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Introduction to Dyestuff Class- T.Y.B.Sc. Prof .G.J.Korane Associate Professor M.P.A.S.C. College Panvel. Dist- Raigad. Introduction.
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Introduction to DyestuffClass- T.Y.B.Sc. Prof .G.J.Korane Associate Professor M.P.A.S.C. College Panvel. Dist- Raigad.
Introduction • Dyeing of fibers has been carried out since antiquity. Virtually every culture has its own set of dyestuffs, but a few have emerged and have been particularly important. • The majority of natural dyes are from plant sources: roots, berries, bark, leaves, and wood, fungi, and lichens.
Although these dyes were once widely used, the synthesis of synthetic dyestuffs in 1856 by William Perkin, an English chemist, and the subsequent manufacture of synthetic dyes (mainly by the Germans), replaced almost all of natural dyes with better quality materials. • Synthetic dyes are more stable, many bind more effectively to the fabrics, and they are more reproducible. • Some purists still use natural dyes, but except for food and histological uses, few of them are important.
Several dyes from animals have also been used. Cochineal (Coccus cacti) is a scale insect that feeds on cacti. It was used by the Aztecs. • A related insect from the Middle East produces a similar dye called kermes.
Adherence of dyes • Dyes must adhere to the fibers or they will be washed out. It is easier to dye animal fibers than plant fibers. • Although many plant parts are colored, the components of some of these parts are not particularly stable and decompose too quickly to be useful. Some do not bind well to the fibers. • In some cases, the dyestuffs bind tightly by chemical bonding and in others they are only bound by hydrophobic interactions.
Mordants • As early as the Egyptians, it was known that other substances caused some dyes to bind that normally would not. These are called mordant. • Many mordant's are metal salts that appear to form metal bridges between the dye and the fiber molecules.
Sometimes mordants came from the container in which the dyeing was being done and at other times from dung, urine or other compounds added. • Some dyestuffs (such as madder) contain substances that naturally act as mordants. • Alum is a commonly used mordant. Cream of tartar, wood ashes, tannic acid (sumac), and many other substances have been used.
Woad, Isatis tinctoria, Brassicaceae • Woad (Isatis tinctoria, Brassicaceae or Cruciferae) was once widely grown and utilized as a dyestuff in Europe. • Woad contains a smaller amount of the same compounds as found in indigo (actually these compounds are found in a number of other plants as well).
The odors produced from processing woad were legendary. The leaves were crushed and made into balls which were then allowed to ferment. After fermentation, the product was allowed to dry and then refermented before use to make it soluble. • In the Middle Ages, woad was a common article of commerce in Europe.
Indigo (Indigofera tinctoria, Fabaceae) • Indigo (Indigofera tinctoria, Fabaceae) has been one of the most important dyestuffs; this dye was used as far back as 6000 years in China. • Indigo produces an intense deep blue color. The leaves and branches of the plant are harvested, placed in a vat, covered with water, and permitted to ferment.
Indigo, Indigoferatinctoria, Fabaceae R. Bentley and H. Trimen, Medicinal Plants, London, Churchill, 1880
Indigo, Indigofera tinctoria, Fabaceae Courtesy Dr. David Rembert
The sludge of partially rotted plant material which settles to the bottom is collected and pressed into cakes. • When dry, these cakes produce a powder that makes a colorless solution. • The color only develops when an item is dipped into the solution, removed and then exposed to air.
Natural Dyes • Indio Dye • Madder Dye • Henna • Logwood • Curcuma Longa ( Turmeric)
Indigo Dye • Indigo dyeing and the cultivation of the plant originated in India. Because of the good quality of the dye, indigo became an important item of trade between India and other parts of the world by 300 B.C. • Dyers in Europe tried to resist the importation of indigo into Europe and were able to do so for a long time. Finally, however, quality won out. • Although indigo of commerce came from an Old World plant, another species of Indigofera was domesticated and used as a source of a blue dye by the Precolumbian inhabitants of Yucatan.
Indigo was an early crop in colonial South Carolina. South Carolina indigo was considered excellent, but as the economics were not too good, it was replaced by rice. • The leaves contain about 3% indigo. • Synthetic indigo was produced in 1897.
Baptisialeucantha, false indigo, Fabaceae In the Eastern U.S., Indians sometimes used Baptisia species, which also contain indigo, as dyestuffs.
Madder (Rubia tinctoria, Rubiaceae) • Madder (Rubia tinctoria, Rubiaceae) (see p. 372) has been used since ancient times. • One form of this dye is sometimes called Turkey red. • The dyestuff is found in the root of the plant. • The compound in the plant is ruberythric acid. • Alizarin (a compound derived from madder) is usually used with an aluminum mordant.
Madder Dye • Madder is locally important in the Near East and indigo is still used in Africa and India.
This dyestuff is fast to water and light. • Madder was formerly used to dye mummy blankets in Egypt. • Although the dye is fast, the dyeing process is complicated. • The fibers were covered with cheap vegetable oil (called Turkey red oil), were then degreased and treated with tannic acid, followed by a aluminum mordant. The fibers were then steamed.
Changing the mordant can give red, pink, lilac, orange, black, and brown colored pigments. • This dye was introduced into Europe in the late Middle Ages. • The Dutch selected lines that were of superior quality. • The color of the British soldier's uniform in the Revolutionary War was produced by madder. • Alizarin is still used as a biological stain.
Henna (Lawsoniainermis, Lythraceae) • By 3000 B.C., Greek women used henna (Lawsonia inermis, Lythraceae) to dye their hair. The leaves are ground into a paste that has a great affinity for protein. • Henna is still used in hair preparations.
Safflower (Carthamustinctorius, Asteraceae or Compositae) • Safflower has been used as a dyestuff for thousands of years in India and other parts of the Near East. • Probably native to Afghanistan and Pakistan. • Makes a red or yellow fugitive dye. • Today grown mostly as an oilseed.
Logwood (Haematoxyloncampechianum, Fabaceae) • Logwood (Haematoxylon campechianum, Fabaceae) came from the New World. • The wood of this tree permitted dyeing things black for the first time. • Although not used today for dyeing, haematoxylon stain is used as a histological stain in blood analysis.
Curcurma longa (Turmeric) • Turmeric (Curcurma longa, Zingiberaceae) is used mostly today to color foods (such as pickles), but has been used to dye clothing.
