I second the bleach idea. When I was a teen, I sewed and competed in a "Make it with Wool" contest every year. You had to supply a 4x4" swatch of each wool used in your piece. They would soak it in 100% bleach, and if anything was left, it wasn't 100% wool. The only thing is, I don't know how long
you have to soak it. Hope this helps.