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Natural Dyes

Natural Dyes. 

If you lived in England during the Middle Ages, your wardrobe was probably drab by today's standards. Your choice of colors was generally limited to blacks, yellow-browns and grays. Reds and purples did exist, but the supply of fast dyes in these colors was very, limited, and most of it was used for royalty and ecclesiastical garments. Then, shortly after the famous voyages of Columbus, the discovery of two remarkable trees from the New World forever changed the wardrobes of Europe and led to the birth of two nations.

Two popular animal dyes of this period were imported from faraway lands and were very expensive. Tyrian purple or royal purple was obtained from Mediterranean snails of the genus Murex. It was the principal dye of seafaring Phoenicians, and it was used to dye the robes of ancient Greek and Roman aristocrats. Carmine red was obtained from the crushed bodies of cochineal scale, small insects resembling mealy-bugs that live on prickly pear cacti of Mexico and the Southwestern United States. Known to the Aztecs and Spanish conquerors, the brilliant red dye comes from blood-red fluids of female insects. Each plump little female (which is practically legless) secretes a protective cottony mass around her body. By tedious hand labor, large numbers of the minute insects were brushed off cactus pads and exported to England. It took about 70,000 dried insects to make one pound of dye. The demand for cochineal was so great that the cactus host plant was introduced into Australia, with disa strous consequences. By 1925, 60 million acres of valuable range land were covered by prickly pear cactus. Finally, a Mexican moth, whose larvae feed on prickly pears, was introduced to clear away the cactus thickets. To this day, carmine stain is commonly used in bacteriology laboratories. Cochineal insects were reportedly used to dye the uniforms worn by British soldiers; however, most redcoats of the Revolutionary War were dyed with madder, a brilliant crimson dye from the roots of the madder plant (Rubia tinctorum) found in Southern Europe and Asia Minor.

Two of the most popular purple and red dyes in medieval Europe, orchil and cudbear, came from crushed, boiled lichens, especially Roccella tinctoria. Lichens are interesting fungus plants containing green, photosynthetic algae. Most fungus and algae live together in a symbiotic "marriage" which appears to be mutually beneficial -- at least for most lichens. In early days the dyes were dissolved in human urine and the cotton and wool yarns were immersed in this mixture. Ammonia salts in the urine functioned as mordants to make the dyes permanent. The action of mordants is complex, but essentially they serve to chemically bind the dye molecules with the fabric polymer. Other popular mordants included alum, cream of tartar and white vinegar. Lichen dyes often change colors in the presence of acids or bases. In fact, the litmus dye that turns red in acid solutions and blue in alkaline solutions is derived from a lichen (Roccella spp.). Although most of the lichen dye industry was replaced by cheaper aniline dyes from coal tar during the late 1800s, some lichen dyes are used today. A brownish lichen dye (from Parmelia omphalodes) is still used on hand-woven Harris tweeds from the Outer Hebrides. Orcein, a purple chromosomal stain found in every microbiology laboratory, is also derived from a lichen (Roccella tinctoria).

Saffron was the principal yellow dye used in medieval times.
It was derived from the elongate stigmas of the saffron crocus (Crocus sativus), an autumn-flowering plant of the Iris Family. Through tedious hand labor, four thousand stigmas were needed to yield one ounce of this precious dye. Today saffron is used for coloring medicines and food to which it imparts a characteristic flavor. Many Hindus apply a spot of saffron to their forehead as a "good omen."

Achiote or annatto (Bixa orellana), another popular food coloring, was once used to dye wool and calico goods. Achiote is a native shrub of Central and South America with bright red spiny fruits. The orange-red dye (bixin) comes from the outer covering of the seeds which is scraped off and made into a paste for shipment. Many South American Indians use the dye for body paint, a practice that may protect their skin from harmful ultraviolet radiation. (Ed. note - According to the Merck Index, 1989 ed., beta carotene, an ultra-violet screen, and bixin have a similar absorption spectrum.) Since bixin is closely related to beta carotene, the use of this dye to color food may also supplement a tropical diet with vitamin A.

For centuries indigo was considered to be the world's finest dye. Nothing had been found to equal the permanency and strength of its deep-blue color. Indigo was known to people of Asia as a dye and cosmetic for over 4,000 years. The name is derived from the Latin word indicum, originally used to define all imports from India and later specifically applied to a beautiful blue dye from India. Indigo was originally obtained from the leaves of a tall, weedy perennial of the Legume Family (Indigofera tinctoria). Freshly cut plants were steeped and beaten in vats of water until a blue residue formed at the bottom. In medieval Europe, the dark blue cubes of indigo residue were thought to be a mineral imported from mines of India. Curiously enough, the dye is not present in the plant itself. The leaves contain indican, a soluble colorless glucoside which oxidizes in water to form the blue insoluble precipitate.

