Chapter 7 Glass and Ceramics
HANNELORE RÖMICH
Fraunhofer-Institut für Silicatforschung (ISC), Bronnbach 28,
97877 Wertheim-Bronnbach, Germany
1 INTRODUCTION
Glass and ceramics are two materials that appear rather different at first sight:
glass is appreciated through its transparency, whereas ceramics are opaque
materials, more related to earth than to light (see Figures 1 and 2). Even if we
look at their structure and degradation mechanism, there are fundamental dif-
ferences: glass is a dense material reacting only on the surface, with water as
the principal aggressive agent, whereas ceramic objects are oftenendangered
by salt precipitation within their porous structure.
The links between the two are to be seen first in their chemical composi-
tion, both being related to silicates, and second in their production process,
emphasising their importance for art and archaeology. Ceramics, the older
Figure 1A stained glass window from Cologne Cathedral, 16th century
(Picture provided by Dombauhuette Koeln, Germany.)