Indigo: A Natural Dye Helped by Something Gross Quiz

Answer: yellowish, green then blue

Indigo dye must combine with oxygen before it shows blue, so when the fiber to be dyed is first brought into the air, it's whitish or pale yellow. As it picks up oxygen from the air, it turns into the blue indigo we're expecting to see. The magical transformation is unusual in natural dyes, which usually appear a little darker than their final shade.

The color of a brown or red may need to be darker when it comes out of the vat, to compensate for the fabric being washed out and dried, but the color change is nothing like indigo's.

Answer: Eliza Lucas Pinckney

Eliza Lucas Pinckney (1722-1793) experimented in the early 1740s with seed her father sent her while he was away in Antigua, and with the help of some of her slaves who had grown indigo in the West Indies and west Africa, who never get any credit by name, she produced a seed crop in 1844 to distrubute. By 1748, South Carolina was exporting 130,000 pounds of indigo, and the amount continued to increase, adding significantly to the wealth of the state.

Answer: stale urine

Wood ashes were useful for making soap, tannic acid for tanning, and vinegar needed to be made from apple cores or some other byproduct. Any of the three could be used instead of urine in the indigo process. But if old urine was just sitting around waiting to be discarded, it could be used as a useful and cheap substitute instead. Once the indigo was dissolved in urine, the mixture took on a greenish color, and could be used repeatedly until the indigo in it was all used up. And yes, it smelled just as bad as you're picturing.

Answer: True indigo, Indigofera tinctoria

"Indigofera" meant fertile plant from India, which described all of the genus, and the species "tinctoria", in particular, would go to a dyer because it contained the most indigo. Woad was another plant which yielded a blue dye, the most of its genus, but still not as much as true indigo, which outcompeted woad as soon as dyers had a choice. Knotweed, from east Asia, was the favored indigo plant of its genus there, until once again, true indigo was introduced and took over.

The only limitation on true indigo was that it had to be grown in a warm climate, like India or South Carolina, but indigo could be dried into cakes and shipped in a solid form, which made it especially valuable, because warm areas could send it to cold ones and outcompete whatever dyes that dyers in the cold places were buying from farmers locally.

Answer: horribly stinky, potentially unheathful

Processing indigo required fermenting it, which produced an awful odor, which processors -- generally slaves -- had to be around constantly, even standing in vats to mash them down. John Woolman, an abolitionist Quaker, refused to weear dyed cloth, believing that slaves suffered health damage while dying it. James Roberts, a Revolutionary War soldier, wrote, "Such is the effect of the indigo upon the lungs of the laborers, that they never live over seven years." However, historians failed to find a statistical correlation with a shorter lifespan or more diseases, though all agree the smell is awful, and further work may point out health problems. (Credit to "The Devil's Blue Dye: Indigo and Slavery" by Jean M. West)

Answer: India

India was the original place where true indigo, Indigofera tinctoria, was found, but seeds for the same genus and species were spread worldwide and much effort was put into perfecting cultivation and breeding the best plants by countries around the world. Still, India held its reputation as the producer of the best dye. Among the New World colonies, Guatemalan and French West Indies indigo was considered superior, but it still couldn't surpass India's.

Answer: more impurities could appear, usually causing a green tint

When more plant material needed to be used, there was a risk of more impurities in the plant being exaggerated in the dye bath and affecting the color, no longer giving the pure rich blue that dyers wanted. A greenish tint was most common, perhaps because impurities tinted the bath yellow.

A bluish green color that might be considered acceptable under other circumstances wasn't what indigo dyers or fabric buyers wanted. Dyers knotweed or West Indian indigo were examples of plants that could dye well enough, but were outperformed by true indigo.

Answer: spread rumors, got rulers to ban importation and got dyers to swear they didn't use it on pain of death

Woad dyers convinvinced Elizabeth I of England, Henry IV in France (and their successors) and the German government to ban or severely control the importation of indigo from India in the 1500s and early 1600s. Eventually, true indigo was grown on colonial plantations in the West Indies.

By the 1600s, countries were investing there and they were less interested in supporting the woad growers with legal prohibitions, but the transition was a slow process, lasting well over a hundred years, and not led by woad growers. Woad is still grown as an historic curiosity, as a potentially useful plant in medicine and as something that home dyers can use.

In the southwest continental US, it grows so well that it is considered a noxious weed to be eradicated.

Answer: the leaves will dye about 1/3 their weight in fiber

This will have all the usual warnings: it depends on which fiber, how dark a shade of blue, how well fertilized and healthy the indigo plant was, and all those usual warnings, but in general, indigo leaves could dye a third of their weight in fiber, more or less. Woad, which was an example of a plant that produced less dye, could only dye about a tenth what true indigo could -- again, with all the caveats about how much a plant would dye.

Answer: around the 1890s

Adolf von Baeyer of Berlin, not the aspirin fellow, worked on developing synthetic indigo, and though he succeeded in the 1860s, the results weren't commercially profitable. Many others followed, and finally, Baden Aniline and Soda Factory (now BASF) succeeded.

The transition was fast: 19,000 tons of natural indigo were produced worldwide in 1897, but only 1,000 were produced in 1914. Today, synthetic indigo accounts for 95% of indigo's total usage, with just 5% still coming from plant leaves. No worries! Our blue jeans never touched stale urine. Whew!