(Other names of this plant are Persicaria Tinctoria, formally Polgonum Tinctoria, also called Dyer's Knotweed).
There were less leaves in the jar and I left it for 9 days (instead of 7) because I was busy with other things. The yellow colour of the liquid around the leaves seemed more soupy than before. It had stood in our kitchen, which was generally around 20 degrees centigrade. I took the jar as before and heated slowly in a bain marie to 68 degrees centigrade, after an hour I took it off the heat and let it cool a bit before draining off the liquid.
When this was done the leaves time were a slimy mush. Last time I used this dyestuff I had not left the leaves soaking so long beforehand and the residue at this stage was more like over cooked spinach, this time they were more like something out of a stagnent pond. That's what they smelt like too!
This method produced a much greater quantity of blue dye, even though there were less leaves. In the photograph below you can see the results of my first dyeing session on the right (100g wool, approx 30g silk) the yarns on the left (200g wool) were dyed from the second jar of leaves.
I think that maybe the last Japanese Indigo session this year. However, I may have enough woad to give that a go (about 5 plants have survived inspite of the greedy slugs) and I have a purchased sachet of "natural indigo" to try out.
I'll be letting my plants regrow now, and expect them to flower in October / November and then produce seed for next year. I have 3 plants that I did not cut back flowering on a windowsill in the house already. I'm told that keeping seed of at least 3 plants is important to ensure genetic diversity in the seed.
Just a note about indigo in general - Persicaria tinctoria (originally from Vietnam and south China,long used in Japan and China) is just one of a large number of plants that yield indigo. Others popularly used for dyeing include:
Isatis tinctoria, the European plant "woad" called "pastel" in french);
- Isatis indigotica - a relative of woad found in China;
- Indigofera arrecta, originally from east Africa, also grown in Indonesia and the Phillipines;
- Indigofera cerulea from north west India;
- Indigofera tinctoria, from tropical Asia, probably originally India;
- Indigofera suffruticosa, used in ancient civilisations of Mexico and in Peru, later introduced to Indonesia.
For anyone who wants to learn more about this dye plant, I recommend Teresinha's Wild Colours website. She is offering seed for sale, and I'm sure she is a good source for seed as it seems to be very important that the seed is fresh. Seed I purchased from a large seed company a couple of years ago did not germinate.
A Dyer's Garden, Rita Buchanan, pub. Interweave Press, 1995, ISBN 1-883010-07-1
two pages about the Japanese Indigo (under the name Dyer's Knotweed) and how to grow it, two more pages on dyeing with indigo plants.
A Weaver's Garden, Rita Buchanan, Dover Publications, 1999, (abridged version of longer text published by Interweave Press in 1987), ISBN 0-486-40712
18 pages on Indigo, which includes chemistry, history, dye instructions, and a page and a half dedicated to Japanese Indigo (under the name Dyer's Knotweed)
A Dyer's Manual, Jill Goodwin, 2nd edition Ashmans Publications, 2003, ISBN 0-9544401-0-2
A very useful book on dyeing from plants you can grow or find in hedgerows which has a whole chapter on "Indigo" including woad and Japanese Indigo (under the alternative name, Dyer's Knotweed).
Natural Dyes: Sources, Tradition, Technology and Science, by Dominique Cardon, published in June 2007 by Archetype Publications Ltd.
The most wonderful reference book imaginable for anyone seriously interested in natural dyes, and the only book I have found that is really good on the chemistry of natural dyes.
I have the original French edition (cheaper, bought from www.Amazon.fr):
Le Monde des Teintures Naturelles, par Domonique Cardon, pub. Belin, 2003, ISBN 9-782701-126784-01.
I also have to recommend the Guild I belong to, Online Guild of Weavers Spinners and Dyers. I was given the seeds and dyeing instructions by a fellow Guild member, and several members of the Guild have been involved in a valuable discussion this summer about our experiences of growing and using the plants.
This link gathers together all my posts about Japanese Indigo (in reverse order).