look for small veggie matter. fine chaff. it is the devil's own to get out. large stuff comes out easily. check for weak fiber. Take a lock and holding both ends give it a good snap pull. it shouldn't break. look for what you want. Curls, large or small? Fine fleece: it will have tiny little waves rather than curls. find out the breed, the down breeds are hard to felt and make a spongy felt when done. Great for rugs and saddle pads not so great for other stuff. they are spun woolen and used for socks often. they don't felt or shrink like the finer wools. Dorset and Suffolk are down breeds. That's it for now off the top of my head.
I bought some raw Zwartble years ago, it has the smallest, tightest curl/crimp I've ever come across, and even though it looks quite clean, it has thorns and little beetles trapped in it, I can only imagine what these sheep get upto!
I separated some out yesterday, kept some 'locks' for surface effects and put some through the carder. The batt was so stiff it almost stood up straight
It looks like the mess of Texas mohair I have, fuzz and some curls here and there. I may try to put some thru the carder and see what happens. What happens when you wet felt the fuzzy mat? Inquiring minds want to know. :-)
I don't think I've ever wet felted just zwartble, I usually use it on top with other wools, but this is some raw Jacob that I separated and wet felted a few days ago, it's not quite as texturey as the zwartble, but not far off