Blue magic

Mmmm… the blue magic of indigo seems to be my theme for this summer. This week I have tried a fermentation method to extract indigo pigment from fresh Japanese indigo Koyoko leaves.

The cold water fermentation method is described in one of Liz Spencer’s (the Dogwood Dyer) online courses. I liked the slow and unhurried pace of the method and decided to give it a go. After all, I’m totally new at this and have no idea what I am doing really. The chemistry of indigo dyeing seems quite daunting, but I am equally intrigued by the variety of techniques and range of colours I can get from my sweet little plants.


When I started an in-person class in indigo growing and extraction here in Stockholm in April we got seeds for European woad, Chinese woad and Japanese indigo Maruba. We also got a pot with a few plants of Japanese indigo Koyoko. These take some time to grow and flower very late in the season, so to be able to harvest the Koyoko seeds, our instructor Katja provided us with baby plants instead of seeds.

All my Japanese indigo plants have grown very nicely and I giggle with joy and excitement every time I see them. Since I don’t have that many Koyoko plants I wanted to do something special with them. When I saw the cold fermentation method in Liz Spencer’s online class I knew I wanted to try it with my Koyoko plants.


For the extraction I picked most of my Koyoko plants for the extraction. I saved a few plants to flower so I can get the seeds for next season. I do love the brightness in the colour that I have managed to get so far with this variety.

Sunday morning was the day to start. I picked my plants and prepared a pot outside our front door, just next to the container where the rest of the plants grow. I checked the fermentation pot twice daily to keep an eye on the process. Liz lives and dyes in southern California, so the temperatures there are a lot higher than here in Stockholm, where it also has been unusually cold and rainy during the past week.

Alkalizing and oxidizing

On the fourth day I didn’t want to wait any longer – there is a risk of over fermenting. Liz lists different signs that the fermentation is at its peak and I decided it was time to stop the fermentation. I removed the indigo leaves and alkalized the mermaidy turquoise fluid. I felt very grown up when I checked the pH with a few pH strips. When I had the right pH I oxidized by pouring it between large buckets for a while.

The colour was amazing. So much blue from my little plants. I left the blue magic to rest over night and allow the indigo pigment to sink.

More dye!

Meanwhile I did a salt rub with the leaves from the fermentation that were still fresh looking. There was still indigo left in them and I got some more shades in my collection of indigo dyed handspun silk collection. I tried to squeeze some indirubin out too, but failed – all I got was green that I suspect is chlorophyll only.

Salt rub dye from the fermentation leaves that were still fresh. Soy treated antique cotton, linen and linen buttons to the left, handspun silk to the right. The right silk yarn is overdyed after a previous experiment.

And I wait

This is where I wanted to write about watching the pigment sink to the bottom and then decanting the fluid to get access to the blue magic. But I can’t, not yet anyway. The morning after I had oxidized, the fluid looked exactly the same as the day before. Beautifully blue, but not a sign of any pigment sinking to the bottom of the pot.

I got nervous and described my predicament in a Facebook forum for indigo pigment extraction methods and got some reassuring replies with encouragement to give it a few days, perhaps even a week. So I wait, while at the same giddily planning upcoming blue adventures.

Happy spinning!

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4 Replies to “Blue magic”

  1. Josefin,
    I will never be nor become as patient as you. So I live vicariously through your descriptive effort.
    You, in the living and doing. Me, in the seeing and imagining !
    Thank you from the bottom of my thirsty heart.
    Lincoln Plantation, Maine USA

  2. Hello from France ! I look forward to try to grow a little indigo and woad too next year in my garden and your articles are very inspiring. Thank you very sharing your process with us Josefin !

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