Have you ever looked closely at the twist in any of your yarns? If not, you might want to. (We'll wait.) You'll quickly notice some are spun tightly, while others barely look twisted at all. The amount of twist — or the way the yarn is plied — depends mostly on the fiber it's made of (thinner ones need to be spun more tightly to stick together) and what it'll be used for (rug yarn, for instance, has to be tightly twisted since it gets walked all over). Paying more attention to twist when choosing yarn is yet another easy way to be a better knitter.
Why yarn twist matters
The way the yarn is plied can make the stitches lie in different ways, giving your projects unique looks. (Check out swatches of stockinette stitch from different yarns and you'll see what we mean.) Looser twists, like mohair for example, allow fibers to fly more freely and will result in a fuzzy texture. Tighter spun options, on the other hand, will appear smoother.
When substituting yarns, it’s important to pay attention to yarn twist because it could affect the amount of yardage you use. Let’s say, for example, your pattern uses a yarn with a loose twist, but you’d like to substitute it with a yarn that has a tighter twist. You’ll actually need more yarn because the tightly twisted yarn is going to knit up tighter than the loosely twisted yarn. Good to know!
Yarn twist can also affect the way your yarn drapes. A loosely twisted yarn will have more movement than a tightly twisted. For that reason, the loosely twisted yarn will have more drape to it. Think of it in terms of the rug yarn we mentioned earlier. Rug yarn is tightly twisted so that the fibers don’t pull apart and move as much. Loosely twisted fibers, on the other hand, have more room to breathe and move.