Dyeing with dried indigo leaves

Because we had such a long hot summer in the UK last year my homegrown Japanese indigo lasted well into the autumn, and I didn’t have time to use all the fresh leaves for dyeing.

I’m always reluctant to waste anything so at the end of the season I cut the remaining stems, tied them into bunches, and hung them in my airing cupboard to dry out. Quite a few of them had flowers on, so I snipped these off and dried them separately in a paper bag to save the seeds.

bundles of indigo leaves

Within a few weeks the leaves had dried out and gone slightly blue (dried bunch on the right).

dried indigo leaves

I stripped all the dried leaves off and stored them, hoping to find a method of making an indigo vat with dried leaves.

I then managed to acquire a copy of John Marshall’s excellent book Singing the Blues, which contains lots of ideas for using fresh indigo leaves, as well as a method of making a vat with dried leaves. Eureka!

John’s method involves heating the leaves with soda ash (alkali) and thiox (thiorea dioxide – reducing agent), but I didn’t really like the idea of heating thiox, which produces harmful vapours above 40ºC. So I decided to try making the vat with lime as the alkali and fructose as the reducing agent. This is how I make organic indigo vats, following Michel Garcia’s 123 recipe (1 part indigo, 2 parts lime, 3 parts fructose).

The problem, of course, is that I had no idea about the quantity of indigo contained in the leaves. It was at the end of the season, and some of the plants had flowered, so the level of indigo was likely to be low. When I extracted indigo from fresh leaves earlier last year, I obtained 4g of solid pigment from 215g of fresh leaves – but I don’t know how pure the indigo was.

dried indigo leaves in pot

Fresh leaves weigh more than dried leaves so I decided to assume 4g of indigo in my dried leaves, which was probably on the optimistic side!

Here’s what I did:

  • I simmered my 104g of dried leaves in 5 litres of water for 20 minutes to remove impurities, strained the leaves and discarded the liquid.

dried indigo leaves in water

  • I simmered the same leaves in another 5 litres of water with 8g of lime and 12g of fructose for 20 minutes. John Marshall says a dark blue film should form on the surface, but I didn’t see this. The liquid was a very dark yellow. I strained it and kept the liquid anyway.

straining dried indigo

  • I then repeated the previous step three times. The second time I got a little blue, but by the third and fourth times there was significantly more blue and even a little indigo “flower”.

  • I combined the second, third and fourth extractions and decided to discard the first extraction, as it didn’t look as if it contained much indigo.
  • I let the extractions cool down and then added a couple of pieces of cotton – one plain, one with shibori bindings. I left them for five minutes, wrung them out and hung them to oxidise.
  • There was barely any colour at all after the first dip, so I repeated this three more times. The final result is shown below. The colour in the photos actually looks a bit darker than in real life.

shibori in dried indigo leaves vat shibori in dried indigo leaves vat

So the technique does work. The pale colour is probably due to low indigo levels in the leaves at the end of the season.

It is quite time consuming, but may be a way of preserving indigo leaves for later use if you don’t have time to use them fresh or don’t have facilities for composting.

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A week of indigo

It was definitely a blue fingernail week last week! It started with a couple of days in Hove with a wonderful group of textile friends who try to get together every couple of months to do a little felting or stitching.

This time, Barbara was rash enough to offer her garden to do some indigo dyeing – though some parts (usually featuring pale limestone!) were definitely out of bounds to people carrying dripping blue fabric. 🙂 The weather was glorious – the last two days of our prolonged heatwave – and the food and drink was plentiful and excellent. Barbara even baked a belated birthday cake for Carol, my partner in Women of the Cloth.

In between the eating, drinking and laughter we even found some time for dyeing, and everyone produced some great work.

When I got back home, it was time to filter my second indigo extraction from my homegrown indigo, which I’d fermented and left to settle while I was away. This produced another 4g of indigo.

Then on Friday I harvested 75g of indigo leaves, blended them with iced water till it was bright green and strained it through silk.

I used this to dye two silk scarves, one plain and one ecoprinted. Interestingly, some of the leaf prints seemed to resist the dye, while others changed colour as they were overdyed.

Also interestingly, the silk I used to strain the vegetation shows a range of colours, from the expected turquoise, through pale green to red from indirubin.

All natural indigo contains indigotin, the blue pigment, and indirubin, a red pigment – the indirubin is usually hidden by the indigotin, but shows up once the indigotin is exhausted.  Fascinating to see it separated out here!

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! 🙂

More homegrown indigo

I’ve now got a good crop of flowers on my Japanese indigo, but before they all started developing I did another harvest of the leaves – almost 200g in all.

fresh indigo leaves

Unlike last time, I didn’t do any aqualeaf indigo, as I wanted to see if I could get a stronger colour with the reduced indigo, so I needed every leaf I could get! 🙂

This time I overdyed a linen top that I had previously ecoprinted with peony leaves. It felt a little too minimal, so I thought that a pale indigo background might lift it a bit.

ecoprint linen top white

I dipped the top three times, leaving it to oxidise in between. The result was slightly darker than last time, but still quite pale and delicate.

indigo dyed ecoprint linen top

I’m drying the flowers to get seed for next year’s crop, but I’m also going to see if any of the plants survive the winter in my London garden. They are still growing – but it has been a very mild autumn so far. I’ll have to see what happens when the frosts arrive!