I've been saving onion skins to make a dye bath for a while now and have a quart jarful.
I have a way to go.
In the meantime, I thought I'd give coffee-dyeing a whirl with this white cotton top that I wear only about once a year -- so it seemed like fair game.
It soaked in cool water with 1/2 teaspoon of alum added to act as a mordant.
It never made it, but it's OK because I sort of like the softness of this latte color. May as well experiment with a different plant dye on this same top at some point. Maybe the coffee dye will serve sort of like paint primer and the next color will cover really well.
Has anyone achieved a rich, dark brown and what plant material did you use?