UPDATE:
It’s been about a year since I wrote this post when I made a batch of walnut ink. I’ve been using it regularly and it’s delicious, silky, smooth and rich. It seems to be lightfast, no signs of fading on any of the pieces, although I’ve been careful to use best quality acid-free paper like Fabriano and Saunders.
Here’s the most recent drawing, in carbon and white conte crayon overlaid onto a background of walnut ink.
So today I finally finished the walnut ink I started a couple of weeks ago. A friend gave me 4 fresh walnuts (juglans regia) in their husks. I peeled them and left the husks to stand in a basin of water for about a week and a half. They went very black and mushy. I put the basin, covered with tin foil, into a slow cooker with hot water coming up to half way and left it on the lowest setting overnight, letting it cool completely for another day and night.
Then I strained it through a ‘J’ cloth into a large jar and tested its strength on a bit of cartridge paper. It was quite pale so I boiled it on the stove and reduced it, checking occasionally until it was a decent sepia colour. There wasn’t much to bottle, about a quarter of a tea mug. The recipes I’ve looked at online suggest adding up to 20% surgical spirit (rubbing alcohol) as a preservative, but there’s so little that I think I’ll use it up pretty quickly. I’ll do some drawings with it and leave them in the light until this time next year. If they haven’t faded, I’ll see if I can get hold of a larger amount of husks and make some more.