Woad

In the Spring of 2016 I grew woad plantlets from seed and when they were big enough I planted them out on my allotment. Woad is a biennial: in the first year it produces leaves and in the second it grows tall, with small yellow flowers which turn into flat black seeds. The plants then die back and readily self-seed so that the 2-year cycle begins again.

I wanted to dye with my woad and I had read that the best part of the plant to use for this was the first years’ leaf growth. However, in 2016 my plants were still very small and it seemed cruel to deprive them of the few leaves that they had produced. I waited until this year, after the plants had self-seeded and produced vigorous leaf growth. Over the August Bank Holiday weekend I cut a basket of leaves and took them home to make a dye bath.

Overnight I had soaked in a bucket of water, a metre of organic calico, cut into 2 pieces and a piece of recycled fine linen. I had scoured the fabrics (washed them at 60 degrees in a washing machine) but not mordanted them. A mordant is not necessary when dyeing with woad or indigo.

To make my dye bath I used the Fresh Woad Vat recipe from Indigo-cultivate, dye, create by Neumuller and Luhanko (see previous post for details of this book). First, with a pair of scissors, I cut the woad leaves into small pieces and put them in a stainless steel bucket. Then I poured enough boiling water over them to cover them and left them to stand for 40 minutes, by which time the liquid had turned a dark red/brown. I strained the bucket to remove the leaves (later taken down to the allotment compost heap).

The next step is to make the liquid alkaline and raise the pH of the liquid to between 9 and 10. This is done by adding small amounts of sodium carbonate (aka soda ash), stirring and checking the pH with indicator paper until it measures 9-10 and the liquid turns green. The recipe then instructed me to pour the liquid from one container to another several times to introduce oxygen into it and the liquid should turn blue. Although I tipped my liquid from bucket to saucepan about 30 times, it remained a dark green colour although I did detect traces of blue in the froth on the top. I decided that enough was enough and moved onto the next stage.

Using a large stainless steel saucepan, I added enough extra water to my dye bath to accommodate my fabric. (I had decided to only dip one piece of fabric at a time, but the fabric does need enough liquid to spread out in. The total volume of dye bath + extra water in my pan was 9 litres). Before introducing the fibres to be dyed, the vat was heated to 55-60 degrees C. I used a jam thermometer to check the temperature.* It was then removed from the heat. It is important to remove oxygen from the dye vat now. The recipe recommended sprinkling 5gm of sodium hydrosulphite** per litre of liquid over the surface and stirring carefully. I weighed out 45gm of this chemical and added it, taking great care to agitate the liquid as little as possible, and thus avoid adding back in the oxygen I was trying to remove. The dye bath was then left to stand for 30 minutes, by which time it had turned yellow.

The dye bath was now ready to use. With woad, as with indigo, the damp, wrung-out fibres are introduced to the dye bath carefully to avoid adding back in any oxygen and the liquid is agitated as little as possible. The fibres were left in for an initial 15 minutes and then carefully removed, making sure that as few drips as possible break the surface of the dye bath and using another vessel to squeeze the excess liquid into. Miraculously, when the fibres are first removed they are yellow, but as soon as the air gets to them they begin to turn blue. They were allowed 15 minutes in the air for this to happen fully, and then redipped for a further 5 minutes and the airing process repeated. With woad, as with indigo, multiple dipping is recommended in order to build up the depth of the colour but every dipping after the first should only be for a few minutes. I dipped each of my three pieces of fabric separately, first for 15 minutes then for 4 further dips of 5 minutes each. What a joy it was to see the colour appear and increase. There is something wonderful about the blueness that can be obtained from this ancient plant, with a bit of effort.

*All the equipment and utensils that you use in dyeing should only be used for that purpose and never used for culinary or other purposes again.

**Chemicals can be harmful and should be treated with the greatest care. Always check the recommendations for their safe use and wear rubber gloves and also a mask if you have any respiratory concerns.

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