Another factor causing waste is second cuts. This is usually not very important in wool judging, but is a serious problem to producers. It is caused by a shearer cutting the wool fibers two or more times. These bits of wool, second cuts, or noils must be carded out or they make slubs in the finished yarn. Of the two, clean weight is the most important.
All wool is sold on a clean basis whether by grease weight price or clean weight price.
Yield or shrinkage is used to determine what the grease price will be. Both methods cost money and require time. Therefore, learning to estimate yield is very important in wool judging. A wool buyer has to estimate yield to calculate the grease price of a wool clip. Depending on these factors shrinkage of wool varies greatly.