DYES AND DYEING - Archaeological Chemistry - page 374

Murex trunculus snails. The dye is one of the components of a colorless secre-
tion produced by the Murex mollusks. When the secretion is exposed to
oxygen in the air and to solar radiation, it acquires color, turning first yellow
then green and finally purple. In the course of an investigation on the pro-
duction of Tyrian purple, only 1.4 g of the dye were obtained from about
12,000 mollusks! The coloring matter in Tyrian purple was identified in
the early twentieth century as the organic compound 6,6

-dibromoindigo
(Cooksey 2001; McGovern and Michel 1991, 1985). Because of the heavy
demand for purple and its high price, many substitutes, designed to either
dilute the dye or imitate its color, were used in the ancient world. Thus mix-
tures of indigo and other dyes that yield shades of purple were often used
as substitutes. At the time of the decline of the Roman Empire the manu-
facture and use of Tyrian purple seems to have subsided, being gradually
replaced by dyes easier to produce, such as archil, kermes, and madder. It
has been suggested that a purple dye similar in composition to Tyrian purple
was produced in the South American continent from the mollusk Purpura
patula Pansa (Doumet 1980; Saltzman et al. 1963).

″

Red Dyes

Quite a variety of red dyes of both vegetable and animal origin were used
in antiquity, although only a few of them ever attained practical importance.
Among these were madder , of vegetable origin, probably the most widely
used and in its heyday also the most important red dye, and kermes and
cochineal , both derived from the bodies of insects.
Madder, also known as Turkey red , is a scarlet dye extracted from peren-
nial herbaceous plants of the order Rubiacea , of which there are about 35
species (Chenciner 2001; Farnsworth 1951). A well-known plant from this
order is Rubia tinctorum , found naturally in Palestine and Egypt, abundant
in Asia and Europe, and extensively cultivated in the ancient world, was
widely used for production of the dye since remote antiquity. The use of
madder for dyeing seems to have originated in the Middle East: it was iden-
tified in many textiles found in Egyptian tombs and in woolen fabrics from
the Judean Desert in Palestine. It was also used by the ancient Persians,
Greeks, and Romans. Madder from other varieties of Rubiacea plants were
used by the Incas in ancient Peru (Schaefer 1941; Fieser 1930).
The dye is concentrated mostly in the roots of the plants, older roots
being richer in the dye than young ones. After removal from the soil the roots
are washed with water, dried, and chopped. The dye is extracted from the
plant tissue with hot water, in which it is soluble, but precipitates as a
powder when the solution cools down. The powder is then separated from