Blend for another minute, and once again strain the green liquid into the dye bath. Fill it again half-way full with cold water and a few ice cubes. Return any strained indigo leaf to the blender. Strain the green liquid into the dye bath, using a fine mesh strainer or cheesecloth. The water in the blender should be dark green, with some white froth on top. The colder the water is, the more time you will have to finish straining and building the dye bath before the reaction starts.Īdd the dried indigo leaf and blend for 1 minute. Weigh out 100% weight-of-fabric (WOF) of dried indigo leaf.įill a blender half full with cold water-you can use cold water from the tap or, if you have it, cold water from the refrigerator.Īdd a small handful of ice cubes and blend for 30 seconds. Let the fibers cool to room temperature, then squeeze out excess water while wearing rubber gloves (you do not want to the oil in your fingerprints to attach to the newly cleaned fiber). We usually have a second dye pot full of hot water, heated to the same temperature as the scour bath, to plunge the fibers into. This will prevent thermal shocks that damage the fiber. Hold for 30 minutes, stirring regularly but gently (you do not want to felt your wool).Īfter half an hour, lift the fiber out with tongs and rinse in hot water that is the same temperature as the scour bath. Raise the heat to 160F (for silk) or 180F (for wool or alpaca). Alternately, use a product sold specifically as a wool scour or silk degummer. Add a teaspoon of PH-neutral detergent like Synthrapol. Using fresh indigo leaves it is possible to achieve beautiful shades of turquoise and ice blue, without needing to build a reduction vat.įor protein fibers (wool, silk, alpaca, etc.): Scour with a PH-neutral detergent or a wool scour.įill a dye pot 3/4 full with warm water. Any wool or silk soaking in the water while this reaction occurs will be dyed blue, too. As the cold water warms up, the beta-glucosidase cleaves the indican into a molecule of indoxyl, and the indoxyl reacts with oxygen dissolved in the water to form blue indigotin. They can later be blended with ice water to mix the precursor compounds and begin the chemical reaction leading to blue indigotin. If high-quality indigo leaves are harvested very carefully, the two precursors are preserved even after the leaves are dried. This may have evolved as a defense mechanism against predation, although the evidence is unclear ( Daykin 2011:5). If the leaf is damaged by grazing herbivores or gnawed by insects, the precursors are mixed together and blue indigotin forms. Instead, it exists in the form of two precursors, beta-glucosidase and indican. Indigo does not exist in the plant in the form of blue indigotin-otherwise the plant itself would be blue. However, it is possible to short-circuit this laborious process by taking advantage of the chemistry of indigo leaves. When fabric is removed from the vat, the dissolved indigotin oxidizes and comes back out of solution, bonding immediately to the fiber. The traditional method of applying it involves fermenting the leaves, extracting the dyestuff, dissolving it in a reduction vat, and then dipping fabric in the vat. Boiling it in hot water will have no effect, because the blue coloring compound indigotin is insoluble in normal water. Indigo is unique among all natural dyes in how it attaches to fiber. Today indigo is still the most important blue dye for clothing and jeans, but almost all of it is synthetically produced indigo, not indigo extracted from a plant. This lead to the collapse of the indigo-growing industry. However, a German chemist identified the chemical structure of indigotin and discovered how to synthesize it in 1883 (ibid:542). South, especially around low-country South Carolina and Georgia, which have subtropical climates ideal for growing indigo. It was one of the major exports of the antebellum U.S. Natural indigo was a major global commodity in the 18th and 19th centuries, and industries sprang up all across the world. It has been the most important source of blue dye for much of recorded history, and there is archaeological evidence that indigo was being used to dye fabric up to 4,000 years ago in India. Indigo is now cultivated world-wide, but is probably native to South Asia (Glowacki et al. Natural indigo is extracted from the leaves of indigofera tinctoria, a short shrub that is a member of the legume family.
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