INDIGO

Sources

A variety of plants have provided indigo throughout history, but most natural indigo is obtained from those in the genus Indigofera, which are native to the tropics. In temperate climates indigo can also be obtained from woad (Isatis tinctoria) and dyer's knotweed (Polygonum tinctorum).

The primary commercial indigo species in Asia was true indigo (Indigofera tinctoria, also known as Indigofera sumatrana). In Central and South America the two species Indigofera suffruticosa (Anil) and Indigofera arrecta (Natal indigo) were the most important.

The plants of the genus Indigofera produce a much stronger dye that those of the Isatis (woad) family; however, dyer’s woad is much more easily cultivated and therefore more widely used than Indigofera, which needs a tropical climate. Isatis tinctoria grows up to approximately 1.50 m(5’) in height and can be harvested three times a year.

 

1) INDIGOFERA TINCTORIA


Indigofera tinctoria
 


Preparation of indigo dye with Indigofera tinctoria

After the field has been ploughed, the seeds are planted at the beginning of the rainy season and are ready to harvest in 4 months. Indigo plant is suitable to grow in areas not subject to flooding, for example, in the back yard of the house or the area around the shelter where cows and buffaloes are kept. The high land near the rice paddy is also suitable for growing this indigo plant. Little care is needed for young plants. All that is needed is to keep weeds away from the young plants until they grow 1 foot high, and then keep the cows and buffaloes from destroying the indigo plant before harvesting.
 

Four months after planting the seeds the leaves of the indigo plant start turning dark green which indicates good quality dye. The plants are cut off and made into small bundles.

The leaves are then soaked in a large earthenware jar filled with water and left to be fermented in order to convert the glycoside indican which is naturally present in the plant to the blue dye indigotin. The precipitate from the fermented leaf solution is mixed with a strong base such as lye, pressed into cakes, dried, and powdered. The powder is then mixed with various other substances to produce different shades of blue and purple.

 

Indigofera tinctoria in history

The name indigo comes from the Roman term indicum, which means a product of India. This is somewhat of a misnomer since the plant is grown in many areas of the world, including Asia, Java, Japan, and Central America. Another ancient term for the dye is nil from which the Arabic term for blue, al-nil, is derived. The English word aniline comes from the same source.

The color indigo, often associated with political power or religious ritual, has held a significant place in many world civilizations such as Mesopotamia, Egypt, Greece, Rome, Mesoamerica, Iran, and Africa for thousands of years. In the excavation of Thebes an indigo garment dating from c. 2500 B.C. was found, for example — furthermore, the Hindu god Krishna is most often depicted in blue, human sacrifices were often painted blue in ancient Mayan culture, and the Virgin Mary is regularly imagined draped in blue clothes in Christian art.

In Mesopotamia, a Neo-Babylonian cuneiform tablet of the 7th century BC gives a recipe for the dyeing of wool, where lapis-colored wool (uqnatu) is produced by repeated immersion and airing of the cloth.

The dye is first mentioned in a written source for Western Europe in the histories of Herodotus (writing around 450 B.C.), who described its use in the Mediterranean area. The Romans used indigo as a pigment for painting and for medicinal and cosmetic purposes. It was a luxury item imported to the Mediterranean from India by Arab merchants. Indigo plant used to be planted in Khuzestan and other southern regions of Iran too. It was at the time of the Crusades, however, that indigo became one of the valued “spices” that Italian merchants acquired in Cyprus, Alexandria and Baghdad. These cities were themselves end-points for caravans from the Far East. But the trade in indigo dye only became a commercial force after 1498 with the opening of the sea route to India. This is not to say that Europeans had no other way of obtaining deep blue dye. The woad plant, native to northern Italy, southern France, and parts of England and Germany, yielded indigo-colored dye from its leaves, but it was inferior to that obtained from the indigo plant. Quite naturally, the woad-growers of Europe (both peasants and princes) sought to protect their industry against the influx of affordable indigo in the 16th century. In 1598 indigo was prohibited in France and parts of Germany, and dyers had to swear, often on the pain of death, that they would not use that dye. Nevertheless, in the 17th century indigo became one of the chief articles of trade of both the Dutch and the British East India Companies. Dauril Alden argues that, in fact, the indigo supplies in India were not sufficient to meet the European demand in the 17th century and that is why indigo cultivation was taken up in the New World as well.

