Dyeing Wool with Dried Japanese Indigo Leaves

Rather to my surprise, I have found Japanese Indigo plants grow well outdoors in South Wales. They do have a sheltered, fairly sunny spot in my garden and their border is raised a couple of inches out of the wet clay with plenty of sheep manure dug in. I also have more plants in grow bags in the greenhouse. It is worth giving them the space because not only do the plants mature earlier, I think each harvest gives a greater amount of indigo dye, weight for weight of fresh leaves, compared with the outdoor plants.

On the downside, under glass, Japanese Indigo needs to be fed and watered regularly. My greenhouse has been neglected since last August, so this is how it looked in January. Oh, the shame of that idle watering can next to a desiccated crop. I went out there one bright, cold day, intending to clear out the dead bodies and ended up spending the whole afternoon just picking off the dried leaves. My companion, Elinor Gotland, came out to investigate.
"Duw, I'd have thought you'd have the whole greenhouse cleaned up by now. It's getting dark, the dog wants a walk and himself's dinner isn't started. What have you been playing at?"

"These leaves look blue, almost a turquoise colour. I've heard of people drying indigo leaves on purpose, to dye with later. Maybe something might be salvaged from this lot."
"Cut your losses, Beaut, repentance always comes too late. Now come indoors and put the kettle on." And thus, my bag of 100g dried Japanese Indigo leaves sat in the kitchen, abandoned for a second time.

I am still not finished in the greenhouse, in fact, last week, when I could have got back out there, I spent a day dyeing with dried indigo leaves.
First, I boiled them for twenty minutes in a big pot of water, inside a bag made from net curtains.
Elinor was appalled.
"That pot is far too hot, Beaut, everyone knows you mustn't heat indigo over 55 degrees Centigrade, it destroys the pigment."
"I found this really excellent blog by Deb McClintock, it was John Marshall who translated a recipe from the Japanese and told her to boil the dried leaves."
Elinor looked at the steaming bag of soggy leaves and the dark brown water they had left in the pot.

"Looks like a giant teabag, only no-one wants to drink greenhouse grime. Brew us some proper tea or go down the garden and hose the rest of the muck off the glass, don't waste your time washing dead leaves."
"Deb says to discard this water. I might put 50g of alum mordanted Cheviot wool in there, give it a simmer, see what happens."
"Then I'll make my own tea, thanks very much. Can't trust you not to stick a bit of wool in my cup."

The next step is to extract the indigo from the boiled mush. Like Deb, I started with about 100g of leaves, so I followed her instructions exactly, measured out two litres of water and dissolved 4g of soda ash and 6g of thiourea dioxide in two jam jars of hot water, poured them in to the pot, added the bag of leaves and turned up the gas.
"Boiling again! And you're stirring the pot, surely you know you mustn't stir indigo after adding the deoxygenating agent. Did you whisk it up first?"
"No, Elinor, no whisking, no waiting, this dye vat is singing to me as it bubbles - breaking all the rules and damn the consequences."

I stood there stirring and endured twenty minutes of her droning on about the folly of flogging a dead Indigo plant and me hardly being cut out for wild rebellion and her expectations of tears before bedtime. Then there was blue. Tipping the first, deep yellow extraction bath into a separate pot, a froth of indigo bloomed on the surface and as I pressed it inside the colander, I saw the net bag of leaves had been dyed pale blue. Much encouraged, I repeated the extraction process two more times with 2g soda ash and 3g thiourea dioxide. Pouring the third two litre extraction into the collecting pot, I checked the temperature and the pH of the final vat. Seventy five degrees Centigrade and pH8. Far too hot and not alkali enough - if I were playing by the normal rules.

"So, what are you going to try dyeing? An old T shirt?"
"In for a penny, in for a pound, Elinor. I've divided up and soaked 200g wool tops from John Arbon. I've had it for ages, I think it's Captain Poldarles - Polwarth and Merino D'Arles blend."
"Now I know you've lost the plot. That wool is legendarily soft and dreamy to spin. Only it won't be after you've felted it in that hideous death pot of hot alkali. Last time you dipped merino tops in an indigo vat, the wool was ruined, completely matted."
I stood my ground.

"Last time, I pegged the tops out on the line on a windy day and gave each piece repeated dips. This time, every 25g portion will have one five minute dip and then lie flat to air through. If you don't agitate me, I won't agitate the wool fibres and everything will work out fine."
And it did. Elinor went off in a huff to do lunch with her agent while I worked my way through dipping all eight 25g portions of Captain Poldarles in the vat, getting a series of successively paler blue dyes as the indigo was used up.

That evening, I soaked them with a splash of vinegar to neutralise the alkali, gave them another rinse and a spin dry and left them on a rack. 

Thanks to Deb McClintock, my Japanese Indigo plants did not die in vain, they dyed in a glorious cause. Deb was right about the first rinse bath too. I should have discarded it.