As you know, I’m not a spinner, but I can talk ply. I used to teach it when I taught textiles at FIDM. It is the same principles for textile yarn as for yarn, just different scales. Once you know some basics, you can take a fresh look at your yarns, and yarn choices.
Singles are the first stage of any yarn. There is a lot conversation among those who look at yarn on what the best term is—because one ply implies additional plies, so single ply was adopted. But that isn’t satisfying to some. I think it is good enough. Singles are the what a spinner produces when they spin their prepared fiber on their wheel. This is true whether it is a spinner with a wheel or a mill.
Once there is more than a single ply, yarn is designated by how many singles are twisted into the yarn. This is not to be confused with the British system, which was based on plies, but also on weight of the yarn.
There are twisted and cabled yarns, tapes, and chainettes, but I’m just going to look at twisted or spun. Ply is spun with either an S-twist or a Z-twist. S-twist twists to the left. Z-twist is to the right.
It is easy to fall in love with single ply yarns. They are often spun from silky, long-staple fibers and they gleam and shine as they await us. There is nothing wrong with single ply yarn, but be aware of these factors:
- Amount of twist will determine the strength;
- Length of fiber will impact pilling;
- Types of fiber will impact strength and pilling;
- The yarn may bias when knit in some stitches; and
- A knit stitch will look unbalanced on the leading leg because the yarn twists differently as it goes around the needle.
I have always liked to use singles to teach people to knit because there is less danger of splitting the plies. Because the yarn is pretty, they are an excellent place to start. Singles can twist around themselves as they are pulled from the skein, essentially plying themselves to achieve balance.
Singles can be great for felting, but they can also pill because of the lack of structure in the yarn itself, but this is dependent on spin/twist and fiber. Look at how tightly the fiber is spun and know whether it is a fiber prone to pilling.
Two-ply yarns are two singles twisted. Generally, if the singles were twisted in an S- or Z-twist, they are plied in the opposite direction to give stability. Two-ply yarn is oval, not round, and this impacts what the stitches look like. This yarn will generally open up as stitches are formed, allowing the yarn to show off. It is not as good at holding up cables as it is in opening up for lace.
Now you will start seeing round yarn. Completely makes sense when you think of the structure and how the plies will interact with each other; think of it as a stool—it can stand solidly with just three legs. The surface of stockinette starts to look smooth, cables stand up, and color-work edges will stand out nicely. The roundness can be more of a challenge in lace as the stitches roll inward.
4-Ply and beyond
Four-ply yarns can be made with four plies, or two sets of two-plies then plied together. Generally speaking, the greater the number of plies, the stronger the yarn will be, but this may be relative and dependent upon the diameter of the plies and the fibers involved.
Novelty yarns are often made with plies of differing sizes or weights.
What Should You Use?
Use whatever gives you the result you like. When making substitutions, do a little research into the original yarn used. That will give you the best information for making a good substitution. How the yarn is spun and plied will impact your results, so take that computer out of your pocket, look up whatever information is available, and make informed choices!
When you make swatches or make projects, take note of what worked about the yarn choice and use it to inform future yarn choices. There are so many yarns it can be hard to choose, so let information help you. I believe each yarn will tell you what it does best, you just have to pay attention.