I recently pulled my fabric bundles from the solution they were soaking in. Above, you can see a piece of bark exposed. This alum soaked cotton broadcloth was wrapped around fragments of bark from the Ponderosa Pine trees that surround my home. The fabric was boiled for several hours in a liquid resulting from bark and water being boiled for 4 hours or so.
One side is much darker - the one that was exposed to the air during drying.
This bundle will be left to air dry. I will not unwrap it until it is dry all the way to the center.
I am just messing around - experimenting. I don't have any books on dyeing with native plants, but I should order one or two. I have a couple on my wish list, but I have not bothered to invest yet. I am enjoying the experience of my own discovery process.