When it works, woad dyeing is fantastical. However, it has happened that after a long morning of processing a dye bath, I have sat there with a cup of tea, staring at a greyish bit of wool, willing it to change colour. Eventually, the tea has grown cold and I have had to be led away, a walking shadow. Magical thinking is not enough, even Macbeth's witches had to get the recipe right.
Unfortunately, not only are there several distinct methods of making a woad dye bath, all sets of instructions for the phases of any single method differ in basics like timings and quantities. Confusion now hath made his masterpiece. On Bank Holiday Monday, it was a great relief to discover my notes from last year, still on the shelf. What follows is my version of the chemical method. It is a pared down, simplest and quickest possible amalgam of all that I have read.
Step one is to prepare the wool or fabric or anything else you want to dye. No mordant is needed, but the material has to be thoroughly wetted - preferably soaked overnight. I had a skein of white Jacob fleece I had spun, which weighed 70g and was about 200m long. I made it into a long loop and secured it with loose cotton ties at four points.
Next, cut your woad leaves. Best to do it in the morning, because this is going to take best part of the day. They can't be kept in the freezer until you have a bigger collection. However few fresh leaves you have, be bloody, bold and resolute - go for it. The recipes call for a kilogram weight, but I have never had more than 600g at one time and last Monday, I had a magnificent haul of only 300g. While the amount of dye for a given weight of leaves is said to vary by season and plant vigour, most instructions suggest a ratio of four times the weight of leaves to the weight of wool. I was well pleased to have just over four times the weight of the 70g of wool I wanted to dye.
It is generally recommended that first year plants are sown in March and harvested in July and August. I germinated seeds late last summer and overwintered some outdoors and a few in a tub in the greenhouse. The latter have been desperately trying to flower and were clearly hating pot life. I decided to cut them down to the base and though the plants are still small, I also took the biggest leaves from the ones on the veg patch. The potted woad roots have been replanted out in the garden.
You can extract the dye and keep it long term, if you want to accumulate enough to dye a bigger weight of wool in one go. There are excellent dye extraction instructions on http://www.woad.org.uk and much more authoritative information on woad, its history, chemistry and methods of dyeing. If you don't have woad plants, you can buy powdered woad and all the other chemicals needed on this site.
Fill a 10 litre pan about half full of water and turn the heat up high to bring it up to 90 degrees centigrade. Chop or tear the leaves, rinse off the dirt and leave them to drain.
When the water is up to temperature, turn off the gas, put in the leaves and leave them for 10 minutes, with a lid on to keep the heat in. Now you need to cool the dye fast. Have a sink full of cold water ready, put ice cubes in, if you have them. Lift the pan into the sink and stir steadily, letting the cold water all round it leach away the heat. My thin pan comes down to 50 degrees centigrade in a few minutes, but a heavier pan might be more of a challenge to cool within five minutes.
Pour the contents of the pan through the colander into a bucket and squeeze the leaves to get out as much fluid as you can. Smells of cabbage and 50 degrees is still hot, so wear rubber gloves.
Pour the brown water back from the bucket into the pan. This dye has to be alkaline. Dissolve a large teaspoon of soda ash in hot water and pour it in. The excitement begins as the dye bath darkens, a borrower of the night. Next, get an electric whisk and stand there whisking for ten minutes. My Mum was visiting and it was really nice to have her do all the hard work. The bath is supposed to get frothy, although ours didn't on Monday. You might see bits of blue on the whisk or the sides of the pan. This is woad blue, but because it is oxygenated, it won't lock on to things and is easy to wipe off. A little water clears us of this deed.
Woad blue is light fast. If you overdye it with a yellow plant dye, the wool goes green. On a school trip to the Musee Cluny, donkey's years ago, I remember admiring The Lady and the Unicorn tapestries, but wondering why they had embroidered the grass such a blueish colour. Now I know that in the centuries since it was made, the yellow plant dye that made the blue into green has faded, but the woad is still going strong.
In order to get a blue woad dye to lock on permanently, you have to deoxygenate it. Once something soaked in almost colourless, deoxygenated woad is exposed to the air, the woad oxygenates, bonding to the thing while turning blue. The chemical method for deoxygenation uses thiourea dioxide powder, also known as Spectralite, sprinkled on the surface. For this small dye bath, I used two big teaspoons full, generosity seems to pay off. Keep the pan at about 45 - 50 degrees. Double, double, toil and trouble, some say you have to keep the temperature steady for a couple of hours using a bain marie method, which means boiling the kettle over and over again. I find you don't need to wait longer than half an hour and it works just as well if you keep the temperature steady by leaving the lid on and turning on the heat low for a minute or two if it goes below 45 degrees. When the dye bath turns a translucent yellowish green, it is about ready.
Before it goes in, soak the wool in the hottest water you can get out of the tap, so it won't chill the dye bath. To avoid reoxygenating the woad by accident, DO NOT STIR. Slide the wool in and out, trying not to splash or drip. On a last minute impulse, I put in some wooden buttons too. Because I hadn't soaked them, they floated. After 10 minutes or so, pull the things out of the dye bath.
I wasn't confident I would get much colour out of these leaves, being so early in the season and so few. Who would have thought the old potted woad to have had so much blue in it? Usually, I get paler shades than this. I intended to try for a spectrum of blues, but the first dip gave such a strong blue, that dipping just the far end of the loop for another ten minutes didn't result in a much deeper colour change when I aired it again. The dye bath strength always diminishes as dye is used up, so second dips never do double the initial colour and third dips produce even paler additions of colour.
I put the whole loop in for the third dip, and there was still enough woad in there to dye the white end pale blue. A rinse in plain water and hang it up to dry.
The buttons were too dry to get much woad on board while the dye bath was strong, but I left them in during the later two dips and they slowly submerged. At the end, they had picked up a nice blue, though uneven and pale. Next time, I'll soak everything beforehand.
When the hurlyburly was done, all we had to show for it was a ball of blue wool. Good day though, and thanks for all your help, Mum.