Another Question

To answer the comment left on the last post, "Is there something you can do to the tannin effect so that it doesn't wash out if you want to overdye it? I tried soaking my tannined piece and it started to soften around the edges. Any advice?"

Tannin is used in natural dyeing as a premordant so I am surprised that it is washing out. Rust dyeing is sensitive to ph levels. If you are soaking it in soda ash in preparation for procion dyeing that might be what is causing it to "soften around the edges."