Polychrome enamels, ceramics, glasses and their degradation

Abstract

International audienceDue to the good chemical stability of chemical bonds forming silicates, glass and pottery are generally well preserved and can be used as dating milestones. After a brief recall 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 the glassy materials (composition, mechanical and thermal characteristics, porosity, etc.) are presented and discussed in relation to corrosion resistance. The corresponding analytical techniques are addressed. Emphasis is given on the different mechanisms of degradation (surface and bulk corrosion, crazing/peeling, proton/water insertion, lixiviation, oxidation) as well as conservation and restoration practices. Dating/authentication of ancient artefacts by the measurement of Raman signal at the surface of glassy silicates is further presented