Today I have set up a test using calico (pre-mordanted with alum) in raspberry, blueberry and red cabbage dyes using cold extraction in the presence of (1) vinegar and (2) ammonia.
The berries are frozen, and the red cabbage came straight from the fridge, as I believe after reading India Flint’s book that heat can alter the colouring, whereas extracting dyes from frozen can often produce brighter, more vibrant results.
I put a teaspoon of household ammonia in the alkaline pots (it is really stinky lol), and 2 teaspoons of white vinegar in the acid pots.
I am using tap water so this will also alter outcome as it has not been filtered.
In each glass jar is one small piece of calico and also a small piece of calico bundled with the material and tied with an elastic band.
Hopefully my patience will last for a week and I’ll leave these in the shade to develop.