The warp I used for the vest fabric is Cotton Ice. Cotton Ice is a cabled yarn, which means that it is plied twice.
In this particular case, the yarn was initially spun in the S direction, one each of cotton and rayon. Then the 2 singles were plied together in the Z direction. Last step, which makes this a cabled yarn, multiple strands (3 in this case) of the plied yarn were then plied again in the opposite direction, S. As with all spun yarn, the starting spin direction can be either S or Z.
What’s important to my little story here is that the last direction this particular yarn was twisted in was S. (My typical 2 ply yarn ends with a Z twist.)
Now let me show you a couple of pictures of my selvedges…
The photo on the left is my left selvedge thread along with a warp thread a bit further in the web. The photo on the right shows my right selvedge thread along with a warp thread in the web.
I don’t know if you can see it but the left selvedge thread has become untwisted during the weaving process. Looking to the right, the right selvedge thread has become more twisted.
I once had a chenille baby blanket “fall apart” on the left selvedge. The yarn was untwisting and the fluff was falling out. All I was left was the bare threads that was to hold the fibers in. In looking at this, the chenille must have ended with an S twist.
My theory is that in throwing my shuttle from left to right, I am, ever so slightly, putting in a Z twist to the yarn, thereby, removing twist from the yarn. On the right side of the warp, I am doing the opposite — putting an S twist to the yarn, thereby adding twist to the yarn.
This is going to require a few more warps and paying close attention to what is happening to my selvedges with plain old 2 ply yarn. But it also creates some avenues of thought and experiments.