weathering

Weathering is the process by which glass deteriorates due to environmental factors, primarily water. The composition of glass is crucial; for instance, Roman soda-lime-silica glass is durable, while medieval potash glass is unstable. Water, especially when acidic, leaches alkali from the glass network, causing stress, microfractures, and a cloudy appearance known as "crizzled" glass. This process can also create an opalescent, pearlescent surface.1

Glass is brittle and can shatter under impact or crack from thermal shock. Another form of deterioration is solarization, a color change caused by light reacting with iron and manganese oxides within the glass. To preserve glass, protective coatings and environmental controls like double-glazing for stained glass can be used.1