I find joy in the color blue… more specifically, I find joy in dyeing with indigo. Each time I pull a piece out of my dye vat, I am in awe of the magical transformation. Like many avocational dyers, I order my natural, processed powdered indigo for my dye vats from a supplier. Then I learned that indigo can be grown in this region, and that one type, Japanese indigo, grows especially well here. How wonderful to learn that indigo grows in the Folk School’s new dye garden for upcoming classes.

I was interested in those classes, but with the onset of the COVID pandemic, however, classes were canceled.  I contacted Folk School Resident Artist for Dyeing, Martha Owen, and Farmer Teddy with a proposal: if I could be given some of the fresh leaf indigo, I would explore possibilities for use of that indigo, and would share my results with them, and with anyone else interested. They agreed, and we are grateful to Farmer Teddy for his hard work, generosity of knowledge, and for the indigo he trimmed and gave to us, carefully measured for his records.

From this point on, “I” turned into “we”: I invited my good friend and studio partner, Cathy Mulvey, to join me in this effort. Safely distanced when inside, working outside on the studio patio as much as possible, we were able to do so much more together than I had even anticipated.

Our first effort was to challenge ourselves to understand how the indigo powder that we buy is processed from the plant, and to do it ourselves. Our goal was to learn and appreciate the process, not to start providing our own. This is a summary of that first exploration for us.

First, we read and studied. We wished we had taken more chemistry in school, or perhaps we wished that we had retained what we had been taught.

It seems that there are 2 primary means of extracting indigo from the plant: vat fermentation and composting. It was interesting to attend a symposium by the NC Arboretum, Growing Color, to hear indigo growers Sarah Bellos and Rowland Ricketts speak about these processes, steeped in history. And it was clear that the composting method was not for us, so fermentation it was! YouTube videos by Donna Hardy on Ossabaw Island and by Ninja Chickens gave us insights specifically into indigo fermentation extraction, as well as the book Singing the Blues by John Marshall.


DAY 1:

We met Farmer Teddy at the Folk School Garden on a day he was planning to cut back some of his Japanese indigo. He was hoping that regrowth would occur without the plants going to seed right away. He gave us the cuttings from 16 plants (stalks with leaves), with total weight of 13.5 lbs.

Within a half hour, we had the indigo back at our studio and divided the lot among 4 5-gallon buckets, with 3–3.5 lbs of stalks with leaves in each bucket. The only addition was warm water, and we placed a heavy rock on top of the plant matter to keep it submerged. Our goal was to maintain the water temp 90-100 degrees F in each bucket for most effective fermentation. Two buckets were heated with external heating pads wrapped with insulation, and two buckets were heated with aquarium heaters….simply because those were the devices we had on hand. We placed a cover on each bucket.

DAY 3:

We had been keeping the vats covered and warmed, maintaining temps in the mid 90s. Today, they were just beginning to put out an odor. The surface appearance was a bronze metallic sheen with teal bubbles; what we could see of the liquid below was dark green. We regularly checked temps.

DAY 4:

The vats didn’t appear much different than the day before, but the odor was much stronger: Dirty feet? Rotten potatoes? Spoiled fish?

DAY 5:

Oh, dear… did we wait too long? Fermentation has definitely occurred, and we knew that if it was allowed to go too long, it would begin to use some of the indigo precursor, so we might have lower yield. Nothing to do but forge ahead.

We carried the 4 buckets outside and removed the slimy yellowish plantstuff.

We then drained the dark teal liquid of each vat through a paint can liner, and combined the liquid into a rectangular 95 quart opaque tub, chosen for its size/depth and for better visibility of the liquid. (We had always planned to combine the liquid, and had originally separated it into buckets for greater ease of heating with the equipment we had.)
Next step was to make the liquid alkali and to aerate it; there is mild controversy over which to do first, but we went with the majority of instructions found, and used pickling lime to take the pH from starting point of 4 to 10; 7 is considered neutral.

