When we send our fleeces to be turned into roving or yarn, we use custom "mini-mills" operated by friends who use no harsh detergents or chemicals, and who remove vegetable matter (VM:bits of hay, twigs, leaves inevitably stuck in the fleeces of pastured sheep) by hand or by a gentle mechanical process. Indeed, family and friends who believed themselves to be "allergic" to wool or lanolin have discovered that is rarely true. In commercial wool processing mills, VM is "removed" by exposing the wool to strong acids to make the VM brittle, so that (in theory) it will crumble out during the remainder of processing. In reality, what is often produced is yarn riddled with chemical residues and tiny prickly bits of VM, not visible to the naked eye - but definitely detectable by sensitive skin!
Another advantage of using custom mills is that we can obtain special blends in small quantities of our Shetland fleeces with silk, with our alpaca fiber or any of the new fibers such as ingeo (corn silk) and tencel. Our favorite blending genius is Gail White, who is the owner of Ozark Carding Mill, and also a nationally certified fleece judge!.