(I have posted about this on @official-nature-posts before but asking you specifically. So when I remembered that Japanese indigo is a persicaria, I wondered if my local Persicaria Decipiens would work. I could see some blue hints just crushing it up which is good, best seen in the blurry photo. I plan on doing fresh leaf dyeing first, but I have been reading up about small scale indigo vats which id like to know if you know much about them? I don’t want to have to buy chemicals.I know that they need an alkali (I can wood ash lye or even calcium hydroxide at a pinch by heating up ashes a lot) a reducing agent ( fructose, I saw one blog that was using boiled orange peels and also trying pectin.) and of course the indigo source. Do you know how the reducing agents work. I will wait a while for it to warm up so the plants start growing again because they get knocked about by frost each year. Also hopefully going to grow some Japanese indigo.
Ooh, cool! I've gotten to try indigo dyeing on a course once, and one of my friends there showed how to make an organic dye vat, Michel Garcia's style (you can find his tutorials on youtube too!). Both were made with ready indigo powder, though. Let's check my notes first, then I'll talk about the plants. Prepare for a long read!
For reference, the normal chemical process went like this: we used 10% WOF (weight of fibre) sodium hydroxide to get a high (10-11) pH to help extract the dye. Temperature should be 40-50⁰C., and the extraction time was 40 minutes. For the reduction, we used sodium dithionate 60% WOF at 55⁰C (no higher, it wastes some dye), and pH was 8-9. At that step we had to leave the room for 30 minutes because it's toxic to let it settle. A tip for controlling the temperature: use a double boiler. After the 30 minutes, it looked like this:
A pretty metallic sheen on the surface and an "indigo flower" bubble in the middle had formed! Underneath the mixture was a yellowish green.
For dyeing, dip it 1-10 minutes, try not to get air mixed into the dye bath. We used a parsley boiling kettle with its basket to dip the fibers in! Presoaking in water also helps the dye absorb more evenly. Pulling it out is magical, as it oxidized it turns from green to blue! Then rinse with vinegar and water and continue rinsing with water.
This method can be done in smaller scale! It works like this:
2 parts calcium hydroxide (pickling lime) for alkaline agent
3 parts food-grade fructose or any other natural reducing agent (henna, oignon, very ripe fruits or an old madder dye vat are some suggestions!)
The indigo powder was dissolved into a bit of water first by putting it into a plastic box with some marbles and shaking it around to form a smooth paste.
For the reducing agent, the fructose was simply dissolved into 7-8 liters of water. If using henna (Lausaunia Inermis), prepare a "decoction" by putting the extract in cold water and boil till the powder remains in the bottom, then filter through a cloth and let cool to 50-70⁰C.
Then the indigo paste was added to the reducing agent. Probably let this sit for 40 minutes too?
For the alkaline agent, also don't breathe or touch with bare hands. Dissolve the calcium hydroxide in warm water and add that mixture into the indigo dye vat, carefully pouring it along the container wall to avoid getting air mixed in. Stir three times, creating a vortex. It should turn green, and look like the picture above with a metallic surface and blue bubbles. Then cover the vat tightly and let sit for 12-24 hours for the indigo to dissolve and reduce. Then carefully stir it and check the pH. Adjust it if needed:
For wool, pH 10 and temp 40-45⁰C.
For silk, pH 11 and no heating necessary.
For celluloce fibers like cotton/linen, pH 12 or higher and no heating necessary.
Dyeing: With presoaked fibers, dip for 30 minutes. Press the fibers against the wall of the container to avoid getting air = oxygen into the dye bath. At this point, it should look green.
Then the dye needs to be oxidized. To do this, remove the fibers from the dye vat, gently wring excess dye out, and push it in and out of cold water, opening any folds as you do. After the colour stabilizes into blue, hang it to dry for 30 minutes.
For best results, repeat this dyeing process two more times. If you want darker, extend the dipping and drying time on the second and third dye round to 1 hour and 1.5 hours.
When using fresh plants, I think you can extract the dye first and then use the extracted and filtered solution (or paste, if you use a lot of leaves and dehydrate it a bit) as a base for the fructose step. More on the extraction later.
Indigo compounds in plants
I'm not familiar with the plant you mention, so I don't know if it's as good as the indigo plant, Persicaria Tinctoria. I think you should still try, as crushing the leaves shows blues thing is very engouraging. I bet you'd at least get nice greens or greenish yellows if not even turquoise or blue!
Indigo is a category of many dye chemicals, and P. Tinctoria contains (among others) indirubin, which is the red indigoid chemical that makes indigo a more dark purple kind of blue. We have another plant, Isatis Tinctoria (common name woad, morsinko in Finnish), growing here, and it's also cultivated for indigo, but it doesn't have indirubin, hence the colour it gives is a bit cooler blue. So be aware that the shades you get might be different from what you're used to seeing as indigo! Also with our I. Tinctoria I remember reading that it's recommended to pick the leaves when they're young and keep them intact for best dyeing results. Though it depends on the method.
Indigo as a compound is not water-soluble, so that's why we need to reduce = remove the oxygen from the dye bath, so that it can turn into its precursor, that is water-soluble. The precursors are sensitive to light and oxygen during the process, so it can be tricky to get it to work. In the dye process the precursor sticks to the fibers, makes it green, and when it oxidizes in the air, it turns to indigo = blue.
Also in some traditions the leaves have been fermented first, and then used in the dye vat – that might be interesting to look into! Fermentation is also a way to reduce a vat, as the yeast and bacteria use up the oxygen in the fermentation process. Here's some reading on the traditional dyeing methods with I. Tinctoria that Outi, a natural dyer from Finland, recommended:
"A treatise on the culture, preparation, history, and analysis of pastel, or woad : the different methods of extracting the coloring matter, and the manner of using it, and indigo, in dyeing" (Lasteyrie, Dearborn 1816)
"The woad plant and its dye" (Hurry 1930)
I don't have any personal experience about this, but I'm going off of this finnish blog post on dyeing with I. Tinctoria, that I think should work very similarly. Her reasoning was that high heat and oxygen destroy the precursors of indigo, but high heat breaks the cells of the plants to allow for the dye compounds to dissolve into the water, so she put the plant leaves into boiling water and then put cold water on top soon to drop the temperature to around 50⁰C. (Also with the same reasoning, if you need to rinse the plants, use cold water). The leaves turned yellow in the 20 minutes they brewed, after that her steps were:
Add soda ash (50 grams, vat pH now 11)
Whisk for 20 minutes to add oxygen (at this step it should be more blueish, keep whisking until the bubbles turn pale, though hers was green) (I'm not convinced if this step is good)
Add 40 grams of a stain remover that contains sodium dithionate to reduce and leave for an hour
Peel the metallic surface and dye!
Wow, that was long. I find indigo dyeing super fascinating so it was fun to research it again! I hope some of this is useful to you!
