I think this must be the slowest form of dyeing as it is done cold. I started with weld which wasn't very successful, but red cabbage has been very exciting.
I chopped up a quarter of a red cabbage very small and put it in a clean plastic milk bottle with the lid on. I shook it 3 times a day and let out the gasses, it was kept in the dark and after 4 days this was the result.
Now I have started 2 more one with buckthorn bark, I have kept the PH high by adding slaked lime, this took much longer about 3 weeks but I am pleased with the red colour.