The Hidden 'Blue Gold' - Indigo

Indigo dye is an organic compound with a distinctive blue color. At once evidenc of blue found in primitive caves had proved that you can find a indigo color soil around few parts of India around 9000-8000 years age,but now it is extinct.Today,  Indigo is a natural dye extracted from the leaves of some plants of the Indigofera genus, in particular Indigofera tinctoria. Dye-bearing Indigofera plants were commonly grown and used throughout the world, particularly in Asia, with the production of indigo dyestuff economically important due to the historical rarity of other blue dyestuffs.

History 

word indigo is derived from Greek, meaning from India. Indigo cultivation is thought to have existed in the Indus Valley (present-day Pakistan and northwest India) more than 5,000 years ago. There, the color was called nila meaning “dark blue” and, as good things often do, it spread.By the time European traders arrived in Goa in the early 1500s, Indian indigo was one of the goods they took home.

The color was so prized that indigo was considered “blue gold.” It became one of the most profitable commodities for the two largest shipping conglomerates of the day: British East India Company and Dutch East India Company.

In 1865 the German chemist Adolf von Baeyer began working on the synthesis of indigo. The synthesis of glycine from the easy to obtain aniline provided a new and economically attractive route. BASF developed a commercially feasible manufacturing process that was in use by 1897, at which time 19,000 tons of indigo were being produced from plant sources. This had dropped to 1,000 tons by 1914 and continued to contract. By 2011, 50,000 tons of synthetic indigo were being produced worldwide.

Techniques 

Natural indigo is obtained from a variety of plants, the most widely used one being indigofera tinctoria. This shrub grows wild and is cultivated in tropical areas throughout the world. Indigo powder - the famous blue dye - is extracted from the leaves of the indigo plant. The extract may be purchased as lumps or chips (both of which require grinding before use) or as a fine powder. 

Two different methods for the direct application of indigo were developed in England in the 18th century and remained in use well into the 19th century. The first method, known as 'pencil blue' because it was most often applied by pencil or brush, could be used to achieve dark hues. Arsenic trisulfide and a thickener were added to the indigo vat. The arsenic compound delayed the oxidation of the indigo long enough to paint the dye onto fabrics. 

The second method was known as 'China blue' due to its resemblance to Chinese blue-and-white porcelain. Instead of using an indigo solution directly, the process involved printing the insoluble form of indigo onto the fabric. The indigo was then reduced in a sequence of baths of iron sulfate, with air oxidation between each immersion. The China blue process could make sharp designs, but it could not produce the dark hues possible with the pencil blue method.

Around 1880, the 'glucose process' was developed. It finally enabled the direct printing of indigo onto fabric and could produce inexpensive dark indigo prints unattainable with the China blue method.

Environmental Impact and Sustainable Solutions of modern dying 

The process of dyeing textiles with indigo is extremely resource-intensive, polluting and harmful to workers, particularly when done on an industrial scale. Modern indigo dyes are derived from crude-oil, which have an environmental and geopolitical cost. According to the World Bank, 17-20% of industrial water pollution comes from textile dyeing and treatment. Seventy-two toxic chemicals in our water come solely from textile dyeing, of which 30 cannot be removed.

In the 1970s and 1980s the jeans capital of the world was located in El Paso, Texas. By the mid-1990s El Paso’s jeans industry was in steep decline—a pair of jeans could be made in Xintang, China for a quarter of the price and in a place with few pollution controls. A pair of jeans can consume over 3,700 liters (975 gallons) of water and produce over 33kg of carbon.5 The water in the area is so polluted, smelly and black that homes are worthless. It is the source of drinking water for several million people, but the water is not drinkable and is carcinogenic to humans. This same issue is also happening in densely populated Bangladesh where pollution is increasing because of the political and economic power of the textile industry.

Ways we Can Help

As individuals, there are ways we can contribute to a more sustainable indigo industry. Supporting brands that prioritize natural indigo dyes and sustainable practices helps create demand for responsible production. Additionally, learning about indigo’s history, raising awareness, using plant-based indigo for own creations, can lead to a deeper understanding of the social and environmental implications of our consumption choices.