INDIGO

In this culturally diverse world, it is difficult to find anything that is equally embraced all across the globe. One such thing that has made to this list and found place in wardrobes all around the world, transgressing the local culture is the Jeans!

The Indigo dye used for blue Jeans, today, is a billion dollar industry, with its history dating back to 55 BC. The Britons used this wonder dye, which was made of woad. Blue was a symbol of valour and courage. A document written after the invasion of Britain by Julius Caesar records the love they had for blue. They believed that the occasional bluish colour gave a more terrible appearance during the fight!

In ancient India, the Indigo industry was thriving and was the led producer in the world. The etymology of the word INDIGO can be traced back to the Greek work INDIKON meaning Indian.

Indigo is a tetracyclic organic compound. It has alternate double bonds which give rise to the typical blue colour in the range of 450-420nm. This dye is found naturally in the leaves of woad or Isatis tinctorial found in Asia and Africa. The leaves are fermented in vat, in the presence of strong alkali such as potash. This when hydrolysed yields a colourless water soluble form of the dye, known as the leuco dye. The fabric to be dyed is immersed in it and on exposure to air, the leuco dye undergoes oxidation to form Indigo, which is water insoluble blue pigment, firmly attached to the fibres.

Isatin

Thanks to the presence of few colouring compounds present along with the natural Indian dye and its uneven colouring and the huge market worldwide, there began a search for effective ways to artificially synthesise Indigo.

Adolf von Baeyer, for the very first time, in 1870, synthesised Indigo using isatin as the starting material and published the same in1883. In 1890, BASF & Hoechst found an economic way for large scale production of Indigo using naphthalene as the starting material. Four years later, Hoechst also reported a method for synthesising Indigo from aniline. This was a huge blow to the Indian Indigo Industry. By the start of 20^th century, the global demand shooted up while that for natural Indigo crashed. During I world war, the trade between Germany and Britain virtually came to a standstill, creating a market for Indian Indigo in Britain. Though this was a significant revival, it failed to compete in the global market. Aniline, which is toxic, is locked into the fabric and can’t be washed off. Arachroma, a Swiss firm found an aniline free process of synthesis of Indigo for denims.

There is a rich chemical, cultural and political history weaved between each and every strand of denim. So, the next time you flaunt a pair of Jeans, do remember the pigmented past of the the brave blue!

INDIGO