Vitreous materials are analysed to determine their nature and weathering status. These elements may be useful in the context of both authentication and preservation-restoration.
The composition of glass or enamel (chemical nature of the glass and any chromophore elements present) is frequently typical of a specific period or civilization. It may be determined using various techniques, depending on the accuracy required.
The main factors in natural degradation of glass are humidity, gases (generally in urban areas) and atmospheric dust, light, and changes in temperature.
The effects consist of leaching of certain compounds from the object's surface, the appearance of cracks, colour changes, crystal formation (soluble salts), clouding, etc.
Studies of vitreous materials are generally carried out using microsections to facilitate examination of phenomena inside the material and on its surface.
Optical microscopic imaging is used to determine the presence of any deterioration on the surface or inside the glass (cracks, surface discolouration, etc.).
Electron microscope examination coupled with EDX analysis is used to determine the major (>10%) and minor elements (1% - 10%) in the composition of the glass, and verify the nature of any leaching or neogenic crystals (soluble salts).
PIXE or WDX analysis is used to determine the composition more precisely, as well as to detect and measure the trace elements present in the material, which may sometimes be decisive for determining the origin of a glass sample.