Natural Science in Archaeology

206 9 Pigments and Colorants
The nature of modern pigments is beyond the scope of this book. However, the
reader may want to become familiar with these if faced with the task of establishing
authenticity (Fleming et al. 1971). The presence of certain modern pigments in an
archaeological object could expose fraud. There are a number of excellent sources
on this topic including Painting Materials by Gettens and Stout (1966) and The
Particle Atlas by McCrone and Delly (Vol. 2, 1973). A table of pigments used in
antiquity is given in the Appendix A.
Colorants. The early use of colorants may have been accidental. Before methods
for glazing were known, ceramics were painted with earth pigments. The presence
of a fluxing agent in the paint or the accidental scattering of wood ash across the
ceramic surface during firing could have unintentionally caused a reaction with the
ceramic body, resulting in a vitrified and more durable colored finish. However,
until pyrotechnology had advanced sufficiently to control kiln temperatures, the
usefulness of this new technology would have been limited. If the flames touched
the object, color could be burned off or blackened, thereby marring the aesthetic
appeal of the ceramic surface. Eventually, advances in pyrotechnology allowed the
production of decorative colored objects including glazed ceramics and glass. The
understanding of oxidizing and reducing atmospheres in the kiln became especially
important for imparting color.
Although the precise origin of glass made by humans is not known, by 3000
BCE glass objects were being produced in the eastern Mediterranean (Newton and
Davison 1989). Early coloring agents may have been the result of natural contaminants
found in quartz sand. The most common contaminant would have been iron.
However, it was quickly discovered that the purposeful addition of naturally occurring
compounds could impart various colors to glass. The earliest contexts in which
manufactured glass have been found are Egyptian. Glass beads and small containers
were sometimes colored blue or red in imitation of semi-precious stones (Newton
and Davison 1989). These same colorants were found to produce similar results in
enamels and glazes used on ceramics.
The increase in the range of available colorants may have been contemporaneous
with the use of these same compounds in paint pigments. However, this is
not known for certain. As previously mentioned, smalt may have been used by the
ancient Egyptians in glass production, even though it was not known to have been
used as a pigment until its rediscovery by fifteenth century Europeans.
The ancient Egyptians are known to have used cobalt (blue or violet), iron oxides
(yellow), copper (red and bluish-green), and manganese (blue) as colorants in their
glass and ceramic glazes. They also used antimony as an opacifier to produce
“white” or opaque glass. The Romans used copper (red and blue) and cobalt (blue).
They also discovered that ferrous iron, which produced yellows and ambers under
oxidizing conditions, would produce blue in a reducing atmosphere. Iron oxides
could also be used to produce a black glass, although an excess of any coloring
agent may produce a similar effect (Newton and Davison 1989).
Soulier et al. (1996) report from their studies of the origin of cobalt blue pigments
in French glass from the Bronze Age to the eighteenth century CE that the
raw materials for four distinct chemical groups seem to have come from: group