Indigo is more than just a colour: it is a natural dye that has had a profound effect on the history of textiles globally. The production of indigo dye is a complex and capricious process which results in a beautiful, intense colour that does not lose its hue when washed. A variety of techniques can be used to introduce pattern into the cloth; from simple tie-dye motifs to more complex hand-drawn wax resist designs.
Growing and producing the dye
"Indigo" is a natural dye but it does not come from just one plant - more than 300 plants from different genera can produce the dye when processed properly. The growth of these plants is widespread, and as a result indigo dyeing techniques appear in traditional textiles all over the world. However, it can be a difficult crop to cultivate, susceptible to climate, disease and insects.
Once harvested, the next step it to extract the dye - itself a complicated process. The most intense colour is produced by fermenting the leaves in a solution and agitating the mixture. On a commercial scale, this was done in large tanks, with people wading through the solution and beating it to oxidise the pulp. The final step was to drain off the liquid, dry the pulp, and cut into blocks for transport.
Trade and industry
As dried indigo dye blocks were small, of high value and easy to transport, the import and export of indigo was a hugely profitable industry. Prior to the 16th century, the dye known as woad (isatis tinctoria) was the principle blue dye grown and used in Europe. This dye is the same as indigo but is of a lower concentration and was primarily suited for dyeing wool.
With the Spanish conquest of America opening up global trade routes, there was an increase in demand for the more intensely-hued true indigo dye. Indigo powder was worth more than any other "spice" (as it was classified on shipping lists) and unscrupulous traders would often add sawdust, sand or moisture to increase the volume.
The European woad industry tried in vain to compete with the appetite for true indigo, alleging that it corroded and destroyed the cloth and was poisonous to those who used it. The real danger lay in the production process. In South Carolina, where the American production of indigo was centred, slaves who waded through the noxious dye extraction pits often fell ill and died. The abolition of slavery in the 1860s finished the American industry, and by the end of that century a synthetic indigo dye was developed in Germany – most familiar today as the dye used for blue jeans.
Dyeing with indigo
The most captivating aspect of indigo occurs during the dyeing process. Indigo powder is dissolved in an alkaline solution, in what is known as a vat. Cloth is submerged in the dye bath for a few minutes at a time, and when removed is a dark yellow-green colour. Within a few minutes, the cloth almost magically transforms to blue as it is exposed to the air. Subsequent dippings increase the hue and allow for patterns to be created through a variety of different techniques.
The warm indigo dye bath is perfect for the Batik, or wax resist, method, which involves drawing on to the cloth with hot wax. Once the wax hardens, the cloth is dyed and then the wax chipped away, revealing the pattern in the original colour of the cloth. In the tie-dye technique, known as shibori in Japanese, sections of fabric are gathered and tied or clamped before dyeing. These methods can be used to create a variety of patterns, from bold geometric designs to sinuous lines and starbursts.
The Auckland Museum collection also holds some fine examples of Indonesian ikat fabrics dyed with indigo, in which the threads themselves are tied and bound before dyeing, the final pattern revealing itself in the weaving of the cloth.
Cite this article
Indigo. Auckland War Memorial Museum - Tāmaki Paenga Hira. First published: 21 October 2015. Updated: 22 October 2015.