When you spin a single that will stay a single and spin a single that will become a plied yarn, do you spin them differently? I do.

I've heard and read that singles can lose around 30% of their twist when plied, so you should always add more twist to the singles. I wanted to see how true this was for my spinning, so I did a little experimenting.

I spun some singles to keep as singles and some singles to make a 2-ply, without measuring them along the way. I found out some interesting things, just by measuring twist angle.

The natural colored samples are all oatmeal-colored BFL, spun with a woolen draft on a wortsed preparation (commercial top)

Singles to stay singles
I spun my singles lightly. I knew I wanted a soft yarn in the end with lots of air. I made a sample card when I got to a singles I liked and also did a a plyback sample. Just looking at the plyback sample tells me that this is not a yarn I'd want as a 2-ply.

I kept some yarn unfinished and finished a bit, then measured both. I snuck in a second little experiment: finishing. I know that a yarn relaxes when it's set, meaning it loses some twist in this part of the process, but how much?

Here are the stats on my singles that will stay singles:

Fresh singles:
- 23 degrees of twist
- Set singles (hot water soak, snap and hang): 20 degrees

That's just under 13% of difference in the amount of twist.

I plied some this singles yarn -- a 2-ply that's a little over balanced-- to see what it would look like. It's not a yarn I would want to knit. It looks like it would break with and friction or tugging.

But how much?
I made a sample card when I got to a singles I liked and did a plyback sample.

Here are my stats for 2-ply:

Fresh singles: 32 degrees of twist
When I measured the twist angle of the plied and set yarn, I picked the yarn apart and measured a singles. There is no way to do this without introducing twist back into the singles as you untwist the ply. I tried to pull them apart, rather than twisting them apart. I did not compensate for this in my measurement. It is likely that the twist angle should be a degree or two less than what I measured.
Plied and finished singles: 24 degrees

A difference of 25%!

So yes, I am happy and confident saying that a singles that will be plied needs more twist than one that will stay a singles -- more twist means approximately 25%-30% more.

As usual, the instant I was done with this experiment, I was ready to do more. Is there a difference with a worsted draft on a woolen prep or woolen on woolen? What about adding more plies? What about different fibers? What about the degree of twist in the final ply? Type of finishing?

Instead I spun a singles to stay a singles, and as a 2-ply, out of commercially prepped and hand-dyed Polwarth. The fiber is top, the draft is woolen and the colorway is Forest of Pies by Spunky Eclectic. Other than the gorgeous dye job and fiber, the difference with these yarns is that I spun them with an end use in mind, so my spinning was more focused on the end yarn than the experiment. I find that sometimes makes a difference. When I spin or knit for sampling or swatching, I can make the numbers work how I want them to because I am focusing on the experimenting/swatching. Then when I spin or knit for the project, my numbers can be different because I'm more relaxed and focusing on the project.

I spun a 2-ply and set it with hot water, snapped and hung, and spun a fine-ish singles that I fulled slightly in the finish.

- My singles was 23 degrees fresh and 20 degrees set, a difference of 13%
- My 2-ply was 34 degrees fresh and 25 degrees plied, a difference of 27%

I also knit with them.

A pair of mittens for the 2-ply:

And lace for the singles:

Now I know better where to look if I have a singles yarn that skews when knit or a 2-ply that breaks when knit: in the singles twist.