Story of Indigo dye | The Blue Gold of India
Indigo, or indigotin, is a dyestuff extracted from the indigo and woad plants. Indigo was known all through the old world for its capacity to shade textures a dark blue. Indigo is an ancient dye and there is evidence for the use of indigo from the third millennium BC, and possibly much earlier for woad.
A frequently mentioned example is that of the blue stripes found in the borders of Egyptian linen mummy cloths from around 2400 BC.
Several sources claimed that ancient linen fabrics that are dyed blue are likely to have been dyed with indigo because indigo was thought to be superior to woad for dyeing linen. Another example was found on ancient tablets from Mesopotamia in 600 BC that explained a recipe for dyeing wool blue by repeatedly immersing and airing. The earliest example of indigo from Indigofera probably comes from the Harappan Civilization (3300 -1300 BC). Archaeologists also recovered remains of cloth dyed blue which dated back to 1750 BC from Mohenjo-Daro, now present day Sindh, Pakistan.
There are at least 50 different types of Indigofera in India. In the Northwest region, indigo has been processed into small cakes by producers for many centuries. It was exported through trade routes and reached Europe. Between 300 BC to 400 AD Greeks and Romans had small amounts of blue pigment in hard blocks, which they thought was of mineral origin. They considered it a luxury product and used it for paints, medicines and cosmetics.
Indigo was found to have high tinting strength although the colour faded rapidly when exposed to strong sunlight.
The Greeks called this blue pigment ‘indikon’, which translates into ‘a product from India’, this word then became Indigo in English. Another ancient term for the dye is ‘nili’ in Sanskrit which means dark blue from which the Arabic term for blue ‘al-nil’ was acquired. This word in Spanish was called anil and later made its way to Central and South America where it is simply referred to as indigo. The English word aniline is also derived from anil, and it is used to describe a class of synthetic dyes.
In the late 13th century Marco Polo returned from his voyages through Asia and described how indigo was not a mineral, but in fact was extracted from plants. Small quantities of indigo were available in Europe then, but they were very expensive due to the long journey required and the taxes imposed by traders along the route. Locally grown woad was the main blue dye used in Europe at the time. By the late 15th century Vasco da Gama discovered a sea route to China, allowing indigo to be imported directly. Large scale cultivation of indigo started in India and in the 1600s large quantities of indigo were exported to Europe. The cost of indigo dropped considerably and by the end of the 17th century it had virtually replaced woad in Europe.
Indigo was often referred to as Blue Gold as it the best possible trading commodity, although high value it was compact and long lasting.
The most widely recognised procedure of extracting Indigo colour is the point at which it is derived from the bushes of the Indigofera Tinctoria and Suffruticosa plants that have been particularly developed to make colours. The colour can be separated from either the leaves or the roots, however for reasons for sustainability, the colour from the leaves is utilised more often than not.
The leaves are then soaked in water so as to mature. This stage is one which basically removes the colour material from the plant, in spite of the fact that at this stage it is a lighter shade. After this point the leaves are removed and the existing solution is is then beaten and exposed in the air to form the Indican into Indigo Dye. Excess water is poured off and the blue slime is dried. This sludge is then pressed into balls and left to dry. This is the conventional indigo colour powder.
Typically, in the dyeing process, cotton and linen threads are usually soaked and dried 15-20 times.
After dying, the yarn may be sun dried to deepen the colour. The process of Indigo dyeing is completely different while done using the traditional process, it’s 100% natural and often organic. Instead of using heat and a mordant, it is done using a living fermentation process that naturally sets the dye into the textile. The texture colouring process takes no less than seven days, from colouring till drying. At first the texture is dunked in a vat of dye and kept under the water for a couple of minutes. When brought out into the air, the shading is a splendid green and gradually it changes to a wonderful profound and rich blue of Indigo.
The procedure is repeated around six to ten times, depending upon the shade required. It is then hung out to dry in the sun. By the end of the 19th century, natural indigo production was no longer able to meet the demands of the clothing industry and a search for a simpler and easier way to procure indigo started. In 1865, Adolf von Baeyer, a German chemist began working on the synthesis of indigo and in 1897 synthetic indigo was launched. The world’s current production of natural indigo could not cope with the demand for this dye. However, environmental concerns and an increased demand for natural and sustainable dyes may lead to a resurgence of natural indigo production. Although the chemical formula for natural as well as synthetic indigo is the same, synthetic indigo is almost pure indigotin.
Natural indigo has a high proportion of impurities such as indirubins, that give beautiful colour variations and the blue you get depends on where the indigo was grown and the weather at the time.
Synthetic indigo on the other hand, produces an even blue that never varies or fades with time. Natural indigo is a sustainable dye. After the pigment has been extracted the plant residue can be and id composted and used as a fertiliser whereas the water is reused to irrigate crops. The production of Indigo produces a variety of by-products that must be handled carefully.
Some of these materials are considered to be hazardous and must be disposed of in consideration with local and federal chemical waste disposal guidelines. Such chemicals can enter the environment in at least three different ways. The first, during the actual manufacture of the molecule. The second is when the dye is applied to the yarn, and the third is when the dye is removed from the yarn and enters the wash water during the initial stone washing or wet processing of the fabric.
This last step is typically undertaken to produce denim. Manufacturers who use indigo in dying operations are also seeking to improve their use of the dye.
Compared to traditional methods of stone washing fabric dyed with indigo, their new process uses few, if any, pumice stones which help give the fabric its faded look. Therefore, pumice stone handling and storage costs are reduced, along with time required to separate pumice from garments after stone washing. It also uses much less bleach. Therefore, this new process not only reduces garment damage, but also reduces waste produced by the stones and bleach.
Natural indigo can often be traced to its country of origin, and even to the farm where it was produced.
By using natural Indigo, we make a conscious effort will to help provide sustainable employment to rural population in third world countries. Not just that but you would also be contributing towards helping the environment and reducing the use of petrochemicals.