We needed to introduce oxygen into the system for indigo’s interesting chemistry to be on the right path, so Cathy used a metal paint stirrer powered by an electric drill to aerate the liquid for ~ 30 minutes. And then, for good measure, we did ~ 60 bucket exchanges for maximum oxygen introduction.

By this time the liquid was a dark blue with slight greenish cast, with minimal foam. Flies were beginning to swarm, so we moved the tub into the studio. We covered it with netting, to keep out larger insects and my dogs, but allow air flow.

Our expectation at this point was that the molecules from the plant were finally at the point to be considered indigo, and would now begin to precipitate down to the bottom of the tub. We wanted to watch… sort of like those old ant farms, remember? Well, maybe not.

By later that night, the surface of the liquid appeared brown, with unidentifiable brown stuff floating. Could that mean that the indigo was just starting to move downward?

Now to wait.

DAY 6:

Yay! The top 1.5” if the fluid in the vat was yellowish brown, while the remaining liquid below it was blue. We assumed that this was the beginning of the slow precipitation process. Our plan was to decant the yellow-brown waste liquid from the top without disturbing the blue beneath.

DAY 8:

A nice surprise: When Cathy and I began to decant the brownish liquid from the surface, we were anticipating skimming off ~ 2”. But there had been some sort of optical illusion, and we were able to remove much more, showing that the indigo was indeed precipitating down. The pH of the waste liquid was 8, so it didn’t take much vinegar to bring it to neutral 7 before we disposed of it.

DAY 9:

Cathy and I decanted several more inches of amber fluid from the top of the tub (pH of that then neutral 7), but when we began to see blue, we decided it was time to begin pouring through a strainer setup. We lined a colander with 2 layers of 8 mumme silk habotai fabric, and placed it over a 5 gallon bucket. We then poured a cup or so of blue vat fluid in at a time. We continued to add this thick indigo liquid as the level in the strainer receded, but at time intervals. It didn’t occur quickly. After 3 hours, there was still a fairly high level of indigo sludge in the silk/colander, with more in the tub to be poured; the rest would have to wait until the next day. The pH of the wet indigo was 8.5.

DAY 10:

When we finished pouring the indigo liquid into the silk/colander, we tied the silk as a bag, and suspended it for final dripping for a few hours. We then laid the silk flat on a drying rack and spread the indigo paste more evenly across the silk to facilitate drying. The overnight drying was to take place indoors, since a squirrel had made itself at home on my studio patio.
The waste liquid then appeared to contain some blue, so we let it settle for the possibility of a pour-through with another piece of silk.

DAY 11:

Cathy and I decided to take the drip bucket from the first pour-through, and do another, into fresh silk. Yes, there was a bit of indigo there.
The indigo paste we spread yesterday is still drying.

DAY 15:

Today we determined that the indigo paste on the silk had dried sufficiently, so we gently shook/rubbed it off the silk into a wide dry bowl. Most was in the form of dense hard chips, and needed to be ground with a mortar and pestle.

Total yield from 13.5 lbs of plant: ½ cup of powder by volume, 3 oz by weight

Two weeks from plant to powder!


This was an exciting first trial for us, but a few things we might have done differently:

We don’t think we let the initial fermentation go too far, but we probably could have moved to the next step by Day 3 or 4.

This might be an interesting additional demonstration for dye classes during the course of a typical week at the folk school, during indigo season, but it would need to occur essentially within a 5 day period for the entire process to be observed. Could we do that with smaller amounts of plant and still get enough powder to show?

Bless the folks who provide us processed indigo powder!

So now what else can we try with fresh indigo? And what could we try with leaves we have dried?
More indigo, please, Farmer Teddy!

We are grateful to the John C. Campbell Folk School, especially all those involved with establishing the new dye garden.

Thank You,
Sally Blankenship and Cathy Mulvey

Sally Blankenship
About Sally Blankenship

Sally Blankenship is a fiber-dabbler, with interests including dyeing, batik, spinning, felting, weaving, and botanical printing. She has a passion for blue, particularly indigo, and takes joy in its exploration. She likes nothing better than to share the wonders of this incredible natural dye.