In Japan, indigo became especially important in the Edo period (The Edo period (江戸時代 Edo-jidai), also called Tokugawa period, is a division of Japanese history running from 1603 to 1868) when it was forbidden to use silk, so the Japanese began to import and plant cotton. It was difficult to dye the cotton fiber except with indigo. Many years later the use of indigo is very much appreciated as a color for the summer Kimono Yukata, as the blue sea and the nature are recalled on this traditional clothing.
 

An indigenous variety of indigo began to be cultivated by Spanish overseers on the plantations of Honduras and the Pacific slopes of Central America in the 1560s. The indigo plant was known to early Guatemalan colonialists by the Nahuatl word xiquilite, and the dye was known to contemporaries as “Guatemalan Indigo.” M. De Beauvais Raseau, writing about indigo cultivation in the Eighteenth Century, stated that the Native Americans also knew about extracting dye from the plant. They called it “Tlauhoylimihuitl” and used it to darken their hair. It seems that indigo production continued to increase throughout the 17th century in the New World. The French colony of Saint Domingo eventually became the major producer of indigo, and this dye was also of the best quality. The English gained their first indigo-producing colony in this part of the world in 1655 when they captured Jamaica. However, it is unclear how important New World indigo was in the worldwide indigo market, as prices fluctuated and so did production numbers. By 1740 sugar had replaced indigo as the main crop of Jamaica, but, on the other hand, this was also the beginning of the indigo boom in South Carolina.

It seems that “Guatemalan indigo” did not enjoy as high a reputation in Europe as indigo from Asian countries. In 1746, when “A Friend to Carolina” wrote his tract encouraging the cultivation of indigo in South Carolina he emphasized the necessity of establishing a superior product: “All Kinds [of indigo dyes] are better or worse, as they are neat or pure; for those who make it in America, often maliciously mix it with Sand and Dirt, but the Cheat is easily discovered; as Indigo that is fine and pure will burn like Wax, and, when burnt, the Earth or Sand will remain.” He pointed out that in the Americas indigo dye was often made with the stems and branches of the plant instead of just with the leaves. He felt that this too might be detrimental to its quality — “But one ought to have the Leisure and Patience of the Indians, to undertake such a Work [stripping the leaves], and have Workmen as cheap as they are in that Country.”
 
 
Beauvais-Raseau, L’Art de l’Indigotier. Paris: L.F. Delatour, 1770.
 
 

Raseau, who was captain of the militia on Saint Domingo prior to 1770, discusses the history of indigo in all the regions of the world where it could be grown. He gives various methods that were employed for extracting the dye and then goes into greater detail on indigo production in South and Central America. His wonderful little book contains diagrams of the plants, the process of making indigo dye, as well as the ideal plantation. Indigo plantations did not require much labor except during July, August and September when the plants were cut, fermented and the dye was extracted. Because it was thought that the Indians were particularly susceptible to the diseases that bred around the fermentation vats, plantation owners claimed that they did most of the field work, while Black slaves extracted the dye. In reality, the division of labor was probably not so strict — particularly since Black slaves were in relatively short supply and were often more expensive to hire than the Indians.


John Stedman in his "Narrative of five years" expedition described the extraction of the dye throughly. Stedman was invited to view the process of making indigo dye at the plantation of the governor of Surinam and he gives the following account of it:

"When all of the verdure is cut off, the whole crop is tied in bunches, and put into a very large tub with water, covered over with very heavy logs of wood by way of pressers: thus kept, it begins to ferment; in less than 18 hours the water seems to boil, and becomes of a violet or garter blue colour, extracting all the grain or colouring matter from the plant; in this situation the liquor is drawn off into another tub, which is something less, when the remaining trash is carefully picked up and thrown away; and the very noxious smell of this refuse it is that occasions the peculiar unhealthiness which is always incident to this business. Being now in the second tub, the mash is agitated by paddles adapted for the purpose, till by a skillful maceration all the grain separates from the water, the first sinking like mud to the bottom, while the latter appears clear and transparent on the surface: this water, being carefully removed till near the coloured mass, the remaining liquor is drawn off into a third tub, to let what indigo it may contain also settle in the bottom; after which, the last drops of water here being also removed, the sediment or indigo is put into proper vessels to dry, where being divested of its last remaining moisture, and formed into small, round, and oblong square pieces, it is become a beautiful dark blue, and fit for exportation. The best indigo ought to be light, hard, and sparkling."

These blocks of indigo were what was so highly prized on the European market.

