The gall nut gives a tannin and is almost colorless…a light tan. That’s an advantage. But, the other tannin sources are in my backyard.
The tannin plant material produces more or less color. And, the plant material reacts more or less with ferrous sulfate. I’d like to test their light fastness. That’s the next step. Prepare fabric samples, overdye them and put them out in the sun. That will be a good test of their lightfastness.
So, two things are rattling around. Why/what is the backyard yellow? Is it from plant material? Or is it because the plants are bio-accumulators of something which reacts with the aluminum acetate? And, how nice it would be to have a backyard red!!