Energy Saving Dye

Scientists at Oregon State University have developed a blue pigment. Mas Subramanian and his students have this to their credit. The dye is environmentally friendly and nontoxic. This is good news, because many inorganic blues are toxic or cause cancer, such as Prussian blue, cobalt blue, or ultramarine blue.

There is yet another property this dye possesses. It reflects light from sunlight especially in the infrared (heat) part of the spectrum. It is about 40% higher in reflectivity than most blue colors. This could prove to be ideal for paints used on cars, roofs, and other applications where keeping cool is desirable.

This will help in reducing the amount of energy consumption in cooling the vehicles as lesser air conditioning wil be required because it will reflect away much of the heat from the falling light. Because the paint is reflecting much of the energy, it tends to last longer as it is not broken down by the absorbed energy.

The compound was discovered by chance in the laboratory when a student heated a sample of manganese oxide (which is black) to 2,000 degree F. When it came out of the oven, it had been transformed into a bright blue color.

Subsequent analysis showed the compound had a trigonal bipyramidal structure—the shape of two pyramids pointing in opposite directions and joined at a triangular base. The central manganese atom is surrounded by five oxygen atoms. But other compounds—yttrium oxide and indium oxide—are required to stabilize the blue crystals.
Another application wil be paint the roof tops with this dye and save much energy.

Cochineal Red: The Bright Red Dye

In the ancient world of the Aztecs, red dye was considered more valuable than gold. The dye is made from the dried female cochineal beetles. Beetles were collected by hundreds of subjects combing the desert in search of its source. A pound of water-soluble extract required about a million insects, just as back in the days of the Roman Empire, a pound of royal purple dye required four million mollusks.

After the arrival of Cortez in the 1500s, the Spaniards traded the dried remains of this insect as a colorant that dyed items a brilliant crimson. Cochineal red was a stronger dye than ever before – and a color that no one could duplicate. Europeans used it for fabrics and illumination in addition to cooking since it is natural dye.

In the years that followed, great painter Michelangelo used it in paintings. The British used it for redcoats and the Canadians for their Mounted Police coats. It is thought that the first U.S. flag made by Betsy Ross had cochineal red stripes.

With the advances in chemistry of dyes, nowadays synthetic dyes have replaced almost all the natural dyes which were very labor intensive and involved growing of particular plants like indigo plant in India and insects. Synthetic dyes have more shades and are cheaper.

English: Breeding of the Cochineal (Dactylopiu...

Today, less expensive aniline dyes have replaced it, but it is used as a food coloring and is approved by the FDA as a natural colorant for food, drug and cosmetics. In fact, some brands of fruit juice use this red bug juice as a colorant.

The story of Cochineal red is even more fascinating. Europeans were never told of its insect origin. In reality, the insect looked so much like a seed, that the Spaniards traded it as grain.

Vegetable Dyes

Third most important group of dyes is the Vegetables dyes group. Although they can be obtained from almost any plant but most important were madder, woad, and indigo.
Madder (Rubia tinctorum),

Madder Plant

a bright red dye, comes from a plant of the same name also known as “dyer’s root.” Though its origin is lost in antiquity, it was used to dye the wrappings on Egyptian mummies. It is said that Alexander the Great used madder to help him defeat the Persians in 350 B.C. He had many of his soldiers dye their cloaks with splotches of red and stagger onto the battlefield. As the jubilant Persians fell on the “badly wounded” enemy, they were soundly defeated. Madder appeared in Europe in the seventh century and was the dominant red dye for more than 1000 years. It provided the red for the famous British redcoats during the American Revolution. The chemical responsible for the color is alizarin.

Woad, a dye from the European plant Isatis tinctoria, has been found on some of the most ancient textile fragments ever unearthed.

It was used to dye the robes of the high priests of Jerusalem in Biblical times, but it was in Europe that it was extensively cultivated. The dye was obtained by first air-drying the woad plants and grinding them to a powder. The powder was then moistened, placed in a warm, dark place, and stirred frequently. Several weeks of fermentation produced a black paste, from which a blue dye was extracted. The European woad plant had indigo as its main chemical constituent. Woad was the principal European dye for centuries, and dyers became quite skilled at mixing it with other dyes to obtain new colors. Saxon green was the result of dyeing a fabric with woad, then over dyeing it with weld, a yellow dye from another plant. When woad was over dyed with madder, a purple shade resulted.
Indigo, from the plant Indigofera tinctoria, is much richer in the indigo molecule.

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This dye worked its way from India to Egypt, the Holy Lands, and eventually Europe, where it arrived around 1200 A.D. Its introduction was bitterly opposed by woad growers. Many laws were passed against use of the “devil’s dye,” and it was widely believed to harm both the cloth and its wearer. So successful was the anti-indigo lobby that the dye did not become established in Europe for more than 500 years. Then King George II chose indigo for the British naval uniform, giving the world “navy blue” forever after. Indigo was one of
the few natural dyes of commercial importance to America. In 1744 Eliza Pickney grew indigo from seeds her British army officer father brought from the East Indies to the colonies. Later, the enterprising young woman persuaded plantation owners around Charleston, S.C., to grow indigo and set up the Winyah Indigo Society. This cooperative shipped great quantities of the dye to England, until introduction of synthetic indigo destroyed the market for the natural product. Today indigo has been largely replaced by other blue dyes, though it is still used as the dye of choice for coloring blue jeans.

