My previous post on July 8, 2020, explained how to identify S & Z twist easily. This post tells why it helped me reduce warp breakage. More S & Z information relating to bobbins, pirns, and weaving is in my book, Weaving & Drafting Your Own Cloth.
I was making a warp using a singles linen, probably 14/1, that I had in my stash. It kept breaking when it went around the end pegs. Actually, I could see that the thread was pulling apart. I figured that the way the spool was standing up on my spool holder was the problem: I was untwisting the yarn so it became enormously weaker. (Truth be told that was ½ of the breaking problem: the yarn was old.)
Notice the diagonal lines in the yarn and the toilet paper. They are all going in the same direction. That direction is called Z because it is the same direction as the diagonal part of the letter Z. I assume my warp thread was probably a Z twist singles.
I had my spool of yarn on the spool holder this way which was untwisting my yarn and causing it to break. It was set so the yarn was UNTWISTING as it came off the spool. This diagram shows the twist of the yarn in the opposite direction: we say S. That is because the diagonal lines are the same diagonal as the diagonal in the letter S.
I turned my spool end-for-end so then twist was ADDED which made the yarn stronger instead of weaker and the breakage stopped. (However, it didn’t make it strong enough to overcome the old age and the yarns broke instantly when I began to beam the warp! It all had to be thrown out!!)
At times you do not want to add or subtract any twist. Then you take the yarn off a spool on its side!
You can add S or Z twist when you unwind yarn from the end of a spool. When the yarn, as seen from the end of the spool moves in a counter-clockwise direction as it unwinds from the spool, Z twist is added. By turning the spool end-for-end, the yarn will move in a clockwise direction as it unwinds, adding S twist to it. (This option is not available with cones which are made to stand only one way up.) To understand S & Z twist read more in my chapter on shuttles in my book mentioned in the introduction.
Repeating the principle: which end of a spool the yarn come off from dictates the direction of the twist put into the yarn—because the yarn is coming off the end. Take the yarn off a spool on its side and no twist will be added or subtracted.
You can add or subtract twist not only by how you wind a pirn, but also by which end of the spool of yarn you take the yarn off. For consistent cloth you want the wefts to be totally consistent as to twist. However, a novelty cloth can be woven using different twists: depending on how you put a pirn on the winder or stand up a spool of yarn.