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Indigo and the ancient craft of dyeing

  • December 18, 2010
  • Marybeth Kampman
  • ALONG WITH BEING overwhelmed by the differences in culture and lifestyle on a recent trip to Vietnam, I was taken by the country's natural beauty and its wealth of exquisite textiles. I have always loved textiles and plants. It wasn't until this trip that I was hit with the realization of their interdependence. Many textiles are made from plants -- cotton, hemp, linen -- and they often get their beautiful colors from dyes made from other plants.

    While trekking behind my Hmong guides along the path leading out of Sapa, I admired the beauty of their native outfits. Their dark blue pleated skirts, scarves and belts were intricately embroidered. As much as I was taken by the beauty of the embroidery, I was also drawn to the intense blue color of the garments.

    I peppered our guide with questions about the plants we saw along the path. When our guide pointed to a field of low-growing, green leafy plants and stated that it was the indigo plant, I became determined to find out all I could about how these plants produced the deep radiant blue color of the fabric I saw hanging outside of the village homes.

    On the porches of many homes we passed were large barrels filled with a thick blue liquid, the indigo dye bath in which fabric was dipped until the desired color was achieved. My guide made the dyeing process sound simple. When I returned home I researched the indigo plant's transformation from a plant to a dye.

    The name indigo comes from the Roman term "indicum," which means a product of India. However, the plant is grown around the world in Asia, Java, Japan and Central America. The color blue has long been associated with power, magic and divinity.

    Indigo has been used as a dye throughout the ages. It was known to the ancient civilizations of Mesopotamia, Egypt and Greece. It is special in that it meets the two most important qualifications of a dye: it must be able to be absorbed by the material one is dying and the color must be absolutely "fast" or last as long as the material it dyes. In other words, it must be fade proof. It can be used to dye animal- and vegetable-based fibers with equally good results, although the process is a little different.

    Indigo belongs to the legume family and more than 300 species have been identified. The source for indigo dye or true indigo is Indigofera tinctoria and is native to the tropics. In temperate climates indigo can also be obtained from dyer's knotweed Polygonum tinctorum, although the Indigofera species yield more dye. From my research it's likely the indigo I saw growing was Polygonum tinctorum.

    Indigo is an excellent rotational cover crop for increasing soil fertility. It usually yields two harvests, in June and October. When harvesting one needs to be careful to cut the plant two hands' breadth above the ground. If cut too low it could injure the young shoots that come up from the root and yield a fresh harvest in two to three months.

    If you were to put the leaves of the indigo plant into a bucket of water and expect to get a beautiful blue color you would be sorely disappointed. Indigo is insoluble in water. Indigo is unique in the plant kingdom in that it is a "substantive dye," which means it needs to undergo a chemical change brought about by fermentation in order to produce color. Indican is the chemical found in the plant leaves. Indican needs to be released from the plant leaves through fermentation to produce indigo.

    After harvesting, the plants are laid in wooden troughs or vats filled with water and left for several hours until they are completely saturated. There are ways to encourage the fermentation process, including the use of additives such as lye, urine, lime and rice wine. You can tell the fermentation process is occurring by the presence of fine bubbles and a strong smell. The entire surface of the vat becomes covered with a thick layer of scum.

    Once the dye bath is ready, the fabric is immersed into it and stirred for variable amounts of times determined by the darkness of the blue color desired. When a fabric is removed from the dye bath, the indigo quickly combines with oxygen in the air and oxidizes. This process produces the dark blue color, which is colorfast.

    The darkness of the blue color is achieved through multiple dippings and oxidization. Cotton fibers take up the dye much slower than wool, therefore it may take many dippings to achieve the desired dark color. The residents of each community we passed through could be recognized by the distinctive shade of blue of their garments, according to my guide.

    My research left me overwhelmed with respect and admiration for the Hmong people who perpetuate this ancient craft of dyeing. Synthetic indigo dyes and modern dyeing methods have made the craft all but obsolete. I can't help but muse that like the Hmong women, we, too, depend on indigo to determine our fashion identity. It is indigo dye that colors our denim jeans.

    The University of California Marin Master Gardeners are sponsored by UC Cooperative Extension. For questions about gardening, plant pests or diseases, call 499-4204 from 9 a.m. to noon, and 1 to 4 p.m. weekdays, or bring in samples or pictures to 1682 Novato Blvd., Suite 150B, Novato.