Cold Water and Vinegar Dyeing with Woad and Japanese Indigo Leaves

Yesterday morning, the sun shone after a wet week. Inspecting the raised border in my front garden, I realised that though I can rely on the Japanese Indigo plants to crowd out most weeds, a random self-seeded courgette hidden among the rhubarb had started spreading its leaves over their heads.

The garden has been coming on exceptionally well, thanks to a bitterly cold winter and a warm, dry spring, both of which have seriously hindered the local slug population. In the midst of much smug self-congratulation, I bent down to weed among the woad plants at the front of the border and found the wretched beasts had taken their chances during the rain and slimed and climbed up the boards to eat half my leaves.

Deciding to make the most of what woad was left, I put some sections of merino and silk tops in the sink to soak while I walked the dog. In the past, I've used a method of extracting dye from Japanese Indigo leaves which only uses cold water and vinegar, so when my harvest only amounted to a modest bowlful of leaves, hardly worth a proper vat, it seemed a good time to find out whether this simple method would work on woad. The leaves had a quick rinse under the cold tap then were torn up and buzzed in a blender with ice cold water and poured into a bowl with a glug of white vinegar. After standing for half an hour, the green slush was squeezed, massaged, sieved through a cloth into a fresh bowl then the last of the juice was squashed out of the pulp through the cloth.

I put in a 15g section of wet merino and silk tops and left the bowl in a cool spot while I added another litre of cold water and vinegar to the lump of leaf pulp and left that to stand for another half an hour before repeating the squeezing and sieving and adding more wool to a second bowl.

Meanwhile, not a lot was happening in bowl one, where the wool tops were sodden with green juice, but not appreciably blue. After an hour, I squeezed out the fluid and encouraged by the sight of pale turquoise, put in my third length of tops to get the benefit of whatever indigo might still be available.

At the end of the process, none of the three lengths of fibre appeared strongly dyed and I suspected that once they had been rinsed, I would have even less colour to show for my efforts. Still, they hadn't been enormous efforts and I'd got quite a bit of gardening done in the intervals. Maybe June is too early to harvest woad, despite the warmth earlier this year. The Japanese Indigo plants had definitely already developed indigo within their leaves, I could see dark blue staining wherever I had bent or bruised a leaf while weeding. The afternoon was still young and I had all the kit out, so I cut a bowlful of Japanese Indigo plant tops weighing 300g and repeated the whole process for the sake of comparison.

This time, the fluid seemed more viscous and blue green and after an hour soaking, the first 15g strip of fibres had turned a more convincing blue beneath the surface sludge.

The Japanese Indigo was working so much better that I didn't stop after dyeing twice with the first pressing and once with the resoaked leaves. I combined the two bowlfuls and left another section of tops in there all evening, took that out and put yet another bit in to soak overnight. This morning, the wool was a much more familiar indigo blue and the fluid still looked as though there was oxgenated blue indigo in it, but enough is enough, I chucked it out. There's plenty more leaves growing in the garden and I'm not convinced these cold indigo dyes fix as well and are as stable as the blues from a hot, deoxgenated vat.

Here are the results of the cold water and vinegar method, woad at the top and Japanese Indigo at the bottom, first pressing then second pressing of leaves followed by dyeing in the afterbath.

I won't rinse them til tomorrow, so I'll have to add another picture later to show the colours once the residual leaf slime has come off. First thought - woad leaves don't work nearly as well as Japanese Indigo for this method, in future, I'll process them properly or not at all. Second thought - Ionger soaking gives stronger colours when using Japanese Indigo. Third thought - I really mustn't neglect to do a proper light fastness test this time. Fourth thought - slug pellets.

The washed tops.