It really feels like a miracle, I have finally managed to create lots of lovely shades of blue from my very own home-grown woad!
You may remember my previous post about woad, when I was trying to extract blue pigment from my first woad leave harvest. When aerating my woad liquid, I never got the blue coloured froth that you are meant to get, and so I was a bit uncertain if I had done things correctly. In the end, though, I did get some blue-coloured sludge at the bottom of my container so I was cautiously optimistic but decided to wait for the second harvest of leaves before trying to dye any wool with it. I fed my woad plants with some organic fertilizer and waited for them to grow again.
Well, a few weeks ago I decided the time had come for the second harvest. This time I tried to do everything by the book and measure the temperature super-carefully with a new thermometer, so that I wouldn’t destroy any of that precious blue pigment. I shredded the leaves (which unfortunately I did not get round to weighing), poured hot water from the kettle on them, and waited for an hour. I added the very alkaline liquid and the blue sludge from my first attempt to the pot – this was enough to change the pH to 10, and it also dropped the temperature to below 50 degrees C. I whisked the liquid for a few minutes, and this time – oh joy – I soon had a nice blue froth and the colour of the liquid had changed to a very dark blue-green.
Then, to prepare the vat for dyeing, I reheated the liquid to 50 degrees, added a couple of spoonfuls of sodium hydrosulphite to remove air from the dye bath (this turns the normally water insoluble indigo pigment to a water soluble form that can be used to dye fibre). I waited for 45 minutes and by the end of it the colour of the liquid had turned to a yellowy brown colour.
Meanwhile I had prepared some Finnsheep top by tying some string to the ends. This would allow me to submerge the fibre in the vat and then pull it out using the string without introducing too much air back into the vat (which would turn the pigment back into the insoluble format). The fibre had been washed but mordanting is not necessary with indigo.
The indigo dyeing process really feels like a magic trick, particularly the first time round when you can’t quite believe your eyes. You soak the fibre in the yellowy brown liquid for some time (between 5-20 minutes), then carefully pull the wool out. The wool yellowy-green as it comes out of the vat but it turns blue within seconds. I felt like a small child, jumping with joy and laughing with excitement when I saw the magic taking place! I could hardly believe I was really managing to do this! I wish I had had a photographer with me to record the process (unfortunatelyI didn’t have enough hands to do both the dyeing and the photographing at the same time).
After dyeing, I let each length of wool top air for about 20 minutes, before putting them back in for another round, building the colour layer by layer like you are supposed to. By the time I ran out of energy, I had a few hundred grams of blue of various shades, but I had not yet exhausted the bath. The vat will last for a while, and if it turns back to blue (the insoluble form) you can revive it by heating it back to 50 degrees and adding a bit more of sodium hydrosulphite to remove air again.
I have heard that many dyers prefer Japanese indigo to woad as you get stronger blues, but I must say the woad blue is very beautiful, naturally pretty in a elegant sort of way. I did not get very dark navy blue but then I wasn’t trying to get dark shades anyway. I’m very pleased with the medium blues and the lighter shades are particularly pretty. I will try to grow Japanese indigo too next summer, but I will definitely grow more woad – it has instantly become my new favourite dye plant.