A Novice Dyer Tackles Indigo

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By J. Michael Quante, AATCC Science Editor

Dyes are old acquaintances of mine. Trained as a natural products organic chemist, I once spent hours in the lab extracting, modifying, and creating various molecules to get chemicals with just the right properties for the work I was performing. I especially enjoyed dabbling in dye chemistry; isolating dyes from plants, synthesizing them, or attaching them to various bioactive systems for monitoring. After all, the history of dyeing was entwined with that of organic chemistry after Perkin first synthesized mauvine in 1856.

Indigo fabric dyeing has been part of the human experience for at least 4,000 years. From use of plant- derived dyes to synthetic dyes beginning in the 19th century, today the pendulum is swinging back to use of the plant-derived dyes again. Recent developments in “green” indigo synthesis may also offer a sustainable source of indigo that doesn’t involve hazardous chemicals for its synthesis or reducing agents for the indigo dyeing process.

After years as a practicing chemist and working at AATCC, I still lacked the experience of dyeing fabric with natural dyes.  I finally had my opportunity this January by taking the “Natural Indigo Dyeing Basics” class taught by Diana Cathcart of The Textile Creative at the Durham Arts Council, Durham, NC, USA.

There are many methods of natural indigo dyeing, including fermentation and urine-based methods. In our class, we used Michel Garcia’s 1-2-3 glucose vat dyeing method. We used 1-part indigo powder extracted from the locally-grown plant (Indigofera tinctoria), 2-parts pickling lime (calcium hydroxide), and 3-parts fructose in a small canning jar containing warm water as our indigo starter. After 45 minutes, the light greenish- yellow solution (containing the water soluble leuco indigo) above the sediment indicated we were ready to dye fabric. We dyed both silk and a cotton-hemp blend fabric using various resist dyeing techniques to form colorless patterns on the fabrics.

The first lesson we learned: success requires patience and experimentation! Natural indigo dyeing is a finnicky process.  The bath temperature, pH, and minimizing bath agitation are all critical factors. Since the soluble leuco dye is sensitive to air, fabric must be slowly added and removed from the bath. Upon fabric removal, the greenish-yellow color turns to blue as air oxidizes the leuco dye to the insoluble indigo. The various resist dyeing techniques (e.g., tying portions of fabric with twine and even clamping with clothes pins or paper clamps) used by the students created fabulous designs!

I must say that my first experience with dyeing was very satisfying.  It also reminded me how much the natural world has been both the source of inspiration for human innovation as well as a wellspring of resources bestowed on us as precious gifts. With these insights in mind, we can move forward in our efforts to conserve and wisely reuse our limited natural resources, all the while adding color to our wardrobes.

(All photos credit: Mike Quante, AATCC)
Opinions expressed in this blog post are those of the author and not necessarily those of AATCC