Dyes and pigments

[Dept of PMM Artists & things]

Early uses

The dyeing of linen and leather in Mesopotamia and northern Syria and Egypt was being carried out as early as 2000 BC in temple workshops, where the sacred vestments for gods and priests were dyed. In Ancient Greece, dyeing was a state monopoly, but private dyeing took place, after the purchase of a dyeing licence. In Palestine, as in Syria, dyers were concentrated in certain towns. Complete information on the processes of dyeing is not available, although recipe books for dyers did exist in Ancient Egypt. The oldest known book on the subject is from the third century; this includes notes of an alchemist describing dyeing cloth with alkanet, safflower, saffron, kermes, madder and woad. Woad and indigo were used by the ancient Egyptians: dyes have been found on cloth of about 2500 BC and on later mummy wrappings, though they were apparently not in common or extremely use until 300 BC. In Hellenic times, vat dyeing of wool with indigo was commonplace. It was Caesar who described the native tribes of Britain as fierce warriors painted blue with woad; Britain takes its name from Celtic word brith meaning paint. The Greek herbalist Dioscorides also described the leaves as being astringent, which helped to stem the flow of blood. The detergents used in the dyeing process were contained in the roots of Saponaria officinalis L. (soapwort of the carnation family, Caryophyllaceae), a well known plant in ancient times. Natron and the root of asphodel were also used. The use of urine as a mordant for fixing woad and indigo is mentioned in about 200 BC describing the foul smelling hands of the dyer. The urine-vat is rarely used now, whilst the fermentation method is common in the East.

Woad was more commonly used in Western Europe as it grew widely in the region. The young leaves were milled to a pulp, made into balls and dried for a few weeks after which the mass was powdered and left to ferment with water until a dark colour was produced, after which it was put into barrels for storage or to be sold. When used, it was re-fermented in a heated vat and the cloth dyed. Because colour production from woad is laborious compared to production from indigo, indigo began to replace woad for production of in the sixteenth century.

The most highly valued, and noblest, colour of ancient times was purple. In general however, purple dyes were not of plant origin, but instead derived from molluscs such as Murex. But to obtain the prized purple colour, wool could be dyed blue by the Romans with indigo and then dyed again with some other dye that added a red colour, such as madder. There are also recipes for this process in early Egyptian papyri. After dying with indigo (or woad, there is some disagreement as to which blue was being used), ashes were scattered over the blue-dyed wool and trodden in by foot. The wool was rinsed and clay and pickled in alum (an important mordant). Finally the madder was dissolved, together with flour of beans (to soften the water) and the treated wool dyed for the second time.

The Egyptian papyri also mention that by using different mordants colour shades of blue produced by the use of indigo or woad could be varied.

Henna was a symbol of immortality and resurrection in Egyptian and Greek mythology and has been used as a cosmetic since ancient times. The ancient Egyptians powdered the leaves and made them into a paste that was then used by women (and men) to dye their finger and toenails. It was also used to dye hair and by men to dye their beards and moustaches, even for dying the manes and tails of horses. The dying of both toe and fingernails was a common practice, which has continued for a long time - as the nails of mummies have been found to have been dyed this way. The Egyptians are also thought to have extracted oil and made an ointment from the flowers for making limbs supple. The ancient Hebrews and Indians and people in northern Africa also used henna to dye the soles of their feet and palms of their hands. In Persia, men also used henna to dye their beards red, and then dyeing them black with a solution of indigo. Even children had their hair dyed red and it is said that Mohammed dyed his beard red with henna. Even today in Yemen, men who have made the pilgrimage to Mecca have red beards that have been dyed with henna. It is said that henna helps cool the skin, which may be why it came into use as a dye for the skin of palms of the hands in the way it did. The 'camphire' mentioned in the Song of Solomon in the Judeo-Christian Bible is probably henna, which was thought to have been introduced to Jewish women by Pharaoh's daughter when she became Solomon's wife. The fragrance of henna flowers was said in the Song of Solomon to be like that of roses.

Dyeing with madder or munjeet is a long process, and must take place slowly. The wool was worked for five hours in stages of alternate immersion and removal until the correct shade was obtained. In ancient Palestine, dyeing was a respected craft. Wool thread was dyed before being woven. Yarn was laid out to dry after dyeing and the surplus liquid expressed. Sometimes a bran mash was used as a mordant. Purple-dyed wool was stored in bags or wrapped in skins. The re-dying of indigo-dyed wool was also common in Palestine. Dyes were expensive: the Hebrew word for spices, which were also expensive, was the same as the word for dyes. In ancient and medieval times madder was also used for medicinal purposes, especially for amenorrhea (loss of menstruation).

Madder produces a variety of shades of red depending upon the mordant used. A very strong, non-fading red was developed in India and spread, from where it became know as 'Turkey red'. Its production involves some twenty separate processes using blood, oil and rancid fat, along with charcoal, animal dung of various sorts and the liquid contents of animal stomachs. It is not surprising that villages in which the industry was concentrated were inhabited solely by dyers and their families! The technique was imported into Europe in the eighteenth century (Turkish carpets were, before 1750, unique in having Turkey red in their make-up). In northern Europe madder production was a speciality of the Low Countries (Holland). In the eighteenth century in England madder was used for soldier's uniforms and for the classical pink coats worn in fox hunting.

Weld was described by the Greek herbalist Dioscorides as a classic yellow dye-plant. In the first century AD, the Roman historian Pliny said that weld was used exclusively for colouring women's garments. The use of other yellow dyes was discouraged in the thirteenth century, partly because it was thought to impart a permanent colour. In medieval times Jewish men were compelled to wear yellow caps through much of Europe, these were dyed with weld. Weld was used to make blue cloth green and when added to madder could produce an orange dye. It was used as a dye for cotton, silk, linen and woollen fabrics as well as calico-printers, colour-makers and wallpaper manufacturers. Gradually, the use of weld was superseded by use of black oak (Quercus velutina Lam.) from North America, which weight or weight produced a stronger yellow. Dyeing cloth first with weld (yellow) and then woad (blue) produced green, but boiling fabrics in a solution with verdigris and alum could also produce a green.

In medieval times, ink was produced from crushed oak galls, which contain much gallic acid and tannin and ferrous sulphate. Also used was carbon made from scorched vine-shoots, though getting the exact consistency and density was difficult. Medieval craftsmen had recipe books for making dyes, some of the information having been collected from Alexandria about AD 600 and translated into Latin 200 years later. Certain terms for dyestuffs are Arabic and Persian. There is an early medieval craftsman's manuscript from about 1130 written in Catalonia (near Barcelona in southern Spain) that contains many recipes for pigments, dyestuffs, inks, varnishes and glues. By medieval times many pigments and dyes were not made from plant products; for example green from copper plates packed in fermenting grape-skins, or but other greens still came from plant products.

The most common black dye in medieval times was produced by adding extract of galls to iron sulphate or to superimpose several dark layers of shades, one over the other, so that the density deepened layer on layer.

Any mixture of iron salts in alum gives darker shades, the preparation of pure alum became important, and hence the alum trade was very important from the earliest classical times until the end of the nineteenth century. alum is important historically as it is the first substance prepared in what was a pure state. This was not due to chemical knowledge but the resulted from the dependence of alum for its use on its freedom from irons salts making it valued as a mordant.