Extracting Pigment from Japanese Indigo Leaves

Japanese indigo in flower after many cuttings have been taken

Japanese indigo in flower after many cuttings have been taken

I’d like to share with you my experiments with extracting indigo pigment from fresh leaves. I dried most of my leaves so I didn’t have a lot to work with. My results are not conclusive, I still need to work on my method to get it down, but it is an interesting process.

I would like to use my homegrown indigo without a chemical reducing agent (hydrosulfite). Processing Japanese indigo by the traditional composting method requires a lot of volume and will not work for someone with a small crop. Instead I am extracting indigo pigment from my plants. The pigment can then be used in any indigo recipe.

The first step is to soak the fresh leaves in warm water. I tried this in various ways, for a couple hours, overnight, and for a couple days. I think next time I will try letting them ferment for a while. They released a brownish yellow color into the water with a little sheen on top.

Indigo processing soaked leaves

Next, I strained out the liquid by dumping the leaves into a bucket lined with a nylon mesh bag from a paint supply store. These bags work great, BTW! I squeezed as much juice as I could from the bag. When you squeeze the leaves a gray blue liquid comes out. There is still a lot of indigo in these leaves so I returned them to soak and extract a second time.

Soaked indigo leaves are strained though a colander and nylon mesh bag

Soaked indigo leaves are strained though a nylon mesh bag

The next step is to aerate the indigo juice. I started by pouring the liquid back and forth between two buckets 20 times.  I added calx water (mix the lime with water, let stand, use the clear liquid) and added enough to get the ph up to 9. For some of my attempts it was a little higher, more like ph 10. When the calx water mixes with the indigo liquid, it turns greenish.

Just pouring it between the buckets to oxidize has not worked for me. I have to whip more air into the indigo juice. I have tried using a blender and a stick blender, but have settled on using an electric mixer and beating it for 15 minutes. Whew!

Using a hand held mixer to aerate the indigo liquid

Using a hand held mixer to aerate the indigo liquid

I am always hoping the mixture will turn blue, as it did in Michel Garcia‘s workshop using dried indigofera leaves.  But instead it is mostly olive greenish with a little blue around the edges. When I am done mixing, I put it in large glass jars out of the light to settle out for a couple days or more, up to a couple weeks.

Indigo pigment settling out

Indigo pigment settling out

Indigo processing pigment settles

The pigment is settled at the bottom of the jar.

When the pigment has settled, I pour it into a colander lined with a cotton cloth.  I have not found it necessary to decant the mixture, as Jenny Dean suggests. When the indigo particles are really ready they will sit on the cloth and yellow liquid will drain into the bucket. If the liquid that drains out is greenish, there is indigo that still has not separated…I would put it back into the jar to settle some more.  The idea is to separate the pigment, which is blue, from the yellow liquid.

Indigo pigment separated from liquid by draining in cotton cloth

Indigo pigments separated from liquid by draining in cotton cloth, note that one is green and one is blue.

Here is where I am having difficulty. Sometimes the pigment that separates is blue, but frequently it is green. I have tried putting it back into a jar to settle more, sometimes that helps, sometimes not. Do I need to beat it longer?  Add more alkali?  Soak the leaves longer? If anyone has any suggestions I’d like to hear them. I plan to keep working on this with next year’s crop of leaves to get more consistent results.  I believe that even if the pigment is greenish, it will still reduce in an indigo vat.

Organic indigo vats made with fruits, sugars, and other natural substances.

Organic indigo vats made with fruits, sugars, and other natural substances

After the pigment is collected in the cloth, it can be used as a paste, or dried and ground to a powder. Then it can be used in any indigo recipe.  I have been working with the organic indigo recipes developed by Michel Garcia.  It’s amazing that something as ancient as this blue dye still has mysteries left for us to discover.

Be inspired by the mystery!                                                                                                          ♥Linda

6 thoughts on “Extracting Pigment from Japanese Indigo Leaves

  1. Thanks so much for sharing your experiences with this method, Linda. What a great post and inspiration. I will be planting much more Indigo this spring! Seems amazing how fickle Indigo can be…..

  2. Thank you for sharing your experiments with us, Linda. You have given me some good ideas. Over the last several years I have tried with varying success to extract indigo pigment. I was hoping to extract it without adding lime or increasing the pH, so it would be really pure. This seems to be more time and labor-intensive than it is worth, I’m afraid. All my information has come from trial and error based on what I have read online and in books. I would love to put some of our findings together, if you are interested. I grow quite a bit of indigo, but am not very organized with documenting my experiments.
    One thing I wondered is how you adapt the recipes for a natural vat to your wet paste. The ones I have seen are always for dried.
    This year I also tried using the fresh extract liquid to make a natural vat. I almost got it to work, but between my lack of experience and not being consistently home, it failed and I gave up and used Rit Color Remover to make it work.
    Concerning the different colored pigment – Was the pigment extracted from the same harvest? I have found that later in the year my blues are not as vibrant, and also when I double-soak the leaves. I wonder if there is more contamination at that time, from the indigo red or something.

    • Hi Nancy, thank you for the comment. Adding the lime water instead of the powdered lime is supposed to keep lime particles out of the indigo. Since alkali is always used for reduction, having a little alkali in the indigo does not concern me too much. There’s also a technique I learned from Michel, “washing” the pigment…when the pigment is separated and in the cotton cloth I use a squirt bottle and wash down all the indigo particles that are stuck to the sides of the cloth, to collect them at the bottom. The water cleans impurities out of the pigment and drips down into the bucket.
      Somewhere in my notes I have Michel’s suggestion for how much paste equals how much dried, but so far I have dried my pigment. It is not hard to do and it keeps well that way. If you want me to look it up send me an email (linda@lindahartshorn.com), it would be good for us to correspond.
      All the experiments I did extracting pigment were done over a couple weeks with small amounts of indigo leaves picked rather late in the year, not at an optimum time. I dried most of my crop as I left home to go to Michel’s workshop during what would have been a very good time to try these methods.
      It is interesting that the Japanese have a very specific method for processing this plant and I sometimes wonder if the indigofera species would be easier to work with. I have never grown it and don’t know if it grows here, but it might be worth a try.
      Thank you for sharing your experience, and I look forward to hearing more from you!

  3. Fresh method: Did it years ago. Liked the color as more aqua and not blue/blue. Would like to get in touch with you. Also if you are near Portland OR the exhibit at the Museum of Contemporary Craft is awesome. Rowland Ricketts. He will be giving a lecture in April.

    • Hello Ladella, thank you for your message. I like the aqua color as well. I live near Eureka in northern California and get up to Portland once a year or so…would love to hear Rowland Ricketts speak. I will send you an email.

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