Growing & Making Fermented Indigo Dye

fermentation, wildcrafting

My hunch without knowing the real story is that the plant indigo’s blue dying capabilities were discovered by noticing its damaged leaves. Insects chewed bits and pieces of the plants grown at the farm this past year and the color change was distinct, like a little window into the color capabilities it had.

Indigo is so cool, I’m learning as we get to know each other. Her processes rely more on observation and play than perfectly calculated math recipes. Our first attempt made a rain cloud gray color, though through nudging some variables around we eventually got those storms to pass and opened up some delicious turquois blue skies. Indigo also requires two fermentation processes- the first is complete when the indigo says it is, and the second is concocted and tended to with the care of a sourdough starter. A fermenter will be at home with indigo.

Japanese Indigo is in the buckwheat family and looked very much like smartweed, only bigger. It was easy to start from seed but seemed to need a long growing season. This year it’ll get started indoors in March instead of April like last year. Some say you can get two harvests of it in a season, not sure I saw the opportunity for that as mine didn’t size up well until maybe September, and then when it flowered saving seed became a race against the first frost. The plant grew well in our unirrigated fields and needed no special attention aside from the usual.

After cutting down the indigo (which I heard varying accounts of when to, like before they flower or right before they seed- which I went with the latter) the whole plant was stuffed in a 44 gallon NSF Certified Brute garbage can that has retired from fermenting wine, and topped with enough water to cover and weighed down with a rock plopped on top, nothing else added. A handful of plants were partoned in the field to finish their cycle of producing seeds for the follow year’s indigo.

The fermentation took place indoors at relatively 70 degrees since the outdoor fall temps we’re dropping to the 40’s at night. Without much delay fermentation started bubbling along and gradually the liquid got an increasingly inky appearance and smelled just about right. It was decided that the fermentation was complete when looking at the leaves they appeared noticeably spent of their color- that’s the best way to describe it. This was easy to see when comparing the leaves that looked drained compared to some leaves trapped on the inside of the indigo pile who still retained a full liveliness. It’s probably noticable between the accompanying photographs.

After yanking the plant parts out of the Brute and tossing them onto the compost pile, I began to aerate the liquid by taking a bowl and repeatedly filling and dumping the greenish water. The idea here is that in the presence of oxygen the pigment precipitates down to the bottom. Sounds about right to me- after ten minutes of splashing followed by a few minutes allowing it to settle, the color was clearly in a pile collected at the bottom. The greenish liquid has become yellow.

At this point the top liquid was carefully scooped out until it could fit in a 5 gallon bucket. The precipitated pigment was stirred back into the liquid so the whole thing could pass through a seive to get out any remaining plant chunks. When the pigment settles back to the bottom it can be further scooped off and then dried into a paste or a powder or saved as is in a jar, or it can be carried on straight to the final phase in the dying process which so many affectionately call the vat.

I knew nothing of a vat prior to this experience and have been thrilled by its relation to many of the other starter cultures kept around the house. It reminds me most of a sourdough starter in that it is a living organism that needs refreshed prior to use, can go dormant, and preforms best when in its most fervently active. 

Here’s as far as I understand it: at this point the indigo pigment is a separate thing in the vat, like rocks in a bucket of water. Therefore the indigo needs to be dissolved so it can cling permanently to the fibers, and in order to do that it needs a couple things:

First is an addition of either lime or wood ash or lye to create an alkaline environment that falls somewhere between a pH of 9-10 and makes the bucket smell like you’re baking pretzels. Before this step my indigo would only turn any fabric gray. This is an intuitive guess but without a pH meter, like before pH meters were made, perhaps lime/ lye was added until the desired color was produced. Relating note, I had given up this dying attempt after only getting gray. Eventually this dyed sock (below) found its way into the laundry and made it through with full color intact. After discovering that, it reinvigorated the desire to figure out this indigo thing, now with a really nice pH meter. Using that same vat but with a corrected pH, you’ll see the lovely sky blue that came of it. Who knew?

Next is to create an environment absent of oxygen, because as previously mentioned, with oxygen present any dissolved indigo would precipitate to the bottom. Recognizing that when making wine for instance, a vigorously active fermentation is when it is most protected from oxygen, a vigorous fermentation should do the trick! So in went all the weird sugars in the cabinet- old brown rice syrup, some molding maple syrup, a dump of white sugar- cause heck, and a healthy splash of happy sourdough starter. Yum. 

Lastly is a good warm temperature. Perhaps in a natural setting this is best done quickly after harvest to cash in on the summer heat. I saw the best results with my dye the hotter I could get it, which was around 100 degrees. Going too hot would start killing the microbes so it’s worth being mindful of that. With a 5 gallon bucket it’s a challenge to keep it warm so I wrapped it in a borrowed seed heating mat and that seemed to do good enough.

After a couple days the vat was bubbling away wonderfully. I prepared a clean white cotton cloth by soaking it in water and ringing it out then dropped it in the vat, carefully trying to not distrub the liquid enough to introduce any unnecessary oxygen. After a few minutes I checked it and started getting a nice blue. What’s neat, as indigo dyers will tell you, is that indigo realizes its blue color on fabric as it is reintroduced with oxygen so upon immediately taking the fabric out of the vat you get to watch the fabric fade into blue. Neat. After a couple plunges with water rinses inbetween it seemed that the strength of the dye I have makes a lovely light, turquois blue. The vat then proceeded to dye a few other peice of clothing before getting retired with a lid on it to hibernate in a corner until the dying urge returns, and the pH is re-limed to standard, and the fermentation reawakened to dye again.