Indigo has enchanted humans with its dazzling range of blues for over 6,000 years. When we pull on a pair of blue jeans, we clothe ourselves in thousands of years of drama. Imagine how magical it must have felt when our prehistoric ancestors first witnessed a pile of fallen indigofera leaves in a pool of urine turn from clear yellow to emerald green to teal and finally to dark indigo blue. Little did I know how deep the history is when I first fell in love with indigo. Denim and fast-fashion’s modern-day ubiquity makes it easy for us to ignore the fact that blue dyes have been laboriously extracted for millenia at great human, financial and ecological cost.
In this post, I share some of the fascinating and fraught history I’ve learned about indigo: from ancient indigo and colonial indigo plantations’ slavery and worker rebellions, to the current day synthetic indigo made out of crude oil, the source of over 99% of the denim blue we wear today. I also explore possibilities for us to make our future use of indigo more ethical and sustainable.
Ancient indigo
Indigo dyes have been used by our human ancestors for many millennia, using dye-containing plants of the Indigofera genus, native to tropical Asia, Africa and Americas, as well as the Isatis genus native to the Mediterranean. The oldest known evidence of indigo dye using Indigofera plants is a 6,200 year-old piece of indigo-dyed cotton found at the Huaca Prieta ceremonial mound in northern Peru. The next oldest known indigo dyed cloth is a roughly 4,400 year-old textile from Egypt. The striped linen cloth wrapped around Egyptian mummies as well as the ceremonial robes of King Tut were likely dyed blue using indigo from the Isatis tinctoria (woad) plant. The oldest known cultivation of Indigofera plants was during the Bronze Age Indus Valley Civilization (3300 -1300 BC) in present-day India and Pakistan. India has been such an important source for the dye that the Greeks called the blue dye indikón, for “product from India,” which became indigo in English. The earliest evidence of indigo dyeing in China (藍染, lán rǎn), the type I’m most familiar with, was found in Wuyi Mountain and is a relative baby at 3,400 years old.
While red and yellow are primary textile colors easily extracted from readily available plants and insects around the world, blue is one of the most difficult textile colors to produce from nature. A mysterious, tiny 2-inch 600 BC neo-Babylonian cuneiform tablet was unearthed in the 1880s, and it wasn’t until the 1990s that scholars deciphered the text: instructions for indigo dyeing. The process for dyeing wool blue was important enough to ancient Mesopotamians that someone recorded it on a clay tablet. Altogether, these archaeological findings suggest that people discovered the indigo dyeing process independently at different times all over the world, using native plant species containing indigo.
Colonial indigo plantations
Prior to the development of synthetic indigo in 1897, the only known sources for color-fast blues were indigo-containing plants and murex snails. The Indigofera tinctoria plant, whose leaves have the highest concentration of indigo, only contain 0.2-0.8% indican, the precursor to indigo dye. A 2,000 square foot field of Indigofera tinctoria plants will produce a mere half-pound of indigo dye in an arduous, multi-day process requiring multiple workers harvesting, fermenting, beating, draining and heating into dye cakes.
Given how much toil goes into growing, harvesting, processing and transporting indigo from tropical farmlands, it became an expensive, fetishized commodity. Indigo dye was a luxury product for Indian elites, wealthy West Africans and Tuareg nomads in the Sahara, European royals, and Japanese aristocrats. Even ancient Mesopotamians, Greeks and Romans Imported indigo from India via Arab merchants, who appreciated the portability of the expensive yet compact blue dye cakes. In West Africa, indigo was used as a currency during the slave trade. Indigo thus earned its nickname of “blue gold.”
Indigo mass production and trade blew up in the 1700-1800s with the expansion of European colonization. Indigo plantations were established in the Caribbean and the Americas, which exploited the expertise and skill that enslaved people from West Africa brought with them around indigo cultivation. In the 1700s, US profits from indigo exceeded profits from sugar and cotton. People and land in colonized tropical regions around the world were forced to produce indigo for wealthy Europeans. My Hakka family homelands in Taiwan farmed indigo not only for their own traditional clothing but also for their Qing dynasty and Japanese colonizers. In 1859, Bengali peasant indigo farmers and workers rose up against exploitative European planters in a movement called the Indigo Revolt, which led to an Indigo Commission and reformation of such practices as forcing farmers to grow indigo over essential food crops, meager compensation, and destruction of farmers’ property when they disobeyed these unethical and authoritarian orders.
Current day synthetic indigo
It took 32 years for German chemist Adolf von Baeyer to develop synthetic indigo. He bought a chunk of indigo for his 13th birthday in 1848 and started experimenting with it until he and Viggo Drewson managed to synthesize indigo in their lab in 1880. Baeyer later won the Nobel Prize in Chemistry for his development of indigo and other dyes. By 1897, a commercially viable way of mass producing synthetic indigo from crude oil (!!) was developed by Karl Heumann (1897) and Johannes Pfleger (1901) with the financial backing of the German chemical company Badische Anilin- und Soda-Fabrik (BASF). BASF later played a major role in Nazi Germany and produced the notorious chemical Zyklon B used for mass murder during The Holocaust. (Zyklon B is derived from Prussian blue pigment – another nefarious use of color!) BASF continues to be one of the largest chemical producers in the world and a leading producer of synthetic indigo.
The launch of synthetic indigo production led to the collapse of indigo farming in the early 1900s. Today, over 99% of the indigo on the market is synthetic and derived from crude oil using additional fossil fuels in its processing. The market price of synthetic indigo is 10-20 times less than that of plant-based indigo, though the true ecological price of extracting fossil fuels is ultimately much greater. This reduction in market price led to cheaper indigo-dyed clothing, such as the peasant Mao jackets of Communist China and Levi’s workers’ jeans of the mid-1900s, all the way to the current fast fashion trend of denim-jean-like sweatpants.
Where does indigo from here?
The carbon footprint of fast fashion is now about 10% of global carbon emissions. Switching from fossil fuels back to renewable plant-based sources for textiles is one way to reduce our carbon footprint. Indeed, indigo farms are making a bit of a comeback in India to supply artisan textile makers. But if the total annual production of indigo dye was sourced from plants, it would require an estimated 2 million acres of cultivated land and produce large amounts of highly alkaline and dye-laden wastewater. Microbial indigo production processes using recombinant E. coli bacteria have been developed, but are still more expensive than synthetic indigo and have unclear environmental impacts.
To meaningfully reduce ecological harm, we must consume less. Using jeans as the model, this study estimates that viable alternatives to fast fashion include: traditional “slow fashion” (e.g. buying higher quality clothing that we wear over and over again over many years), buying second-hand clothing, renting clothing, and recycling clothing, all which reduce the clothing’s carbon footprint by 85% or more.
In my deep dive into indigo’s history, I uncovered a lot of dirty dealings and diabolical drama along with amazing ancestral ways we’ve learned to coax brilliant blues out of plants and onto our textiles and bodies. The huge ecological cost of our current consumption of indigo dyes and textiles in general is clearly not sustainable nor ethical. There are, however, many ways we can do better and make smarter choices by consuming less and choosing higher quality textiles made with renewable and recyclable materials.
As Robin Wall Kimmerer so eloquently writes in The Serviceberry: “What would it be like to consume with the full awareness that we are the recipients of earthly gifts, which we have not earned? To consume with humility? We are called to harvest honorably, with restraint, respect, reverence and reciprocity.”
I hope that we can all embrace and practice The Honorable Harvest principles. Our planet and all its dazzling colors depend on it.
Wow I learned so much!