Japanese Indigo Plant Dyeing and Overdyeing

This week, here are my reflections on dyeing with Japanese Indigo plants, overall, very happy, as the plants have loved a hot summer in Wales. During the heat wave, they didn't mind surviving on one good watering each week and dry or damp, they never get eaten by slugs, which is such a bonus in my garden. I'd say not only have the plants grown a bit larger, but also, there has been more indigo than usual in each leaf. I can wedge about 2kg leaves and stems into my dye pot and looking at this year's results, I have had perceptibly more indigo blue out of each dye session than I have in previous, cooler damper years. 

Much as I prize the continuity of use of woad, which stretches back into prehistory, sometimes I wonder why I bother growing it. Mostly, mine has provided lunch for slugs. Half the woad plants have been munched to extinction and the remainder are looking lacey. Hopefully, they will survive to flower next May so I can save seeds and keep the stock going. 

The Japanese Indigo plants seem robust enough to take over the garden, except they always get killed off by cold weather before they can set seed. I've found their dye content diminishes as autumn sets in, so this month, I've been uprooting plants from the border, steeping pots of fresh leaves and hunting my cupboards for more things to dye blue.

Using the method on the Wild Colours website with dithionite to deoxygenate the vat, I can get fairly deep blues from the first dip and then medium blues with repeated dips, but achieving a consistent shade is beyond my powers. This is a whole kilogram of chunky yarn I dyed to knit into a jacket. You can tell the finished object is going to be as stripey as ever.

Despite repeated dips in the vat, the shades I get tend toward baby blue and I'd prefer a colour with a bit more guts. I have tried overdyeing naturally coloured wool with indigo and I think greys turn out better than browns. These skeins were millspun from white Llanwenog sheep, blended with increasing amounts of Black Welsh Mountain fleece to create the two tones of grey. Each skein was divided into four 25g portions. From the left, you can see the results of dipping the first portion of each shade while the indigo vat was moderately strong, the next three skeins were dipped when the vat had been partly used up and the next three were dipped when it had become very weak at the end of the session. The final three skeins on the far right show the original, undyed colours. The overall effect reminds me of the colours of both sea and sky - on a typically wet Welsh day. Note to self, for clothing, I think I'd like the lighter grey with an indigo overdye.

My experience of overdyeing other plant dyes with indigo has been fraught with misjudgement. Whether I dye with indigo before or after dyeing with a yellow, balancing the strength of the two colours is a bit of a nightmare, particularly given the unpredictability of the strength of fresh plant dye baths. Usually, I have too much blue and the wool ends up turquoise.

This year, I dyed some tops with a strong yellow weld dye bath (right) and then overdyed with different strengths of indigo (left, only I didn't try overdyeing any tops with that deepest blue at the top). The three shades of Lincoln Green didn't come out too bluish, but I still can't say I'm thrilled with the colour.

Comparing the overdyed Lincoln Green yarn on the left of this picture to the iron modified weld dye on the right, I think I prefer the latter. Blue adds freshness to the green, but loses warmth. And anyway, with a single dip, the dye I get is always patchy, with repeated dips, the blue gets too strong and I am back into turquoise territory.

Lately, I thought I'd try steaming an indigo dyed silk scarf with oak leaves and an iron blanket, same method as this post, only with a few of the oak leaves also dipped in a weak iron solution. It's been very blowy this week, great for collecting leaves, not so great for working outdoors in daylight. Still, the colour in this photo taken in my kitchen shows what I remember starting with, a fairly light blue, uneven indigo dye. I expected the iron from the blanket to add a grey overlay wherever it had been pressed against the silk.

When I unrolled the bundle, the oak leaves had taken up an iron halo and left a yellowish shade of their own dye, but far from darkening to grey, the indigo blue background looked much paler. Maybe the heat of steaming destroyed some of the indigo? Apart from those silhouette effects, there isn't much evidence of the iron blanket having been there.

All very interesting, there's always more to learn. I can dip the silk in another vat, if I decide the blue is too anaemic. There's still plenty of Japanese Indigo growing in the garden and no sign of cold weather yet. Plants in the greenhouse are flowering and I think the seeds are maturing early, so I may not need to take cuttings.