X-rays. For example, clear glass and many plastics may turn amber, green, or other colors when exposed to X-radiation, while glass can become blue after prolonged solar exposure in the desert. It is believed that solarization is caused by the formation of internal defects, called color centers, which selectively absorb portions of the visible light spectrum. In glass, color center absorption can often be reversed by heating the glass to high temperatures to restore the glass to its initial transparent state. However, solarization may also permanently degrade a material's physical or mechanical properties, and is one of the mechanisms involved in the breakdown of plastics within the environment.