Jeff
Yes you are correct about the alum I didn't think of that. I can see the need and how the alum would make the wool color fast. You are also correct about using the bark from trees. I can remember Mum using walnuts, butternuts, hemlock, cherry and maple. Back then each family did things a little different with secrete formulas to get different colors. I also remember she would brew the stuff up outside and then store it for later use.

Flap Jack