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Denim owes its iconic blue hue to indigo, the remarkable dye that has shaped its identity. Once referred to as “blue gold,” indigo has historically symbolized power and prosperity, often reserved for royal and ceremonial attire. Extracted from the fermented leaves of the Indigofera plant, this pigment has traversed through millennia and across continents, coloring textiles and enriching stories and civilizations. Today, every pair of jeans embodies a rich cultural heritage, woven from artisanal traditions, influenced by global trade routes, and shaped by industrial revolutions—a fascinating journey that begins with a plant and ends at the heart of our wardrobes.
Where is indigo obtained from?
The Swedish botanist Carl Linnaeus officially named the Indigofera genus in his 1753 work, “Species Plantarum.” However, many civilizations worldwide had already been using indigo for thousands of years to dye textiles and create artworks. The oldest indigo-dyed textile, which dates back over 6,000 years, was discovered in Huaca Prieta, Peru, one of South America’s earliest known human settlements.
Indigo dye is produced by fermenting the leaves of the Indigofera plant, resulting in a yellowish liquid that turns a deep violet-blue when oxidized in open vats. After oxidation, the water is evaporated to collect the sediment that settles at the bottom, which is then sold as solid indigo.
Plants in the Indigofera genus belong to the legume family and include over 750 species. They can grow taller than 1.80 meters and are characterized by oval leaves shaped like feathers. Indigofera thrives in tropical climates; in the Indian subcontinent, Indigofera tinctoria—commonly referred to as “true indigo”—is especially prevalent, while Indigofera suffruticosa is predominantly found in Central and South America.
The use of indigo in ancient civilizations
Indigo is not native to Europe but has been known in the Mediterranean for millennia. Indigo-dyed bands have been discovered in Egyptian textiles from the Fifth Dynasty, around 4400 BCE. Its use was also documented by both Greek and Roman civilizations, who obtained the pigment through Arab traders. Pliny the Elder notably described indigo as a product of India (the Latin word “indicum” means “from India”). Still, its use remained rare due to high costs and the difficulty of importation.
Many scholars believe that the people of the Middle East were among the first to recognize and utilize the properties of the Indigofera plant. Its cultivation likely spread from the Indus Valley, now part of Pakistan and northeast India. Records indicate that indigo was used in China around 3000 BCE, and Marco Polo described its use in India during the 13th century.
In the Andean region, the Inca used indigo to dye textiles, bodies, and pottery. The Maya created their signature “Maya Blue” by mixing fermented Indigofera leaves with clay to decorate sculptures, walls, and ceramics. The Aztecs dyed luxurious fabrics, including the emperor’s cloak, with indigo and used Indigofera as a medicinal plant to treat various illnesses.
Indigo during the colonial period
In later centuries, the cultivation of indigo was influenced mainly by European colonial interests. As previously noted, Indigofera had been grown in the Americas for thousands of years before the arrival of the Spanish. They recognized the large-scale production of indigo as a significant opportunity to compete with the Portuguese, who had begun importing indigo from Goa to Europe in the early 16th century.
Consequently, Europe started importing indigo from modern-day Guatemala in the 16th century. By the 18th century, Venezuela and Mexico had also developed extensive Indigofera plantations. Around the same period, the French and British introduced indigo cultivation to the Caribbean, particularly in Haiti and Jamaica. The traditional knowledge of enslaved Indigenous peoples and Africans was crucial in making these plantations highly profitable for European colonists.
The importance of indigo in Europe
In 1498, the Portuguese explorer Vasco da Gama discovered a new sea route between India and Europe, making it easier to import indigo without relying on Arab intermediaries. Prior to this, Europe primarily used a native plant called woad to produce blue dye. As a result, the introduction of indigo across the continent was slow, and resistance was faced. Between the 16th and 17th centuries, woad producers even referred to indigo as “the devil’s dye” and threatened death to anyone who used it.
English dyers were hesitant to replace woad with indigo, despite the latter’s superior dyeing properties for cotton and flax. In France, indigo was banned to protect the domestic woad industry; however, the aristocracy’s obsession with the color blue led many to ignore the ban, which was ultimately lifted in 1737. Consequently, France gained a monopoly over indigo, which was even used for Napoleon’s extensive military uniforms.
From Genoese fustian to contemporary denim
In contrast, Italy emerged as one of the leading European hubs for Eastern imports as early as the 16th century, including indigo. Genoa, in particular, was one of the most important ports in the world at that time. This combination of factors allowed Genoese fustian to stand out among its European competitors. Unlike other affordable and durable fabrics, Genoese fustian was made with a cotton weft and indigo-dyed warp, making it the actual ancestor of contemporary denim. Sailors and dockworkers wore it for its strength and practicality.
From U.S. independence to India’s
In the 18th century, indigo cultivation made its way to the southern United States, especially in South Carolina, largely due to a temporary decline in the colony’s main crop: rice. Indigo quickly became more profitable than cotton and sugar. Between the second decade of the century and its end, indigo exports from the U.S. to Europe increased sixfold. The pigment was so valuable that it was even used as a currency during the American Revolution.
After the British withdrew from the U.S. following the war, they turned back to India as a source of raw materials and cheap labor. There, too, the traditional knowledge of indigo cultivation was exploited for colonial profit. Indigo became one of the most lucrative goods for the two major commercial empires of the era: the British East India Company and the Dutch East India Company.
In 1859, Bengali farmers revolted against British exploitation in the Indigo Revolt, which consisted of a coordinated series of mostly nonviolent protests and petitions that aimed for better working conditions on local plantations. This rebellion was one of the early events that ultimately contributed to India’s independence nearly a century later and the end of British colonial rule.
What is synthetic indigo?
The process of extracting indigo from Indigofera leaves may seem straightforward, but it is actually complex and labor-intensive. This complexity makes the invention of synthetic indigo a true revolution. In the late 19th century, German chemist Adolf von Baeyer first synthesized indigo and won the Nobel Prize in Chemistry in 1905 for his work. Synthetic indigo made this dye even more accessible, leading to a significant decline in Indigofera plantations around the world.
Today, the denim industry utilizes both traditional powdered indigo and pre-reduced indigo, which is treated to become water-soluble. All forms of indigo are poorly soluble in water and require additional substances to bond with the fibers. However, pre-reduced indigo is preferred for environmental reasons, as it reduces the usage of sodium hydroxide by 52% and sodium dithionite by 63% compared to powdered indigo, which is still popular due to its lower cost.
Returning to natural indigo
In recent years, there has been a growing interest in returning to natural indigo, both for its environmental benefits and for the vibrant, authentic blues that synthetic dyes cannot replicate. Indigofera plants have the ability to sequester carbon in the soil and fix nitrogen in the atmosphere, enhancing soil quality and helping to mitigate climate change. This makes Indigofera especially suitable for regenerative agriculture.