More of Dyes: Animal Dyes

As told previously, the dyes were made from the minerals and natural rocks. The examples of these were Ochre Dyes which are the iron oxide compounds.

Second group of natural dyes is the animal group. One of the earliest and most important of the animal dyes called Tyrian Purple was obtained from several species of snails found along the shores of the Mediterranean.

Plicopurpura pansa

It was discovered by the Phoenicians about 1500 B.C. and became, for the next 3000 years, the most important dye of the civilizations that rose and fell in the area. The demand for mollusks rose rapidly as dye factories sprung up along the Mediterranean and west African coasts, and Phoenician traders carried the dye to Spain, France, and Italy. According to Pliny the Elder, the dye was extracted by crushing the shellfish and boiling them in salt water for ten days. Cloth was dipped in this solution, then exposed to sunlight. Due to the photosensitive nature of the coloring molecules, the yellow color changed to greenish-blue, then finally to purple. The Roman emperors prized the dye and decreed that only members of the royal family could wear clothing colored by it, hence the expression “born to the purple.” Among those who wore Tyrian purple were Alexander the Great, Julius Caesar, and Cleopatra.
Other animal dyes were obtained from insects. Kermes was a scarlet dye obtained from Coccus ilicis, a tree scale that lived on oak. Moses mentioned its use in Egypt, and other writers referred to it as captured booty in 1400 B.C. Kermes varied in color from bluish-red to brilliant scarlet depending on the mordant used. A mordant is cation of metal which forms a link between the clothe and the dye and helps adhere permanently to the clothe. It can also change the color of the dye altogether. One example of the mordant is Alum which contains Aluminum ions in trivalent state.

A dye very similar to kermes was discovered by Mexican dyers around 1000 B.C. Cochineal is derived from another scale insect, Dactylopius coccus, that lived on cactus. The insects were collected by hand, about 200 pounds per acre of cactus, and dried in the sun. The dried insects resembled rust-colored grain seeds and gave scarlet dye when soaked in water. The Spaniards learned of cochineal in 1518 A.D. and brought it to Europe, where it rapidly replaced kermes. The scarlet obtained with a tin mordant is particularly beautiful and was used until 1954 to dye the uniforms of the British Brigade of Guards uniforms.

Dried Insects

Henna

It is natural dye derived from green henna leaves and is used to decorate the body with intricate designs in India and Pakistan. The hands and legs of the brides and her friends are adorned with intricate designs using a paste made from ground henna and juice of lemon. Motifs include birds, animals and geometrical patterns.

aupoman-hk-henna-tattoo-hand

Application of henna causes a cooling effect. It is also a fact that longer this stays on the hands more is the color darker. So after application to prevent the paste from flaking off, small amounts of lemon juice and sugar are applied. Usually after the night, it dries off. It is scraped off and hands are washed leaving behind an auburn colored dye designs on the body. It stays there for many days.

The paste is prepared from the green leaves of Lawsonia inermis, a small tree that grows in warm, arid regions of the world such as India, Pakistan, and Northern Africa. Numerous artifacts found in Middle Eastern and Mediterranean countries, dating back to 1400 B.C., show women with henna patterns on their hands. The earliest writing on an artifact that refers to the specific use of henna as an adornment for a bride or a woman’s special occasion is an inscription on a tablet from about 2100 B.C. found in northwest Syria.

It is commonly used as a hair dye. The material can also reduce dandruff, kill ringworm and head lice, act as a sunscreen. As it produces a cooling effect, in India, especially in desert areas where the temperatures are extremely high, henna was cool the body.

Staining properties of henna are due to the presence of the compound 2-hydroxy-1,4-naphthoquinone, also known as lawsone, hennotannic acid, or natural orange 6. It is present in the leaves. The leaves are plucked and dried and ground into a paste.

English: Mehndi or Henna Lawsonia inermis in H...
English: Mehndi or Henna Lawsonia inermis in Hyderabad , India. (Photo credit: Wikipedia)

Henna paste is prepared by mixing crushed dry henna leaves with a mild acidic ingredient like juice of lemon which helps in releasing the dye from the petals. Different oils and herbs may also be added to enhance the scent of the paste.

At room temperature, it normally takes about a day for the acid to activate the dye and three days for the paste to lose its staining capabilities. The process is faster in hotter environments.

Lawsone dye infuses skin, hair, and porous surfaces but does not permanently or chemically alter them. The dye molecules, which are about the same size as amino acid molecules, migrate from the henna paste into the outermost layer of the skin. After the dried paste is scraped off the skin, air oxidation or perspiration can further darken the stain over the next 48 hours.