The Venetian traveler and merchant, Marco Polo (ca. 1275-1292), was well aware of indigo from his extensive travels in Asia; however, the use of this dye in western Europe was very limited until an all-water route to India was discovered in 1498 by Vasco da Gama. Shortly after the discovery of America, Columbus also described Indians using a similar species of Indigofera native to the New World. At this time, another blue dye called woad was commonly used in Europe. It was obtained from the leaves of a tall herb of the Mustard Family (Isatis tinctoria). Growers, distributors, and dyemakers of woad bitterly protested the imported indigo, calling it "corrosive" and "the devil's dye." A local law in Nuremberg required dyers to take an annual oath that they would not use indigo.

For centuries indigo has been used to dye the uniforms of British and American sailors. The selection of blue apparently dates back to King George II and a meeting of British naval officers in 1745. The officers were directed to appear before the Admiralty, each wearing their favorite uniform. According to one story (described by William F. Leggett in Ancient and Medieval Dyes, 1944), an enterprising captain chose the blue colors used in the riding habit of the Duchess of Bedford, a favorite of the King, and who just happened to be the wife of the first Lord of the Admiralty!

One of the finest red dyes for cotton and wool during the Middle Ages came from the heartwood of an Asian tree called sappanwood (Caesalpinia sappan). The dye was a beautiful red, the color of burning coals (in Old French and English "braise") and was called bresil or brasil by the early Portuguese traders. In 1500, Portuguese ships discovered and claimed the Atlantic side of South America that straddled the equator and the tropic of Capricorn. This massive land was called "terra de Brasil" and later Brazil, because of the dyewood trees (Caesalpinia echinata) that grew there in abundance. Like the closely related sappanwood, the valuable dye from brazilwood (called brazilin) became a popular coloring agent for cotton, woolen cloth, and red ink. As with precious cargoes of gold and silver, Portuguese ships loaded with brazilwood were favorite targets of marauding buccaneers on the high seas.

Meanwhile, the Spanish had discovered another tree in Yucatan with a deep red heartwood very similar to brazilwood. The tree became known as logwood (Haematoxylum campechianum), and by the late 1500s Spanish ships were exporting large cargoes of the valuable heartwood from the Yucatan coast.

The actual dye from logwood is called hematoxylin, with a chemical structure practically identical to brazilin. Hematoxylin is extracted by boiling chips or raspings of logwood in water. Through oxidation the hematoxylin is converted into another dye called hematein. Logwood dyes have been used extensively for cotton and woolen goods, leather, furs, silk, and inks. In order to make the dyes colorfast, they were used with various mordants. Different colors were produced, depending on the type of mordant and duration of the dye bath, including permanent blacks, bright reds and beautiful shades of blue, lavender and purple.

Many English dyers vigorously opposed the cheaper, imported heartwood dyes from Mexico and Central America. They preferred to use carmine, madder, and indigo, and the well established lichen dyes. Between 1581 and 1662, an Act of Parliament strictly forbade the use of logwood for dyeing. Although anyone violating this law was subject to imprisonment or the pillory, some dyers apparently discovered the colorfast attributes of logwood and used it under other names.

The fame of logwood spread and soon British privateers began capturing logwood-laden vessels on their voyages back to Spain. When the Spanish Navy sent expeditions (ca. 1600-1640) to protect the logwood ships, crews of the privateers began searching for logwood on shore. By this time, the British had discovered large stands of logwood on the Caribbean shores of Central America. By the late 1600s logging camps were established in the mosquito-infested swamplands which became known as British Honduras, and later as Belize. The early wood cutters, called Baymen, exported thousands of tons of logwood back to England. To this day, a black and a white logwood cutter are depicted on the flag and currency of Belize.

Most of the natural dyes of Europe have been replaced by less expensive aniline dyes derived from petroleum. Kings and clergymen no longer wear robes dyed with lichens, logwood, and Tyrian purple; and British soldiers no longer wear uniforms dyed with madder root. However, bottles of orcein, carmine red, and hematoxylin will probably always be around on the shelves of microbiology laboratories and on the workbenches of fine woodcrafters. The days of rugged buccaneers and Baymen have long since passed; their marvelous masted ships no longer ride the ocean currents and trade winds back to England. But the memories of those fabulous times are forever commemorated in two nations that literally owe their births to dyewood trees.

References
Buchanan, Rita (Editor). 1990. Dyes From Nature. Brooklyn Botanic Garden, Brooklyn, NY.
Liles, Jim N. 1990. The Art and Craft of Natural Dyeing. University of Tennessee Press, Ithaca, NY.

by Wayne P. Armstrong
HerbalGram. 1994; 32:30 American Botanical Council

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