Tangled up in Blue: An Introduction to Indigo

If you’ve ever wondered where blue jeans got their color, or how natural dyers achieve deep, rich, dark blues, Leslie Ordal can answer these questions! Read on for the fascinating backstory of indigo. Originally published in knitscene Summer 2016.


Blue is one of the rarest colors to occur in nature, and as such, any substance that can confer the color to textiles and other items has always been highly valued. Synthetic dyes, usually cheaper and easier to use than natural dyes, were first developed in the 1850s and were subsequently adopted as the dyestuff of choice by most textiles manufacturers. Yet one of the oldest natural dyes—indigo—has retained a certain magic and mystery that, along with its extraordinarily complex blue color, have kept its dyeing traditions alive.

Indigo

From left to right: pots of indigo dye; working batik dye. All images courtesy of iStock.

Indigo is derived from any number of plants, most of which grow in the tropics, but also in the more temperate climes of Europe and eastern Asia. Plants in the genus Indigofera produce the greatest amount of indigo, but it’s also found in substantial quantities in plants such as woad, which has been cultivated in Europe as a dyestuff since at least 700 BCE. Indeed, indigo shows a remarkably long and varied history of use throughout the world. Fragments of indigo-dyed linen were found on the urns containing the Dead Sea Scrolls. Intricately patterned indigo-dyed cloth from Japan has been traced back to at least the seventh century CE, with the dye and its traditions likely brought over from China even earlier. Woad mills dotted the landscape of thirteenth-century Germany, providing indigo to textile producers in other parts of Europe. Plants of the Indigofera family flourished in the southeastern United States in the late eighteenth to early nineteenth centuries, a particularly dark chapter of the dye’s history wherein its demand and production supported the transatlantic slave trade.

Indigo-dyed textiles have been recovered from archeological sites around the world, with cultures from Japan, Southeast Asia, West Africa, Latin America, and Europe each creating their own methods and rituals for the production and use of blue textiles. Many cultures use indigo to make ikat textiles, where the yarn itself is dyed in sections that will create a particular pattern when woven—these have been especially important in Japan and other parts of Asia. Japan has a strong tradition of indigo dyeing that has dwindled to about a half-dozen families, but the knowledge continues to be passed on and maintained. Several groups of ethnic minorities in China are renowned for their unique use of indigo, such as the Dong peoples’ preference for heavily saturated and stiff indigo-dyed clothing, which is so dark and shiny it takes on a metallic, almost coppery appearance. This coppery look is also prized by the Touareg people of the Sahara, who use mallets to pound indigo pigment into already-dyed cloth. Indigo also retains a following in Mexico, especially in Chiapas and Oaxaca. Even with the arrival of both synthetically produced indigo and other synthetic blue dyes, numerous small communities such as these keep the practice of indigo production alive through their own local and specialized methods of dyeing and textile creation. All of these methods, however, must account for indigo’s unique properties as a dye.

Indigo

Preparing fabric for batik dyeing with indigo. Image courtesy of iStock.

Unlike many natural dyestuffs, indigo does not require the addition of a mordant—another substance, usually a metal salt—to fix the color to the fiber. The brilliant blue dye extracted from plants also will not directly color any material.

Instead, indigo has an intriguing dye process that is unlike almost any other. Indigotin is the proper name of the blue pigment in indigo-bearing plants, but it will not act as a dye unless first dissolved in an alkaline (basic) solution. This turns the pigment into leuco-indigo (also known as “indigo white”), which is yellowish-green instead of blue. The dye will fix to the fiber in the indigo-white solution, and then exposure to air will convert the dye back into the recognizable blue of indigotin. Indigo dyers have come up with a number of original ways to facilitate this process, which usually takes place in a large vat that will be used repeatedly to dye cloth and fiber.

Even though indigotin is the pigment present in all indigo-bearing plants, the exact color of the dye derived from different plants may vary. This is likely due to the presence of other compounds present in the plants (such as indirubin, also called “indigo red,” or flavonoids that add a yellow tinge), which can affect the color. Synthetically produced indigo dye does not have such a great degree of variation, as it is almost entirely pure indigotin.

Indigo

A step-by-step collage of indigo dyeing, from plants to finished fabric. All images courtesy of iStock.

Whatever the source, and whatever the tradition, it is hard to resist the allure of the rich and satisfying blue of indigo. Whether it’s the ikat textiles of Asia, the copper-like brilliance of saturated Touareg cloth, or even your favorite blue jeans, indigo continues to entrance and inspire. The universality of our love for the color blue will likely keep natural indigo dyeing alive for generations to come.


Further Reading

Indigo by Jenny Balfour-Paul (Archetype Books, 2007).
Indigo: The Color that Changed the World by Catherine Legrand (Thames & Hudson, 2013).
A Handbook of Indigo Dyeing by Vivien Prideaux (Search Press, 2012).


Leslie Ordal writes and works in healthcare research in Toronto, Canada. She plans to resume blogging about her fiber adventures soon at www.leslieordal.com.


Learn and Do: The Dyeing Process

 

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