Thursday, April 18, 2013

Woad & Japanese Indigo Procedures

Yes, I know it’s not the right time of year for dyeing with fresh woad but I did my talk on Backyard Dyes for my guild today and there were requests for the whole story on how to use woad. I’ll include the addendum as to how to alter the procedure for Japanese indigo as well. A Two-Fer! Instead of linking to an old post, I’m reprinting it all here with a new link in the sidebar. And I couldn’t resist the following photo which is the darkest blue we ever got with woad on wool.


Damselfly’s Detailed Woad Procedure

Just as a reminder we’re going from leaves straight off the living plants to dyeing fibres (yarn, cloth, what-have-you) all in one single day. It usually takes about 4 – 5 hours total, depending on how much gets dipped and/or how long the dye content holds out.

  • Put large stainless dyepot filled about 1/3 full with water on to boil, maybe 6 litres in my pot.
  • Harvest a large bucket of woad leaves (around 700g). I pull off the good mid-sized leaves from the rosette, not the new babies nor ancient bug-chomped ones.
  • Wash leaves under cold water to remove any dirt or animal life. Slugs, sowbugs, earwigs etc. do not add to the colour!
  • No need to chop the leaves. Whole is fine.
  • Add vinegar or acetic acid to the water in the dyepot to get a pH of between 4 and 5. I do verify with pH test strips. Another step you can perhaps skip but it works for me.
  • When it’s at a full boil, add the leaves to the pot. Stir and bring up to at least where you see bubbles coming up between the leaves and they are starting to turn from bright green to a more “cooked” tan-green. This should take only a minute or two.
  • Immediately cool the pot. I put a couple of frozen 2-litre pop bottles of ice in the pot which is also standing in cold water in the sink. You want to lower to 50C as fast as possible (preferably under 15 minutes).
  • Strain out the woad leaves (which can be saved for a more conventional mordant dyebath or composted) and squeeze to get all the juice.
  • Add soda ash to the liquid to bring the pH up to between 9 and 10. For my pot it took about 15ml (3 tsps) to make the vat turn from sherry-coloured to greenish.
  • Beat, whisk or pour from one bucket to another until the froth turns from green to blue and back to green again. This should take between 5 and 15 minutes. Of course it doesn’t always follow that sequence and there’s no need to go beyond 15 minutes max. Sometimes there is lots of froth and sometimes not so much. Give the pot a few minutes to let the froth subside. If it’s really bad you might have to scoop some off. Save for blue pigment for fabric paint or something.
  • Check the temp and raise again to 50C if necessary. The vat should be murky blue-green with floating blue particles.
  • Add thiourea dioxide to remove the oxygen and “reduce” the vat. For my pot it usually takes about 10ml (2 tsps). Don’t use more thiox than necessary or the vat will strip the blue out as fast as it puts it in. (Ask me how I know!) Stir in gently and leave to rest for 40 minutes to an hour.
  • After that time the vat should have a purplish bloom or flower on the surface and be clear greenish-yellow underneath. If that’s not the case (still murky), add a teeny-tiny bit more thiox and let rest a little longer. If necessary warm it up to 50C again. If it’s already clear yellow-green but no metallic sheen don’t add more thiox. There’s probably just somewhat less indigo in this vat so the sheen doesn’t form.
  • When the vat is fully reduced, gently introduce your wetted-out fibre, cloth or whatever without disturbing things as much as possible. Poke anything under that pops up. Allow to remain in the vat about 20 minutes.
  • Remove fibre carefully without dripping back into the vat. Try to squeeze out under the surface with gloved hands. Place dyed fibre immediately into a bucket of water (either cold or warm if desired to prevent shocking wool). Swish around a little, squeeze out and hang fibre to oxidise for at least 10 minutes before redipping.
  • Dips can be repeated as many times as wanted for deeper shades. The first dip can be splotchy and uneven but the second evens things out. Any more dips and it seems to start stripping colour instead so I usually don’t go past 2 or 3 at most. If you want, you could leave the last one in overnight. It won’t hurt.
  • Finally, allow the fibre to oxidise for at least a couple of days before washing and rinsing to remove any unfixed dye.

Damselfly’s Japanese Indigo Procedure

This is exactly the same as for woad except:

  • Leave out the vinegar. I’m not sure if it’s necessary here but I haven’t done a more scientific experiment to prove my theory.
  • Begin with a pot of cool water, add the leaves and bring to a bare simmer, stir just until the leaves are “cooked”.
  • Carry on with the rest of the steps. The bubbles should show blue fairly quickly but continue to aerate for 5 minutes or so.
  • There’s somewhat more indigo than with woad. That lovely purple metallic sheen should definitely form on the surface.

So there ya go!

1 comment:

pao said...

Wow! How cool is all that?!