Corrosion Phenomena Of Medieval Stained Glasses

Medieval stained glass windows have suffered from humidity for centuries. Increasing problems arose from environment pollution during the last decades. The high sensitivity of medieval glasses is caused by their chemical composition, the glasses show most severe damage at the outside surface. Corrosion crusts of up to several hundred microns in thickness and of different morphology can be found, consisting sometimes mainly of amorphous silica, sometimes of between 10-80% sulfates like gypsum and syngenite.