How to dye stuff with black walnut. A good outline, and their various steps should all be followed. (Scouring, for instance, is genuinely important.)
Don't skimp on making dye, you want a pot full enough that whatever you're dyeing can be immersed with room to spare for stirring, so as to get an even dyeing effect. Yes, even if this means going to multiple trees because the most of the walnuts in your backyard are already starting to go bad....
A canning pot is a good size.
