Japanese Indigo

These skeins of yarn (commercial spun, not my spinning) are all dyed with indigo from Japanese Indigo plants (Persicaria Tinctorium) grown at home, on the front room windowsill and in the greenhouse.

The yarns in the top row are a Traub worstead spun wool, in the bottom row spun flamme silk from Gaddum & Gaddum Ltd. (I intend to use these yarns in weaving scarves).

And this is what the plants look like, they are the straggly green leaved plants. The dark leaves belong to basil "Purple Ruffles" and the stoneware pot at the left side of the picture holds a Pelagonium with nutmeg scented leaves.
The seeds arrived in the post last winter from one of my friends in the Online Guild of Weavers Spinners and Dyers, along with instructions for different ways of making dyebaths and some samples from my friend's dyeing.

Following my instructions I found a large Kilner jar, filled it with leaves, covered them with water and left the jar to stand for a few days. The "few days" turned into a week, and the leaves had started to ferment. Gas bubbles pushed the leaves up the jar and it overflowed (note: next time leave a couple of inches empty at top of jar). The liquid at the bottom of the jar looked yellow, and it began to smell like rotting brassicas (i.e. cabbage, another plant in the brassica family).

Even before the dyeing process was begun, it was clear that these leaves contained blue pigment, see what has happened where this leaf is damaged...


Before the dyeing session I also had to prepare the yarns. The wool came in an 100g skein, from which I wound smaller skeins (not weighed, but 12 skeins of differing lengths), and the silk came on a large cone. When the skeins were wound, and loosely tied at least 5 or 6 times per skein, I put them into pans of warm water with detergent and heated them gently for about 20-30 mins. to make sure they were well scoured of any substance (especially lanolin in the wool, seracin in the silk) that might impede dye take-up. After the detergent and anything else was rinsed out, I left them in bowls of water to wait for dyeing.

The dyebath was prepared by warming the jar in a bain marie, created by resting the Kilner jar on the stainless steel basket from my pressure cooker, turned upside down in a 20 litre stainless steel dye bucket.

The instructions said to raise the temperature slowly to 71 degrees centigrade. I actually stopped heating it at 68 degrees. Then, I stained the liquid from the leaves with a nylon sieve that I reserve for dyeing use, poured the liquid into my bucket, and whisked for 20 mins with a slotted stainless steel spoon. At the end of this time the bubbles looked blue.

Why whisk? To introduce air into the liquid and oxidise it (i.e. introduce oxygen). There's a good article about using Indigo in Shibori dyeing in the latest Journal. Author Jane Callender explains how the oxidisation causes two indoxyl molecules (which are unstable) to combine and form the blue pigment indigotin.

The next stage was to add an alkali liquid to the dyebath to adjust the pH level. I was going to use "washing soda", but my dyeing instructions did not tell me how to make the liquid.

I recalled that I have a little booklet from Helen Melvin: "The Colour of Sea & Sky: The Art of Dyeing Indigo". I ran to find it, confident that she would have explained this - and there it was, p.9. 4 tablespoons Soda Ash into a litre of very hot water. Thank you Helen! It was like having a friend on hand when I needed you.

The dyebath was returned to the electric hob and warmed up to 50 degrees, and then half a spoon of "spectralite" sprinkled on the surface. This is a reducing agent (reduction is the removal of oxygen). Jane Callender says " a reducing agent... removes or 'digests' some oxygen from the indigo [and] causes it to change to leuco-indigo". The change is visible to the eye, as the dyebath gains a yellow tone, which took my dyebath from very blue to a deep moss green. Good! Just as my instructions said it should... so, time to add a couple of small wet skeins, and leave them 10-15 mins for the dyebath liquid to penetrate. Helen makes the point that leaving material in an indigo dyebath longer does not give a deeper colour. Deeper colours are produced by re-dipping... I remember reading about this before in Jenny Balfour Paul's book "Indigo" which is a wide ranging account of the historical and worldwide traditions of indigo dyeing.


After several skeins had been dyed, the reduced bath became more yellow, and this very yellow looking bath below was the one that actually gave the deepest shades of blue.

I used almost all the bowls and buckets I could find. I had one bowl with wet skeins of wool ready to dye, another with wet silk ready to dye. I had a bowl to rest my sieve on to put yarn in when it was immediately out of the dyebath...

oh, better interupt here. When the yarn is lifted out of a dyebath, like that one pictured above, it looks yellow. The blue colour forms as the pigment oxidises - or takes up oxygen from the air. Magic to watch!

...back to buckets etc, see below, a bowl to rinse the yarn after it has oxidised and turned blue, then a bucket to soak it a while in a strong saline (salt water) solution. A bowl to leave the saline soaked yarns until I get a moment to rinse them. The rinse and the soak in saline are essential to remove excess pigment and fix the colour so it won't rub off the yarn later.

It was all great fun and I was happily "singing the blues" to myself throughout this wonderful dye session.

References:
(article)Indigo and the Tightening Thread, Jane Callender, in The Journal for Weavers, Spinners and Dyers, 231, Autumn 2009;
The Colour of Sea & Sky: The Art of Indigo Dyeing, Helen Melvin, copyright 2007, self-published;
Indigo, Jenny Balfour Paul, 2nd edition pub. Archetype Publications Ltd. 2006, ISBN 1-904982-15-8