My woad plant (Isatis Tinctoria) suffered quite an extensive catepillar attack while I was away this summer. I thought it best to dye with it as soon as possible before it got all eaten away. This is my second year of growing my own woad and my old plant produced plenty of seeds to grow even more next year.
Last year I used a great recipe I found online by Finnish Dyer Leena Riihelä. The recipe can be found in Finnish at http://riihivilla.blogspot.com/p/morsinko.html?m=1. This year I combined my notes from last year with this recipe as well as a bit of experimenting for my dye bath.
I set off a saucepan with 2 litres of water to simmer and went out to collect my leaves. I weighed them (200g in total) and washed them. I boiled the leaves for a minute and then took the dye bath of the heath. I left it to cool for 15 minutes and added cold water to bring the temperature to 50 degrees. The liquid was a lovely reddish colour as I hoped for. I then strained off the leaves and added in 15 g of soda ash to bring the PH up to 10.
Then the fun part begins. You need to introduce oxygen to the bath so I poured the liquid from one bucket to another for 15 minutes until there was a layer of blue foam on top of the liquid. The colour of the liquid was a strong bluey/green.
I returned the dye to the sauce pan and to the hob, raised the temperature to 50 degrees and sprinkled 10 g of dithionite on top. I left it for 20 minutes to sit. The liquid had turned yellow and was ready to use.
I dyed a total of 220 grams of yarn; some mohair, wool/bamboo, merino/nylon as well as two small samples of silk with my woad bath. All the samples had two 10 minutes dips in the vat with left to oxidise in between. I desired lighter shades so I used quite a lot of yarn per leaves, but I am sure darker shades could have been achieved with less fibre.
I have left the vat to sit overnight and will see if there is any indigotin left today and hopefully the plants will revive themselves and produce few more leaves this summer