Woad – blue

While most natural dyers rely on indigo for blue dye medieval dyers would extract the same dyestuff (indigotin) from the woad plant which grew throughout Europe.

Growing woad

I grew woad before in our first house in Aranui and found it quite easy to grow so it was an obvious choice to grow in our larger garden in West Melton. Finding seeds was more difficult and I ended up bringing seed from England. It spent a year in a cupboard before I decided where to actually plant it but I had an excellent strike rate in raising the seeds in early spring and managed to produce nearly 100 plants.

Woad has an interesting growth cycle. I describe the woad plant as looking a bit like a dock plant in that it has wide floppy leaves and grows in a ‘rosette’ in its first year, although the leaves are actually more like sorrel or even spinach – much softer than docks. You dye with the first year’s leaves and then the second year it shoots up a stalk which will produce flowers and then seeds.

The other thing to know about woad is that its pretty demanding on the soil. Most sources recommend enriching the soil first with a goodly amount of compost. Once its produced seed in the second year you can recycle the plant material and refertilise the soil and/or rotate it with another crop. I picked the woad leaves for dyeing in mid February (southern hemisphere y’all).

Dyeing with fresh woad

I did my first batch of woad dyeing in mid February 2022 i.e. end of Summer. I went into the garden with my dyepot and ripped off leaves until the pot was pretty full, packing it down a bit as the leaves are going to wilt a lot. I never took all the leaves off any one plant – and only used about a quarter of the plants I have.

I used the following equipment

  • A large pot for dyeing in. Mine is a black enamelled pot with a lid. I only ever use this pot for dyeing blues (I have other pots for red and yellow).
  • A scale for measuring weights of leaves and material to be dyed.
  • A kitchen thermometer – these are often sold for jam. Not the kind you stick into your roast meat. Again this is kept solely for dyeing.
  • A notebook for noting weights, temperatures time etc.
  • A long stirrer (wooden spoon or similar).
  • A whisk or hand beater.
  • A large sieve or strainer is useful.
  • An alkali such as washing soda.
  • One package hydrosulphite (found in some dye removers – I used Rit but do check).

Extract the dye liquor

I weighed the leaves and it came to just over 2 Kg (although they were a little wet with dew). I then rinsed them to get off any dirt and while doing this eliminated a small selection of weeds. Finally I tipped almost boiling (90 degrees C) water over the woad leaves in the dyepot until they were just covered and left it to stew for a couple of hours.

When I got back the pot had come down to about 50 degrees C which is perfect. Once you start the dyeing process you must keep it at 45-50 degrees. Remove all the plant material from the pot, squeezing all the liquid out of it as you go.

Pot of woad soaking.

Now you should have a pot of brownish greenish liquid that is not at all appetising. Check the temperature and if necessary bring it back to 45-50 degrees C.

Prepare the fibre to be dyed

Weigh your fibre (yarn, cloth etc.) and note it down. Mine came to a bit over 200 gm and included several skeins of spun yarn including a coarse wool (Perendale?) and a mix of Polworth and Alpaca. 200 gm to 2 Kg (2,000 gm) of yarn means that I have a 10:1 ratio of dyestuff to fibre which should mean good colour.

If you have skeins of wool make sure that they are not tied too tightly or your dye will not apply evenly. If they are hand-spun check also that the ends are not tied tightly around the skein bundle. But you do want the skeins tied so that you can pull each out of the dyebath without them getting looped through each other and creating fuss. Two or three figure of eight loops should be sufficient.

Now soak all that fibre in a warm water bath. This drives all of the air out of the fibre so that adding the fibre to the dyebath doesn’t also add oxygen to it – the role of oxygen in dyeing with indigotin is critical and you need to control for this.

Alkalyse and Oxygenate

Dissolve 10 gm of washing soda in a little warm water and add it to the warm dyebath.

Now take the whisk or hand beater and whisk the dye bath vigorously for a couple of minutes – this is done to introduce oxygen into the dye and ensure that the whole bath is oxygenated.

You will see a froth develop on the top of the dye bath and in a second or two it will turn blue – as in this image. This is great – we can see that our idigotin dye is ready and willing. Unfortunately in this state it won’t penetrate the fibre so before we can dye with it we need to pull that oxygen out again.

Reduce

We use the hydrosulphite chemical, a ‘reducer’ to deoxygenate the dye bath. When working with indigo there are fermentation methods for achieving this which may well work with woad as well (its the same chemical after all) but using the hydrosulphite it easy and fast.

Take your package of Rit dye remover or similar and sprinkle the white powder over the surface of the dye bath – you can gently stir it in but be careful to minimise disturbance to the dye bath – from here on in you need to be very calm and gentle with it to avoid adding any oxygen so put away that whisk.

It may start to form floaty patches of blue on the surface (see photo) – this is the bloom and is a good sign.

Dye pot showing bloom – note also thermometer hanging at the side of the pot for constant monitoring.

Leave it for about an hour (keeping it at that stable 45-50 degrees) and when you return the liquid will be a clear yellow. Now you’re ready to dye.

Dyeing with woad

Caveat: there are two important things to keep an eye on throughout the next process

  1. try to keep the dyebath at that 45-50 degrees. This may mean occasionally returning it to a heat source.
  2. be as careful as possible to avoid adding oxygen to the dyebath. This means minimising drips and ensuring everything that goes in goes in damp (the water in the fibre is better than having air in it).

OK, now squeeze excess water out of your fibre and gently add it to the yellow dye bath without rippling the surface. Let it soak for 20 minutes, stirring gently occasionally to ensure the dye gets right through it. If bits float to the surface gently poke them down.

After 20 minutes gently pull each item out while carefully squeezing the dye liquid back into the bath without any dripping. I do this by holding one rubber gloved hand right above the surface and using it to squeeze it out while the other gathers the material up.

Woollen yarn soaking in the bright yellow dye – note little floating patches of blue on the surface.

Watch in awe as the magic happens – your fibre will come out of the yellow dye bath a buttery creme colour which will quickly start to pale to white and then turn blue as it contacts the oxygen. Let it stay in the air for 10 or so minutes while you open it up to ensure all the fibres are getting access and turning blue. Once the colour has fully developed you can return it to the dye bath – more dips will result in both more even dyeing and a deeper blue.

One final thing that I did was dip each in a bath of water with a splash of vinegar in it. This had been suggested to balance the alkalynity of the dyebath.