Understanding Twist Angles

source

Why would you want to measure twist? Suppose you spun a lot of yarn at one time, all the same way. You work on your project for time, then set it aside. A year or more later you come back to it, determined to finish it--but you find you don't have quite enough yarn spun. You've got the fiber, so you sit down to spin it. 

Here's another problem--you can't spin the yarn just the same because your spinning style has changed in the meantime, and the amount of twist you put in the yarn is different. You try some of the newer yarn in your project, but it looks so different from the old that it just won't work.

By measuring the twist angle of the original yarn, you can check your new yarn against that angle while you spin. That plus 'wraps per inch' will help you duplicate yarn no matter how long it's been since you spun the first one.  (taken the HJS Studio website- link given below)

The entire article can be read on the HJS Studio website.