Indigo Dye

It’s pleasant, from where I write this post in my ice-bitten and wintery grey state of Pennsylvania, to look at this lovely plant. Here is _Indigofera tinctoria_ the most important plant to make the dye colored indigo — a color that meant beauty to some, but misery to many others.

Indigo is one of the oldest dyes humans invented — you can see a photo with vats of the vibrant hue in the second image. In 2007 small cotton scraps with this coloring were found in Peru that dated to 6,200 years ago. (I enhanced the shade in the third image for visibility.) It was also produced in Ancient Egypt and Edo Japan as well as other places. Most famously, indigo was made in India, the region being so synonymous with the hue that it gave the dye its name to the Ancient Greeks, and through them, eventually to the English.

Indigo is special in that it does not need a mordant to set — most other dyes needed these special substances to fix their colors in a fabric. Oxidation of the indigo that physically mixes with the fabric is what gets the vibrant blue shade to set. (Well, okay, full disclosure — you also need something to raise the acidity and something to help the indigo liquid to be “reduced” of oxygen.)

Indigo was in such high demand that during the U.S. history when slavery was allowed, it was called “blue gold” — it was one of South Carolina’s key cash crops in the 1700s. Plantation slaves worked under brutal conditions to harvest the indigo plants. European colonizers in Southeast Asia also forced indigenous workers to grow indigo, leading to rebellions in some places.

By 1880 Alfred Bayer managed to synthesize the color with modern chemical methods — this was a time when many color dyes were synthetically created. We take for granted the wild hues we see on fabrics today, and the wealth they once symbolized, as well as the toil they cost.