Demand for indigo dramatically increased during the industrial revolution, in part due to the popularity of Levi Strauss's blue denim jeans. The natural extraction process was expensive and could not produce the mass quantities required for the burgeoning garment industry. In 1865 the German chemist Johann Friedrich Wilhelm Adolf von Baeyer began working with indigo. His work culminated in the first synthesis of indigo in 1880 from o-nitrobenzaldehyde and acetone upon addition of dilute sodium hydroxide, barium hydroxide, or ammonia and the announcement of its chemical structure three years later. BASF developed a commercially feasible manufacturing process that was in use by 1897. In 1905 Baeyer was awarded the Nobel Prize for his discovery.

Recipe of dyeing wool with indigo

Indigo with Urine The proportion needed is double the weight in grammes of powdered indigo to litres of urine. Indigo is stirred little by little into urine fermented for ten to fourteen days outside at a temperature of at least 24°C (75°F) in a sealed container. After another ten to fourteen days outside in the sun, with daily stirring, the indigo should have dissolved and the liquid can be used for dyeing. One generous quarter litre of the liquid added to 25 litres (5 ½ gallons) of water will dye one kilo of wool.

 

 

2) DYER'S WOAD (ISATIS TINCTORIA)

 

 

Dyer's woad (or glastum) is the common name of the flowering plant Isatis tinctoria in the family Brassicaceae. It is occasionally known as Asp of Jerusalem. Woad is also the name of a blue dye produced from the plant.

Woad is native to the steppe and desert zones of Azerbaijan, Central Asia to eastern Siberia and Western Asia (Hegi), but is now found in southeastern and some parts of Central Europe as well. It has been cultivated throughout Europe, especially in Western and southern Europe since ancient times.
Kingdom: Plantae
Division: Magnoliophyta
Class: Magnoliopsida
Order: Brassicales
Family: Brassicaceae
Genus: Isatis
Species: I. tinctoria

History of woad cultivation

Dyer's woad (besided henna - Lawsonia inermis L., Lythraceae) is known to be used as a hair dye in medieval Azerbaijan.

Until the end of the 16th century, when indigo became available as trade routes from the far east developed, woad was the only source for blue dye available in Europe.

The first archaeological finds of woad seeds date to the Neolithic and have been found in the French cave of l'Audoste, Bouches du Rhone (France). In the Iron Age settlement of the Heuneburg, Germany, impressions of the seeds have been found on pottery. The Hallstatt burials of Hochdorf and Hohmichele contained textiles dyed with woad.

Julius Caesar tells us (in de Bello Gallico) that the Britanni used to mark their bodies with vitrum; this has often been assumed to mean that they painted or tattooed themselves with woad. However vitrum does not translate to "woad", but probably more likely refers to a type of blue-green glass which was common at the time. The Picts may have gotten their name (Latin Picti which means painted folk or possibly tattooed folk) from their practice of going into battle naked except for body paint or tattoos. (This has been commemorated in the humorous (modern) British song The Woad Ode.) However, more recent research has cast serious doubt on the assumption that woad was the material the Picts used for body decoration. Contemporary experiments with woad have proven that it does not work well at all as either a body paint or tattoo pigment. Highly astringent, when used for tattooing or placed in wounds woad produces quite a bit of scar tissue and, once healed, no blue is left behind. The common use of dung as an ingredient in traditional woad dye preparations also make it unlikely to have been suitable for application to wounds.

In Viking age levels at York, a dye shop with remains of both woad and madder dating from the 10th century have been excavated. In Medieval times, centres of woad–cultivation lay in Lincolnshire and Somerset in England, Gascogne, Normandy, the Somme, Toulouse and Britanny in France, Jülich, the Erfurt area in Thuringia in Germany and Piedmont and Tuscany in Italy. The citizens of the five Thuringian woad-towns of Erfurt, Gotha, Tennstedt, Arnstadt and Langensalza had their own charters. In Erfurt, the woad-traders gave the funds to found the University of Erfurt. Traditional fabric is still printed with woad in Thuringia, Saxony and Lusatia today: it is known as Blaudruck (literally, 'blue dyeing').

Medieval uses of the dye were not limited to textiles. For example, the illustrator of the Lindisfarne Gospels used a woad-based pigment for blue paint.

Recently, scientists have discovered woad might be used to prevent cancer, having more than 20 times the amount of glucobrassicin contained in broccoli. Young leaves when damaged can produce more glucobrassicin, up to 65 times as much.

In Germany, there are attempts to use woad to protect wood against decay without dangerous chemicals. Production is also increasing again in the UK for use in inks, particularly for inkjet printers, and dyes, as woad is biodegradable and safe in the environment, unlike many synthetic inks. Isatis tinctoria is viewed as an invasive species in parts of the United States.