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

Dyeing with Fresh Indigo Plants

Japanese indigoplants in my garden closeup

Japanese indigo (Polygonum tinctorium) growing in my garden

I grew indigo in my garden this year. It has been a long time since I first tried dyeing with fresh plants.  My small patch will yield enough leaves to try a few different dyeing methods.

Stripping leaves from indigo plants

Stripping leaves from indigo plants

The leaves contain the indigo dye, so they are removed from the stems. Here I have thinned out whole plants but you can also pick leaves off the living plants and let them grow back.

"Indigo smoothie"-fresh leaves blended and strained

“Indigo smoothie”-fresh leaves blended and strained

The leaves go into the blender that’s 1/3 full of cold water and a few ice cubes.  Unlike the way I usually dye with indigo, this is a cold method.  After blending I add more leaves and blend again.  The “indigo smoothie” is a beautiful green color. It is strained through a cloth and the juice is the dyebath.

Silk in fresh indigo dyebath

Silk in fresh indigo dyebath

The fiber is put into the cold dyebath. I am dyeing 30/2 silk and some wool/mohair yarn samples. There are different ways to do this, leaving the fiber in for longer or shorter or removing it periodically to oxidize.  I am following John Marshall‘s method of rotating the skein slowly for one hour. As I work I can see the color changing.

Silk skein hung to drip  and oxidize

Silk skein hung to drip and oxidize

Oxidizing, which means exposing the indigo dyed fiber to oxygen, deepens the color. I love the dark wet colors of the silk, but I know they will dry much lighter. This method yields pastel shades of blues and greens.

I have mordanted some of my fiber in alum to see what happens. I anticipate that it will be more greenish, picking up the yellow tones in the dyebath.

Silk with no  mordant, alum mordant, and mordanted silk soaked in leftover bath.

Silk with no mordant, alum mordant, and mordanted silk soaked in leftover bath.

Here are the silk skeins I dyed.  The unmordanted skein is a light blue/blue green.  With an alum mordant I got a pale mint/sage green.  Putting a mordanted skein in the leftover bath and letting it sit  for a couple days I got a light yellow green color, which doesn’t really show in this photo. These light and even colors are beautiful as is but would also be nice for overdyeing.

Fresh indigo dyeing colors on wool croppedI got more dramatic results on my wool/mohair samples.  A nice light blue on unmordanted wool and a sage green on the wool with alum mordant. I put a mordanted and unmordanted sample in the leftover bath for a few days and got this nice spring green, very similar on both samples.

So what is next?  I still have my leftover dye bath which is fermenting in a pot.  Leftover dye bath can be heated to produce yellows, or alkalized to make blue.  And I also have plants still growing in my garden.  So more dye experiments are sure to follow.

Happy dyeing!                                                                                                                         ♥ Linda

http://www.lindahartshorn.com