Spinning relies to two process – drafting (pulling) and twisting. The spinning frame further drafts the roving and then immediately imparts twist before winding the single onto a bobbin. Twisting provides a degree of strength to a very fine bundle or thread of fibres. The finer the single, the more challenging it is to spin and ply and the longer the process takes. This is why finer yarn is more expensive to make. There are many variables in the spinning process – level of draft, roller pressure and speed, spindle speed and amount of twist.
Here is where all the preparation really pays off and the quality or lack thereof really shows. All second cuts show up as slubs or lumps and short or brittle fibres cause endless breaks in the single.