Since starting on this natural dyeing adventure several years ago now, Woad dyeing was always a major goal.
There is so much history and tradition (especially in Britain) tied up with woad as a dyestuff. Economically it was an important crop for centuries, protected by restrictions on imported indigo in Elizabethan times. It contains the same chemical for producing blue as indigo, just at a lower concentration.
Woad – Isatis tinctoria, is a member of the brassica family. It is biennial, meaning that it produces a rosette of leaves in the first year, then flowers the next. It is the first year’s leaves that yield the best colour.
The extraction of dye from woad is very different from other dyestuffs. It’s not a matter of just chopping it up and boiling. Woad dyeing is a far more complex chemical process. Traditionally this involved fermentation vats (of stale urine, very stinky), and the whole business took weeks. These days a chemical process for woad dyeing is quicker, but still takes several hours.
After a bit of trial and error this method is producing nice results, but still needs perfecting.
Grow your Woad
- Woad grows easily from seed. Chiltern Seeds sells woad seed. Sow in spring or in the autumn for an earlier crop. You need a lot of leaves! most natural dyes need an equal weight of dyestuff to dry weight of yarn/fibre. You need x 4 when to comes to woad. That’s 400g of leaves for every 100g of yarn.
- Harvest when the leaves are around 6″ long. The plant will produce new growth so a few harvests are possible through the summer. Blueish tips on the leaves are a good sign. Use them as straight away.
Tip. The plants flower.in their second year. They aren’t much good for dyeing with at this stage. But leave some plants to go to seed. Collect that seed when ripe for future plants.
Prepare the leaves
- Give the leaves a rinse and break up into pieces.
- Have a big pan of water on the boil (best to get this ready as you harvest). Use rain water if possible, or soft water. The tap water here is very hard, so if there isn’t enough collected rain water I use filtered water.
- Strain the leaves and put into another large pot.
- Pour over the boiling water to cover the leaves.
- Press them down to exclude any air and leave for about 40 minutes.
- Strain the steeped leaves, squeeze out as much liquid as possible. It should be a murky yellowy brown..
- Adjust the pH. It needs to be around 9. Lots of recipes call for Soda Ash, but household ammonia works (just a few drops at a time. Check it with litmus paper..At this point it will change to a muddy green.
- Now for the ‘fun’ part. To aerate the dye and activate the dye molecules pour the dye from one pot to another, Or you can use a whisk. The idea is to get as much air in as you can. Do this for at least 10 minutes. A blue foam will start to form.
- Now the dye pot need to be deoxigenated to make the ‘blue’ dye available for dyeing. For this you need a Reducing Agent. Many recipes use Spectralite. But the active ingredient in Colour Run Remover (Sodium Dithionite) serves the same purpose.
- Sprinkle a couple of dessert spoons of this powder over the surface.
- Cover and leave undisturbed for another 40 minutes. You should see a rainbow film form on the surface and the bubbles disappear.
- Have your yarn or fibre prepared. It doesn’t require a mordant. But it doesn’t hurt if you have mordanted. But it should be clean and thoroughly soaked beforehand.
- Introduce the yarn gently and carefully. Try to disturb the dye as little as possible. Leave the yarn in there for a few minutes.
- Take the yarn out, squeezing out excess liquid as you go.
- Now the magic happens. It isn’t clear in this photo as the sun was really bright. But the dye and yarn were a vivid green at this point.
- When you pull the yarn out the woad dye oxygenates and the green (sometimes more yellow) reacts and becomes blue before your eyes.
- Leave the yarn to dry in the open air.
- Rinse out any excess dye. Wash in pH neutral detergent.