A common stumper for many spinners working on producing yarn to a specific thickness involves the question of plying structures. How many plies do you want? How do you know how thick or thin to spin your singles if you know how many plies you want to use?

When you get right down to it, the best answer to this series of questions is to do a series of samples. A couple of years ago, I did just that while designing a yarn for a friend (read more here). Sampling is the only way to be sure. There are lots of variables between fiber and preparations, and even more things that vary from spinner to spinner. There is no single formula that will answer these questions for all possible cases. However, there are some generalities it can be useful to know.

Singles yarn

First, let’s talk about structure and define our terms. A singles is, well, a single strand if you’re a handspinner. At its most technical, some define it as being a yarn which is twisted in only a single direction, so you can technically have yarn composed of multiple strands, but if there’s only one direction of twist it’s still a singles. There are contemporary yarns spun at the mill which are like this — roller-drafted down to being very fine, assembled with multiple strands, then introduced to twist. I can’t really think of a good and functional way to replicate that as a handspinner though, or of a good reason to do so, but it’s relevant to the question of what a singles yarn is.

2-ply yarn

3-ply yarn

A plied yarn is one where multiple strands of yarn — already spun yarn — are put together and twisted in the opposite direction from that in which they were first twisted. A 2-ply yarn has two strands; a 3-ply yarn has three. A cabled yarn is a plied yarn which is plied again in turn, going back the other way from that in which it was first plied (so, the same direction as the singles were spun). There are lots and lots of other plying structures, but those are the only ones we’re going to talk about right now, and we’re only going to be seeing pictures of singles, 2-ply, and 3-ply. We’re keeping it simple!

Any time you ply your yarn, you’re making it stronger. This is because twist adds strength; multiple directions of twist add even more strength. You’re also tucking some of the surface of the yarn inside, away from the elements and wear and tear. Plied yarns will always be stronger and sturdier than singles yarns. For some applications, they also bring the benefit of counteracting twist energy in the singles yarn, such that plying can eliminate the risk of bias or skew in certain types of yarn uses — like some knitting. The nitty gritty of that subject, too, we will be leaving for another day. For now, suffice it to say that more strands make a yarn stronger, and more kinds of twist make a yarn stronger.

But this is only one reason to ply your yarns. Plying can also even out unevenness in your singles — whether we’re talking about varying amounts of twist throughout your yarn, or getting a little thick and thin, or pretty much anything. Plying regularizes your yarn, and also changes how the yarn behaves, how it feels, and how finished fabrics made from it behave and feel. In general, a 2-ply yarn will have a somewhat nubbly texture — the two strands twist around each other and there are little bumps. Judith MacKenzie McCuin likes to say that a 2-ply yarn, properly plied, looks like a string of pearls.

2-ply yarn

By contrast, a 3-ply yarn has a smooth, even surface. Instead of twisting around each other, the three strands in a 3-ply spiral around a hollow core.

3-ply yarn

Yarns with more than 3 plies essentially behave the same as 3-plies; we could say “3-or-more-plies” as handspinners, but we don’t usually bother. You aren’t going to get the same kind of structural changes from going from 3 to 4 plies, or 3 to 8 plies, as you would get going from a single to 2 to 3.

Now then, if you take your plied yarn — whether it’s 2-ply or 3-ply — and then ply it against itself again, like we were saying, you get a cabled yarn. These tend to be very nubbly in texture, but extremely even in thickness.

Cabled yarn

In general, 2-ply yarns will tend to grab hold of each other, and it’s said this is a reason for their popularity in weaving. They make very stable woven fabrics. By contrast, 3-plies are a little slipperier and slinkier, so they tend to make drapy woven fabrics. Cables tend to create textural effects in weaving.

In knitting and crochet, 2-plies spread outward in the stitch, meaning they block out huge for things like lace. 3-plies tend to come together in the stitch, making a fuller fabric that is still stretchy, so they’re popular for socks, sweaters, hats, mittens, and so forth. Cabled yarns have some texture, but make a really cohesive fabric that’s stable and a little neutral, so they’re popular for textural stitch patterns or cable patterns.

So let’s look at that all again, in knit swatches that are backlit so you can really see how the fabric looks. Singles yarn:

2-ply yarn:

3-ply yarn:

Cabled yarn:

Allright. This should be plenty for you to ponder what sort of plying structure you’re aiming for, so on to the next question: how much difference is there in thickness depending on how you ply? I took an opportunity during my BFL binge recently to document some of this for you.

First, I spun these singles:

Because I’m sometimes too lazy to change my double drive bobbin, I spun all three sets of singles onto the same bobbin, separating them with a little bit of white wool of a different type — a yarn delimiter, if you will (I know — the geek is showing). Once everything was spun up, I rewound onto three separate storage bbbbins…

…stopping and changing when I got to the delimiter.

This got me three similarly-full (but not exactly so) bobbins. The leftovers would come in handy documenting things for this post.

I put ’em on my Will Taylor Kate, and plied ’em up. I ended up with a nice big skein of 3-ply yarn, a little waste skein of 2-ply, and a bit of leftover singles. I measured these all at this stage of the game.

Singles, unfinished: 42 wraps per inch

2-ply, unfinished: 27 wraps per inch

3-py, unfinished: 17 wraps per inch

So, interesting! A lot of people think the 2-ply would be double the thickness of the single, but it isn’t so. It’s thinner than that. So what about the 3-ply? Is it 3 times the thickness of the single? Nope; it’s a bit more than twice as thick as the single.

The story isn’t over, though. Washing the yarn is going to change it again. I took my plied samples upstairs — ignoring the little bit of singles for now, because what we’re really talking about here is how we want that single to look while we’re spinning it, relative to the yarn we’re shooting for in the end.

I ran a sink full of water as hot as I could get the tap to produce. I poured in a little bit of Eucalan. I threw the 2-ply and 3-ply yarns in there, and left. I went back some 20 minutes later, and gave those skeins a good swishing around in the hot water, which by now was still hot, it’s true, but not so hot I wouldn’t stick my hands in it. I pulled the skeins out, wrung them out (seriously, I did), and drained the sink, replacing it with a sink full of cold water. I rinsed the skeins in the cold water, pulled them out, wrung them out, put my hands inside the loop of the skein, and snapped it open a few times. Then I just hung it up to dry on a clothes hanger on the towel rack, and ignored it till the next morning.

That left me with this skein of 3-ply yarn, and a little 2-ply sample. I measured these for wraps per inch, to compare to our earlier numbers.

And now the 2-ply, with moderate twist, measures in at 19 wraps per inch — thickened up from the 27 it was before washing. And that is pretty close to twice as thick as the unfinished singles.

And the 3-ply came in at 13 wraps per inch — or about 3.3 times as thick as the unfinished singles we were spinning.

In general, I find a 2-ply is usually a little less than twice as thick as the single I’m spinning, and a 3-ply is usually a little more than three times as thick — but remember, there are lots of variables, and to be sure, you will need to do a sample.