The use of organic and chemical dyes and dying allows yarns and fabrics to be produced in virtually every color, tint and shade. Although they have now largely been replaced by chemical dyes, organic dyes were in use for over 2000 years until the late nineteenth century. It is not known when the first organic dyes were used, because dyes and dyed fabrics rarely survive as archaeological remains.
Indigo, which is bluish, has been found on Egyptian cloth dating from about 250 BC.
The indigo plant is Indian in origin and may have been used as a dye there before its first use in Egypt. Woad was used in Europe to produce blue coloration until indigo, with its greater dye yield, began to replace it in the fifteenth century. The woad plant is native to south-west Asia and was well known as a dye in Egypt and Mesopotamia by 300 BC.
In south-west Asia, a red dye was obtained from the dried and crushed bodies of the female scale insect Coccus ilicis, which infests the kermes oak, found in abundance in Mediterranean countries. The dye, known as kermes, is one of the most ancient dyes and was known to the Assyrians at least 3000 years ago. The kermes insect is related to the cochineal insect, native to Mexico, which produces the red dye known as cochineal. Cochineal rapidly replaced kermes as a red dye in Europe from the mid-sixteenth century. Madder, another plant yielding a red dye, has been cultivated for at least 2000 years. The madder plant is native to south-west Asia and was used in Egypt, Syria and Palestine; it is also believed to have been used in the Indus Valley about 3000 years ago. Madder was the most important red dye in Europe during the Middle Ages and remained in general use until the late nineteenth century, when a chemical substitute was found.
The most highly prized of the ancient dyes was extracted from the molluscs Purpura and Murex, found on the coast of the eastern Mediterranean from Tyre to Haifa. The purple dye that they yielded was expensive, because only a small part of the mollusc was used and the dye was difficult to extract. It was mostly used in dyeing fabric for the tunics of the emperor and other high officials of the Roman empire.
Yellow dyes can be obtained from a wide range of plants and are perhaps the easiest of all natural dyes to extract. Two kinds of wood used for yellow dyes are known as fustic; 'young' fustic, or Venetian sumac, has been in use for longer than, and is unrelated to, 'old' fustic, which belongs to the mulberry family. Weld or dyer's rocket was used as a source of yellow dye from prehistoric times and was collected by the Neolithic lake dwellers of Switzerland. Saffron and tumeric are plants used both as a source of yellow dye and as coloring and flavoring spices in cookery. Saffron has always been a very expensive dye, because it requires about 4000 stigmas of the saffron crocus flower to obtain 1 ounce of dye.
Green is the hardest color to obtain from organic dyes and, in most cases, fabrics were first dyed yellow and then blue. The English Lincoln Green, traditionally said to have been worn by Robin Hood, was obtained by dyeing fabric with the two dyes, weld and woad.
Although craft dyers of today still use the ancient dyes, many also use common plants, such as marigolds, onions, rhubarb and privet berries, as dyes. The process of dyeing with organic dyes varies according to the plant used. Indigo was originally produced by fermenting the plants, rendering the resulting solution alkaline, and collecting and drying the blue sludge that was precipitated. Cochineal and kermes are more simply prepared, involving only the collecting, drying and crushing of the insect and boiling of the powder in water. Most organic dyes require a mordant to fix
them to the fabric and prevent fading. Such substances are acid or alkaline and form a chemical bond with the dye; alum is the most common mordant. Mordants can be applied to the fabric before dyeing or mixed with the dye in the dye-bath. Some mordants also affect the color of the dye, and a range of colors can be obtained from one dye by using different mordants. The dye is normally boiled in water and the fabric is then added and boiled until the desired shade is obtained.
Chemical dyes began to replace organic dyes in the late nineteenth century. The first synthetic dye was accidentally discovered by an Englishman, William Perkins, while he was attempting to synthesize quinine from coal tar derivatives. The dye produced a brilliant mauve shade on silk and did not wash out or fade. After aniline purple, as the dye was known, many other aniline (coal tar based) dyes were produced and, by the end of the nineteenth century, synthetic substitutes had been found for all of the organic dyes. Most chemical dyes are applied to fabric in solution with water, which is steam heated under high pressure. Some require mordants to fix them to fabrics, but many are substantive, or self-fixing.