I grew Japanese indigo Persicaria tintoria in 2019 and while I did a bit of fresh leaf ice blender dyeing (mainly to reassure myself that there was indeed indigo in the leaves) during summer, time got away from me and most of the harvest was simply dried for later.
Here is my seed starting set up. The top row is all indigo.
Precious baby indigo seedlings.
I harvested several times over the season, with the majority right as it was starting to flower. For drying, I just bundled it and hung it. For a while, it took over my studio and the back screened porch. Once dry, I stripped the leaves off the stems and stored in bags.
I decided to make a chemical reduction vat and from there extract the pigment for making indigo wood stain paint.
I followed the dried leaf indigo recipe from John Marshall.
After heating 50 grams of dried leaves in water, the water started turning brownish, which I drained out, added fresh water and began to cook down with the thiox and washing soda. Since my end goal is not to dye with the vat but to extract the pigment out of the leaves, I tried to keep the water level on the low side, just enough to barely cover the leaves.
Soon, the "oil slick" thing started appearing on the surface, which is reassuring. It is working!
Then I strained the leaves.
First, I poured it back and forth between two pots.
You can see the deep blue foam.
I did this for what felt like forever (ten minutes) and finally grabbed my hand crank beaters.
After about five more minutes, the foam started turning green and pale. In the end, I aerated the indigo bath for 35 minutes.
To be sure it was done, I dipped another piece of wool yarn in there. No color on the yarn at all!
Above left is the test yarn when the vat was ready to dye and on the right is the test yarn after aerating, which means all of the pigment has been precipitated.
Next I poured the bath in a mason jar to settle. The pigment settled to the bottom of the jar.
It took 48 hours to fully settle, at which point I poured off the top liquid until only the sludge remained and then poured it through a silk scarf to filter it. At this point, I also poured a little warm water through it.
Once it was fully dry, it cracked and flaked off the silk fabric easily and I put it in my mortar and pestle to grind into a fine powder for making paint.
Below photo is a second batch that yielded a deeper color, which I think was a combination of cooking the leaves longer before discarding the yellow water and this particular batch of dried leaves were picked later in the season so perhaps had a higher indigo content.
Each time I do this the results are ever so slightly different and I have just barely scratched the surface of my dried leaf stash. Next, I plan to experiment with extracting dried leaf pigment from other types of indigo vats.
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