How to Process Fine Fleece into Nep-Free Yarn
Neps are best described as dense, tangled clumps of the short fibers of the fleece. Some people don’t worry about neps and allow them to form to add texture to their yarn, but others prefer a nep-free, smooth yarn. There is no specific advantage to either, whether you like them or not is based off a personal preference. But, when attempting to make a perfectly smooth yarn, I often recommend three things: pick a sound fleece, make sure the fleece is fully washed, and comb it versus carding it.
When choosing a fleece to process into nep-free yarn you want to make sure it is high quality. This means, you are looking for a fleece that is consistent front to back, with a low amount of second cuts, wool breaks, and vegetable matter. The higher quality fleeces have fewer short fibers, therefore, cutting back on the chances of neps forming. As far as making sure the fleece is fully washed, I mean making sure all of the lanolin is out and most of the weathered ends are removed. Any remaining lanolin in the fleece causes stickiness, making it harder for it to slide smoothly through the combs and the remaining weathered tips may break off and form neps.
My third recommendation, comb it opposed to carding it, comes from multiple outside sources, as well as, personal experience. The wool combs are more efficient at removing the short fibers, neps, noils, and vm. The more tines of the comb, the more effective it will be. This is important because even a high quality fleece will have a certain amount of unideal traits. A drum carder without a very fine cloth can cause the fibers to stretch, break, and spring back into the little knots. When carding your fleece, you have to be sure the equipment being used can properly handle fine fibers. And work in slow turns small amounts at a time. If the equipment is inadequate, the final result will be full of neps.
Taking you time in the combing/carding process is the most important part in spinning a beautiful smooth yarn.