I would like to share with you a technique I was taught by Michel Garcia in 2017 of extracting pigment from indigo. Firstly, I have to admit that part of this technique was prompted by the farmer who gifted me the indigo as a guide as to get started. In Michel’s instructions I was using dried leaf of Indigofera which is the variety that grows abundantly in warmer climates and looks more like a shrub than a delicate annual. He did direct me as to using fresh leaf of Woad or Persicaria but I obtained so much that I had to make 3 -10 gallon extractions and I thought maybe his method was for smaller batches. None the less the big difference in fresh leaf Persicaria vs dry Indigofera is the temperature of the water and the length it needs to soak.
I tried several methods……
First I started a batch with cold water and waited about 4 days till it looked changed. This change is simply the color changing in the water from clear to greenish. If you wait long enough it will have the copper glaze such as in a proper vat. The leaves will be fermenting and you will also noticed bubbles.
Batch two I started with warm water at about 120 F and it took about 24 hours to look the same as the first batch.
In reality if you soak in the warm water it should only need about 5-8 hours before it is ready it start extraction. Fermentation is not necessary.
After I strained the liquid of the leaves and stems I was ready to aerate. I do this for a few minutes because this process will begin to separate the molecules and they will be then ready for the accelerator, which I use Calcium Hydroxide. This is often referred to as limewater. This introduction is called flocculation. It is a process of aggregation of particles to separate and coagulate. This will be the key in gathering the pigment we desire.
I have a water pump that does this for me but any kind of blender or mixer will work. If you are doing this in a small scale you can totally do this by pouring the liquid from one vessel to the next over and over….. I ran my pump for about 15 minutes and it was ready. You will notice that the water changes color as soon as you add the limewater and the ph should raise to about 10. As you mix, it will change from green to blue and eventually the blue will stop frothing abundantly and you will be ready for the next step.
At this point I am ready to strain. There are two ways this can be done. Either you wait over night and let the pigment settle as it will naturally and decant the liquid from the top carefully. Or you can begin to pour the liquid into a strainer and slowly let it work its magic.
I use a strainer that is lined with a tightly woven cotton cloth to catch all the pigment the first time. You want the strained liquid to be a yellowish color. This indicates that the pigment is all in your cloth. If the water is still green/ blue then you can re strain it to catch every particle. This is a long process and I found with my large buckets that by morning what was left was settled and I removed the liquid so had less to run through the strainer.
After you have strained everything you will want to run fresh water over the goop one or two times to make sure you clean off all particles from the accelerator.
I have collected this pasty goop that is pure pigment! At this point I can use this to create vats or for printing. Likewise, I can spread out and dry pigment for later use. I have decided to save a little for printing and dry the rest. When I create a vat I like to measure the ingredients by weight so since everything else is dry I want the pigment dry too.
For this batch there was 30 gallons of water filled with fresh leaves that transformed into 65 grams of dried pigment. I saved about 2 cups of wet for later so perhaps that would have added 20 grams dried?
Also interesting to note that the dried pigment is kind of green but when consulted with Michel he assured me that I will still get a beautiful blue from my vats. So now the next step is to try out this fresh pigment…..That will happen in the next few weeks.
I hope you have a chance to try this technique yourself.