Unfortunately my woad plants were ravaged by caterpillars this year, so I wasn’t able to harvest my usual heavy crop of woad leaves for the dyepot. The best time of year for harvesting & using the leaves is from late August/early September to the end of October. This gives the leaves time to develop their blue pigment. However, I have successfully used leaves for the dye vat at most times of the year, so it’s always worth using any leaves you can find, no matter the time of year. Also, although first-year leaves are generally recommended for the strongest blues, I have managed to obtain good blues from second-year leaves. Some of this year’s leaves were picked for a demonstration of woad dyeing in September at Denny Abbey in Cambridgeshire, where I regularly tutor natural dyeing courses. The last few remaining leaves were harvested this week in the pouring rain, ready for a woad-dyeing session with Chris Dobson, friend, fellow-dyer & plant expert. Fortunately, Chris brought with her some really large, “meaty” leaves to add to my rather pathetic specimens.
The blues Chris & I obtained from our dyeing session were as good as any from other sessions, so we were pleased with the results of our efforts. This is the method we used:
Collect about a bucketful of leaves, tear or cut them into small pieces, pour boiling water over them to cover them & leave them to soak for about an hour. Then strain off this liquid into another bucket & squeeze the leaves well to collect all the possible colour potential. Next, add enough washing soda crystals to turn the liquid from brown to green. To incorporate oxygen into the liquid in order to “activate” the blue, the liquid must then be poured from one bucket into another until the froth turns blue. Alternatively, the liquid can be whisked well. The process must be continued until the froth no longer turns blue & this can take quite some time. But persevere, no matter how much your arms ache, otherwise much dye potential may be wasted. After this pouring process, leave the liquid to stand for a while to allow the froth to subside. Then pour the liquid into a stainless steel dye pot & heat until the liquid is so hot that the heat is only just bearable to the hand. (Approximately 50C) Then add 2 to 3 teaspoons of sodium hydrosulphite to remove the oxygen & leave the vat to rest for about 20 minutes. By this time the liquid below the surface should be greeny-yellow & the vat is ready to use. Remember it is important not to introduce any oxygen into the vat, so add the materials to be dyed very gently so as not to cause bubbles. Leave the materials to soak for 5 to 20 minutes, depending on the depth of colour required, then hang them in the air to allow the blue to develop.
NOTE: More information on indigo & woad dyeing can be found in my latest book “Colours from Nature”. For further details about this book & how to order it, look under “My Publications” or email email@example.com