Natural Science in Archaeology

204 9 Pigments and Colorants
Hierakonpolis show the use of yellow, red, green, white, and black. In Meidum
and other Old Kingdom mastabas, this palette is completed with brown (hematite
mixed with soot), gray (gypsum mixed with soot), and two blues (azurite and blue
frit). During the 12th Dynasty, new green, red, and black colors are introduced,
but only one blue (Egyptian blue) is now used. From the 18th Dynasty onward,
yellow orpiment is introduced as well as more ochres and frits. A pink gypsum
stained with madder is an acquisition of Roman Egypt (Forbes III 1965). A new
white pigment on fifth and fourth century BCE Greek pottery has been shown to
be alumina (Al 2 O 3 ), probably the result of thermal decomposition of bauxite (Pérez
and Esteve-Tébar 2004).
The application technique can be very important in how a pigment behaves.
Certain techniques enhance the color of the pigment. Specifically, pigment grains
reflect less light when surrounded with a “vehicle”, and the color becomes more
“saturated”. “Paint reflects in proportion to the difference between refractive indices
of the pigment and the surrounding medium. The higher the refractive index
of the pigment and the lower that of the vehicle, the greater the light reflection,
and with white pigments, the greater is the resulting whiteness and hiding power.
There is also a close relationship between refractive index and color” (Laurie 1967).
In other words, there is a direct relationship between the technique of application
and the resulting optical effects. Therefore, the development of new and improved
application techniques constitutes an important aspect in the history of pigment use.
The ancient Egyptians used a tempera technique in which the pigment lay directly
on top of the wall surface (Lucas 1989). The adequate hiding power of a pigment
was crucial for the success of this technique.
The Greeks made a significant advance when they developed new techniques for
creating fresco paintings (Forbes III 1965). In fresco painting, the paint is applied
directly to wet lime plaster. As the plaster dries, the color chroma intensifies. This
is because a significant amount of shrinkage takes place in the surface, causing the
pigments to be drawn closer together over a smaller surface area. The reason that
the Egyptians did not develop this technique may be because they used gypsum
plaster, which does not exhibit a significant amount of shrinkage during the drying
process. An early example of the Greek use of the fresco technique can be found
at the Palace of Knossos, Crete. One of the pigments found at this site is Egyptian
Blue, which was probably procured through trade. The Greeks also employed a
technique known as “fresco secco”, which entailed mixing the pigments with lime
and water and applying the color to a dry ground (Laurie 1967).
Paints also could be applied to marble, limestone, wood, ivory, or metal. Wood
panels and ships were painted using pigmented waxes known as “encaustic” paints
(Pliny N.H. 35.3; 35.39; 35.61). Evidence suggests that the use of color on ancient
Greek structures, statues, and stelae was a common practice. The Parthenon was
reportedly painted with a polychrome scheme. This practice was apparently also
known to the Romans, but, unfortunately, little archaeological evidence remains.
Documentation for pigment manufacture during the Roman Period has survived
through the writings of Vitruvius and Pliny. Although Vitruvius sometimes confused
pigment names and techniques, his writings and those of Pliny have generally