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?
http://creativeexpressionoflife.wordpress.com/2014/02/09/testing-raspberry-blueberry-and-red-cabbage/