From Decolorization to Solarization of Historical Glass: A review

Abstract

Colour from raw material impurities is one of the main concerns for glassware production. Since ancient times until now, decolorizing glass, or making it clear, was a goal that had varying degrees of success from the 7th century BCE to the 1st century CE in the Mediterranean. A method for making glass clear was eventually systematized in Alexandria, under the Roman Empire, around 100 CE and spread through the empire. On the other hand Solarization refers to a phenomenon in physics where a material undergoes a temporary change in colour after being subjected to high energyelectromagnetic radiation, such as ultraviolet light or X-rays. Clear glass and many plastics will turn amber, green or other colours when subjected to X-radiation, and glass may turn blue after long term solar exposure in the desert. This paper aims to shed light on the studies and scientific literature of the decolorization and solarization phenomena of archaeological glass that until now has been recorded, but not extensively studied from the archaeometrical side.