solarization (glass) en

The alteration of the light transmission characteristics of glass as a result of prolonged exposure to visible or ultraviolet light. Deterioration can be evident as a change in the color of the glass due to a reaction between the iron and manganese oxides in the glass initiated by light. This irreversible alteration can be a deep purple color, but is more often a subtle change in hue to pink, violet, or yellow. Solarized glass most commonly seen is pink to violet because it contains manganese. Since at least the 2nd century BCE, manganese has been used as a glass decolorizer to diminish the greenish hue imparted by trace amounts of iron. However, with exposure to ultraviolet light, manganese can photo-oxidize to reform manganese dioxide which is violet in color. From the 20th century, seleium and cerium have also been used as decolorizers; when photo-oxidized they impart a yellow to golden hue.