Thank you so very much @purplemoon! With natural dyeing it is best to let the fiber have a nice long soak in the dye pot, over night, then remove it and let it hang to dry in the shade. That's kind of like a curing time. Then the fiber can be washed. The pieces of iron act as a mordant, helping the color adhere and stay fast. Wool is the best fiber to dye with natural dyes as it absorbs color most readily. Cotton is much more difficult and requires special preparation (except in the case of onion skins). With natural dyes some of them may fade slightly, over time, especially in prolonged sun exposure (not recommended), but most of them seem to stay quite well. Washing can fade them over time, but typically the items that I dye are things that aren't washed nearly as often as T-shirts and bluejeans, for instance- they are items that usually only need to be washed a few times a year.