Extracting indigo from homegrown plants

A couple of years ago I grew Japanese indigo in my London garden for the first time, and tried dyeing with fresh leaves as well as making a reduced vat.

This year I planted more Japanese indigo – I got the seeds from Ashley Walker of Nature’s Rainbow at the natural dyeing workshop I did in January. He said that there were two variations – broad leaved and narrow leaved, and that he had found that the broad leaved variety contained more pigment. So I planted them in two separate patches, and thanks to the wet spring and summer heatwave they have grown really strongly.

I’d read about extracting pigment by drying and composting the leaves, but this seemed to be quite a large scale process – I got the impression that I would need several years’ worth of leaves before this became worthwhile! But then I joined a Facebook group on indigo pigment extraction methods, whose admin Brittany Boles published a description of aqueous alkali precipitation extraction and also linked to a detailed account of the process by Fibershed.

So last week as our heatwave reached its peak I took the plunge and had a go at fermenting some of my homegrown indigo.

indigo harvest

I cut about half the broad leaved plants down to 7-8 inches and stripped off the leaves, ending up with 215g. I covered them with bottled water (chlorinated water is a no no and there wasn’t much rainwater around!) and kept the leaves submerged with a couple of stones.

indigo fermentation start

A couple of days later I could see an oily slick on top of the water – a good sign that fermentation was happening.

indigo fermentation middle

Then only a couple of hours later the water had turned bright green and there was a characteristic fruity smell – bingo! I decided to remove the leaves, because if you leave them for too long the yield of indigo pigment apparently drops drastically.

indigo fermentation end

I added lime (calcium hydroxide) to reach pH 10 and then whisked…and whisked…and whisked until the liquid was a deep indigo blue.

Because I’d used a dark grey bucket, I decanted a bit into a clear jar so I could get an idea of how the pigment was settling. Two days later I could see a dark blue line at the bottom of the container where the indigo had settled.

indigo precipitation

So I decanted most of the liquid from the bucket, adding it to my current indigo vat.

indigo decanting

Then I poured the sludge at the bottom into a coffee filter.

indigo filtering

After filtering and drying, I was left with 4g of homegrown indigo.

indigo pigment

I also saved the stripped stalks of indigo and stuck them in a jar of water. One week later they have developed new roots – ready to replant for the next round!

indigo rooting

I don’t know how pure the pigment is – apparently this method produces fairly low grade indigo, with bits of leaf and other impurities. But it’s a great feeling to have grown and extracted my own indigo pigment! 🙂

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Flextiles

Flextiles uses shibori, ecoprinting and felting to create original, one-off upcycled pieces. Extending the life of a garment by an extra nine months reduces its environmental impact by 20-30%.

10 thoughts on “Extracting indigo from homegrown plants”

  1. Thanks for a fascinating piece – that must have been such a great feeling. Look forward to seeing what you dye with it.

    1. Thanks Pam. I might just about have enough to dye a handkerchief at the moment – think I’ll have to process some more before I can dye with it! 🙂

    1. Thanks Ruth! It’s not really a difficult process (apart from the whisking!) – just a lot of waiting around for things to happen. I think the heatwave sped things up a bit!

  2. Thank you for this interesting info – it will be added to my two lovely books on indigo. I just love the colour, but as I already have a ‘saintly’ husband putting up with endless creative clutter, I don’t think I could inflict all this on him too. I look forward to seeing what you do with the dye.

    1. You should give it a go Antje! My references to my Ever Supportive Partner were slightly sarcastic to begin with. 😉 But he was really interested in the indigo extraction process!

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