CHAPTER 12: Polychrome Enamels, Ceramics and Glasses and Their Degradation
Published:04 Jan 2021
Owing to the high stability of the chemical bonds that form silicates, glass and pottery are generally well preserved and can be used as dating milestones. After a brief overview of the preparation of (glazed/enamelled) pottery and glass (utensils, stained-glass windows) from the technical and historical points of view, the main chemical and physical characteristics of glassy materials (composition, mechanical and thermal characteristics, porosity, etc.) are presented and discussed in relation to corrosion resistance. The relevant analytical techniques are addressed. Emphasis is placed on the different mechanisms of degradation (surface and bulk corrosion, crazing/peeling, proton/water insertion, lixiviation, oxidation) and on conservation and restoration practices. Dating/authentication of ancient artefacts by the measurement of Raman signals at the surface of glassy silicates is further considered.