Science Writing · Chemistry · History

The Blue That Brought Gandhi to Bihar

Gandhi's first satyagraha in India was fought over a dye. A chemist's look at indigo, the vats of Champaran and a German laboratory that made things worse for the ryots.

On Gandhi Jayanti we mostly talk about salt, the charkha and the marches. I want to talk about a dye. Gandhi's first satyagraha in India was fought over indigo, and it was fought here in Bihar. On 15 April 1917 he got off the train at Motihari, in Champaran district, to find out why the indigo cultivators there were so desperate.

By his own account in the autobiography, he had not even heard of Champaran before then, and did not know where it was. He had seen packets of indigo but had hardly any idea how the stuff was grown. As a chemistry teacher in Bihar, I think the chemistry side of this story deserves more attention than it usually gets.

Three kathas out of twenty

Much of the land in Champaran belonged to big estates, which leased it out to European planters. The tenants farming it were tied to what was called the tinkathia system. For every 20 kathas they held (about a bigha), 3 kathas had to go under indigo, and the crop was sold to the planter at whatever price he set.

Indigo was given the best plots and wore the soil out. The price the planter paid seldom covered what it cost to grow. Ryots who refused could expect fines, beatings and a long list of illegal cesses. Very little of the money made from Champaran indigo stayed with the people who grew it.

Where the blue comes from

Pick a leaf of Indigofera tinctoria and it is plain green. There is no blue in it at all. What the leaf holds is indican, a colourless compound made of indoxyl with a glucose unit attached. The plant stores it this way because the sugar keeps it soluble and stops it reacting.

In the kothis, the indigo factories scattered across Champaran, the cut plants were steeped in brick vats of water. Over the next several hours, enzymes in the leaves (helped by bacteria in the water) split off the glucose, and free indoxyl collected in a yellowish liquid.

Next, the liquid was let into a second vat and labourers beat it with paddles for hours. All that beating was there to get air into it. Oxygen joins two indoxyl molecules together into one molecule of indigo:

Indigo will not dissolve in water, so it came out as a blue sludge at the bottom of the vat. The sludge was boiled, strained, pressed and cut into dark cakes for sale abroad. So the peasant handed over a green crop, and what the planter sold had gone through a fermentation and an oxidation in between.

How indigo dyes cloth

Because indigo doesn't dissolve, it doesn't wash out either, which is why it makes such a good dye. It also creates a problem: something insoluble can't soak into cotton. Dyers got around this with redox chemistry, centuries before anyone used that word.

In an alkaline vat the indigo is reduced to leuco-indigo, sometimes called white indigo. This form is pale yellow-green and it dissolves. Cloth goes into the vat and takes it up. Once the cloth is pulled out, air oxidises the leuco-indigo back to blue indigo, now locked inside the fibres. If you have ever seen cloth come out of an indigo vat greenish and turn blue within a minute, you were watching that oxidation. Dyes applied this way are called vat dyes.

As for why it is blue, the indigo molecule is flat, with alternating single and double bonds that let its electrons spread over the whole structure, and hydrogen bonds inside the molecule keep it rigid. So it absorbs orange-red light strongly. The light that reaches our eyes is what's left, and we see it as a deep blue.

Competition from Germany

In Germany, meanwhile, Adolf von Baeyer had been working on indigo for years. He first made it in the lab in 1878, found better routes around 1880 and pinned down its structure in 1883. This work was part of the reason he received the Nobel Prize in Chemistry in 1905. The firm BASF then spent heavily on a route that would work at factory scale, and in 1897 it put synthetic indigo on the market. It was purer and more uniform than the plant product, and before long it was cheaper as well.

Natural indigo never recovered. World production fell from about 19,000 tonnes in 1897 to under 1,000 tonnes by 1917. In Champaran the planters' profits shrank, and they made the ryots pay for it. Some agreed to free tenants from growing indigo, but only in return for a large lump sum, called tawan. Others put up the rent on the freed land, a rise known as sharahbeshi. When German dyes were cut off during the First World War, demand for natural indigo picked up for a while and the old pressure to grow it came back.

The Champaran ryot ended up paying for the old system and for a discovery made in a German laboratory, both at once.

Gandhi's inquiry

The man who brought Gandhi to Champaran was Raj Kumar Shukla, a cultivator from the district. He had followed Gandhi around at the Lucknow Congress in December 1916 and would not let the matter drop. Soon after Gandhi reached Motihari, the district magistrate ordered him out. Gandhi refused, said he would accept whatever penalty followed, and the government withdrew the case.

For me, as a scientist, the most interesting part is what came next. Gandhi and a group of Bihar lawyers, Rajendra Prasad among them, went through the villages and took down statements from more than 8,000 peasants. Each one was recorded and questioned closely. By the end there was far too much evidence to wave away.

In June 1917 the government set up an inquiry committee and made Gandhi a member. It submitted a unanimous report on 3 October 1917. The Champaran Agrarian Act followed in 1918, abolishing tinkathia and requiring planters to return a quarter of the tawan they had collected. Within about ten years most of the planters had left the district.

Looking back

Champaran is usually remembered as a political event, which of course it was. But chemistry runs all through it: the indican in the leaf, the fermentation in the vat, the oxidation that labourers drove with their paddles, and a synthesis in Germany that undercut a whole district's economy.

Science did nothing to free the ryots. For some years synthetic indigo actually made their position worse. They were freed by careful fact-finding and by people who refused to put up with what was being done to them. I think that is worth telling our students on Gandhi Jayanti, along with the chemistry.

Almost all the indigo in blue jeans today is synthetic. Chemically, it is the same molecule that brought Gandhi to Bihar.