A few years ago, I learned that the plies in yarn affect knitted fabric. I thought that yarn was yarn; sometimes it had more plies than others—it didn’t really matter to me.
I’ll explore the differences between the 5 most common plies of yarn in this post: Singles, the two 2-plies, 3-plies and 4-plies.
First of all, what is a ply? It is a small strand of spun yarn that is usually twisted with other plies to create a firmer yarn. Plies (when twisted together) are what give knitting yarns their corded look.
Sometimes spinners and yarn manufacturers spin one long strand of yarn without twisting it with any other plies. This yarn is referred to as singles. Singles are weaker than other yarns and, as a result, are sometimes blended with a higher strength fiber such as nylon or silk.
When two plies are twisted together, it results in a 2-ply yarn. There are two types of 2-ply yarns: Relaxed 2-plies and Tightly Twisted 2-plies.
The first 2-ply yarn is twisted together loosely; slightly more than it would be if it was twisted together just enough to keep it from falling apart. The fabric this yarn results in is small and airy. It is generally used for knitting lace (or lace knitting; which are not the same things).
Tightly Twisted 2-ply is as the title suggests. It yields a stronger fabric that is slightly textured. As a general rule of thumb, 2-ply yarn gives a slight halo to your fabric and muddles it just a little, though there are some yarns that do not.
3-plies are made when (you guessed it!) three plies are twisted together. 3-ply yarns are among the best yarns to use; they are balanced and give high stitch definition for cables and ribbing.
4-ply yarn is almost as good as 3-ply yarn, but on plain stockinette stitch areas, the fourth ply of the yarn tends to stick out just a little bit. It’s enough to be noticed, but only if you are looking really closely and know what you are looking for. Otherwise, it is the strongest of the 5 plies mentioned here.