While it may sound more like football terminology, the drafting zone is a very important consideration in spinning. The drafting zone, or drafting triangle, is the area between the spinners hands where the fiber is separated and evened out before the twist is allowed to enter. To prevent confusion due to being a left handed spinner, I will refer to the hand closest to the spinning wheel as the forward hand and the one nearest the fiber supply the backward hand.
Spinners have very different degrees of the drafting triangle. Some have a very noticeable triangle that is always present. It appears as if the fiber feeds itself into the backward hand and evens itself into uniformity before the twist reaches it, without any effort from the spinner at all. While others have their hands moving so quickly that the drafting triangle is barely visible. I tend to fall in the latter category, but I find myself intrigued by the former.
The drafting zone, whether visible or not, is where the spinner needs to focus most of his of her attention. The uniformity of the yarn is decided in the number of strands of fiber entering the drafting zone. As you prepare to spin, test your fiber by drafting a small amount and twisting it from the end. If the resulting strand is what you want your singles to look like, then observe how much fiber is being clasped by the backward hand, the one closest to the fiber supply. This is the fiber volume that you need to maintain in the drafting zone to create your desired yarn.
The length of the drafting zone is largely determined by the length of the individual fibers. The length of the drafting zone will be at least one and one half times the length of the fiber. This may fluctuate due to variations in how slippery the fiber is. It can also differ based upon the experience of the spinner.
The drafting zone is also where the texture of the yarn can be previewed. The more the fibers in the drafting zone are aligned and parallel, the smoother the resulting yarn will be. When spinning from a rolag, the fibers will be more haphazard in the drafting area, this will result in a yarn that is spun woolen.
The drafting zone is also the main line for quality control in spinning yarn. Think of it like an inspection zone for the incoming fiber. As you spin, keep an eye on the fiber as it feeds into the drafting triangle. Be on the lookout for second cuts that may not have been removed entirely, or small bits of vegetative matter that the carder may have missed. It is so much easier to stop the twist from entering the contaminated fiber so that it can be removed before it is ever spun, than to break off yarn that has been spun and try to splice it.