Cochineal, Saffron & Woad Photos

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Economic Plant Photographs #3

Madder, Cochineal, Saffron, Woad, and Alkannin

1. Madder Family (Rubiaceae):

Several natural plant dyes were used for the classical colored clothing worn by historical figures. For example, the red coats worn by British soldiers during the American Revolutionary War were colored by a crimson dye from the roots of madder (Rubia tinctorium), a member of the madder or coffee family (Rubiaceae). Madder is a perennial herb with leaves in whorls of 4-5 or more at the nodes. A related and similar-appearing weedy species in California is called bedstraw (Galium aparine), so named because bunches of the plant were used like straw for bedding. The famous gray coats of the Confederate Army in the Civil War were colored with a dye from butternuts (Juglans cinerea) of the walnut family (Juglandaceae). Another natural dye used by ancient Greek and Egyptian women to color their hair reddish-brown was obtained from the leaves of henna (Lawsonia inermis) of the loosestrife family (Lythraceae). Because of its affinity for protein, henna is still used to this day as a hair rinse.

Left: Madder (Rubia tinctorium), a European perennial and source of the red root dye called alizarin. Right: Bedstraw (Galium aparine), a common California weed in the madder family with whorled leaves at the nodes like madder.

Madder (Rubia tinctorium), a Mediterranean perennial with square stems and whorls of 4-5 prickly leaves at the nodes. Retrorse barbs along the stem make it cling to your clothing, like species of bedstraw (Galium) in southern California. The flowers are small, greenish-yellow and inconspicuous.

To make some of these natural clothing dyes colorfast (so they wouldn't wash out of the fabric), it was necessary to use various mordants such as mineral salts of tin, aluminum, iron and chromium. In ancient times these mineral mordants came from the metal vessels in which the dyeing was done. In some cases, mordants were added to the dye mixture, including urine and dung. It is a well-known fact that ammonia from urea makes an excellent mordant for certain dyes. Chemically, the mordant helps to bond the dye molecules to the fiber molecules of the fabric. The actual bonding of classical dye molecules with the cellulose polymers of the fiber involves complex hydrophobic interactions and hydrogen bonding. Madder is a particularly good dye because it contains natural mordanting agents. During the Middle Ages, people who made and dyed hats (called hatters) often used heavy metals in their dye baths as mordants. Because they did not wear protective gloves, some hatters absorbed toxic levels of heavy metals causing them to become mentally deranged; hence, the term "mad hatter."

Just as the printing industry was replaced by computers, the dyeing industry was revolutionized by the discovery of synthetic dyes. During the latter half of the 19th century, synthetic dyes were being produced from derivatives of coal tar (from high temperature carbonization of bituminous coal). These dyes (called aniline dyes) produced a wide array of vibrant colors that were much more colorfast than even the best natural dyes. There are, however, many people today who still prefer natural dyes because of health concerns about the safety of synthetic dyes, particularly if they are ingested or come in contact with sensitive areas of the skin.

2. Cactus Family (Cactaceae):

The cochineal insects on this cactus pad are covered by a protective cottony mass which they secrete. They belong to the order Homoptera and are related to aphids, scale insects and mealy bugs. Female cochineal insects are brushed from the cactus pads, dried, and the bright red pigments are extracted from the dried bodies. One pound of dye represents about 70,000 insect bodies. Cochineal-laden cacti were introduced into Australia for this valuable dye with disastrous consequences. By 1925, 60 million acres of valuable range land was covered by prickly pear cactus. A bright red dye and the biological stain carmine used in microbiology classes is made from the crushed bodies of these unusual insects. The washcloth in the photo was dyed with cochineal; however, without the proper mordants it will wash out and fade rapidly. Note: To control the spread of prickly pear cactus in Australia, the cactus moth (Cactoblastis cactorum) was introduced, and by 1930, thanks to the voracious larvae, vast areas of cactus scrub had been denuded; however, this method of biological control has raised havoc in other areas of the world due to "nontarget effects." The moth has attacked other species of cacti, some of which are rare and endangered.]

According to Thomas Eisner et al. (Science 30 May 1980: Vol. 208 no. 4447, pp. 1039-1042), carminic acid, the dye from cochineal insects, is a potent feeding deterrent to ants. This may have evolved as a chemical weapon against predation. The carnivorous caterpillar of a pyralid moth (Laetilia coccidivora) is undeterred by the dye and feeds on cochineal insects. In fact, the moth has the remarkable habit of utilizing the ingested carminic acid for its own defensive purposes.

A well developed infestation of cochineal insects (Dactylopus coccus) on a cactus pad in San Diego County. Several plump females (red arrows) have given birth to tiny white nymphs. The nymphs and adults are concealed by a protective cottony mass secreted by the adult females. The bright red body fluids are the source of cochineal dye.

Plump adult female cochineal insects (Dactylopus coccus). A. Adult partially covered by cottony secretion. B. Adult covered by cottony mass and red body fluids, the source of cochineal dye. C. Adult female with most of cottony secretion removed.

Plump female cochineal insects (Dactylopus coccus) that have just given birth to several tiny nymphs. Externally, these insects resemble a wrinkled ball with vestigial, nonfunctional legs and reduced mouthparts. Adult insects are concealed by a protective, cottony (waxy) mass that is secreted around the red bodies. They are not readily seen unless the insect's body is crushed, when the red body fluids seep out into the cottony mass. The bright red body fluids are the source of cochineal dye.

See Article About Prickly Pear Cactus

Good References About Cochineal Insect:

  1. Donkin, R. A. 1977. "Spanish Red: An Ethnogeographical Study of Cochineal and the Opuntia Cactus." Transactions Of The American Philosophical Society 67 (Part 5): 1-84.

  2. Greenfield, Amy Butler. 2005. A Perfect Red: Empire, Espionage, and the Quest for the Color of Desire. HarperCollins Publishers Inc., New York.

  3. Stiling, P. 2000. "A Worm That Turned." Natural History 109 (5): 40-43.

3. Iris Family (Iridaceae):

The ancient yellowish-orange dye saffron is produced from the crushed stigmas of autumn crocus blossoms (Crocus sativus). The coloring principle is crocin, a tetraterpene carotenoid pigment related to vitamin A. It takes about 4,000 stigmas to yield one ounce of the dye, and one part of commercial saffron is sufficient to color 10,000 parts of water. Although very costly, the red stigmas of saffron were used to dye the robes of Irish royalty centuries ago. To this day, saffron is still used as a popular (and expensive) food coloring and flavoring. It is also used in pharmaceuticals and in perfumes.

4. Mustard Family (Brassicaceae):

One of the most interesting natural blue dyes comes from the leaves of a wild mustard called woad (Isatis tinctoria). Woad was introduced into the United States from Europe during colonial times. It is a widespread and colorful, biennial or perennial herb that has become a naturalized weed in some states. In fact, there is some speculation that early German names for woad (weedt, etc.) may have given rise to the modern word "weed." Although true indigo (Indigofera tinctoria), a member of the legume family (Fabaceae), was perhaps a superior blue dye, woad continued to be a popular blue dye in Europe. [Indigo was an extremely important trade item between India and other parts of the world for thousands of years.] Actually the active dye ingredient of woad is the soluble glucoside indican, the same dye found in the unrelated indigo. According to the textbook for this course Plants In Our World by B. B. Simpson and M. C. Ogarzaly (1995), woad was one of the dyes used to make the green outfits worn by Robin Hood's men deep in Sherwood forest. Their clothing was dipped in a blue dye bath of woad, and then in a bath of yellow weld from the leaves of Reseda luteola, a member of the mignonette family (Resedaceae). The mixture of blue and yellow produced the characteristic green color associated with England's legendary bandit who robbed from the rich and gave to the poor. Apparently, the fermented, pulpy masses of woad leaves produced such a foul stench that early woad dyers were prohibited from heavily populated urbanized areas. In fact, Queen Elizabeth I (1533-1603) decreed that no woad processing could take place within five miles of her residence.

An open field of woad (Isatis tinctoria) in Eastern Oregon. Like other introduced mustards, this species produces spectacular displays of color during the spring and summer months. Although the winters in eastern Oregon are quite cold, this naturalized weed from Europe survives very well in this climate.

5. Borage Family (Boraginaceae):

Another little-known red dye called alkannin (also spelled alkanet) come from the roots of dyer's bugloss (Alkanna tinctoria). Alkannin is a deep red phenolic dye that is soluble in oils, alcohol and ether but not in water. Several members of the Boraginaceae contain alkannin, including dyer's bugloss (Alkanna tinctoria). It was used to dye textiles, vegetable oils and wine, and is commonly used today as a food coloring. In addition, it reportedly has wound healing and anti-inflammatory properties.

6. Brown Dye From A Fungus

Old sporocarp of dead man's foot (Pisolithus tinctorius) in the Palomar College Arboretum. David Arora (Mushroons Demystified, 1986) describes this fungus as follows: "This dusty montrosity is among the most distinctive and memorable of all the fleshy fungi." Older specimens in powdery stage resemble a brown stump and the mass of dry spore dust coats everthing in the vicinity. This is a beneficial, mycorrhizal fungus often attached to the roots of nearby trees.

Close-up view of the interior of an old sporocarp of dead man's foot (Pisolithus tinctorius). The dark viscous mass is the source of a brown dye. Spores are produced inside small peridioles the size of rice grains.

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