In the previous post, Twists and Plies Part 1, you read about twists as it pertains to yarn and how it affects crochet stitches. Another consideration is the ply of the yarn. As the yarn strand comes off the spinning wheel or machine, it is twisted to make it stronger or thicker. A yarn is plied when two or more strands are twisted together. These strands are twisted in the opposite direction than the way they came off the wheel. This means that if the original strand is twisted in a clockwise direction (Z twist), then the strands are plied together in a counter-clockwise direction (S twist). The opposing twists keep the strands together.
In the US, the number preceding the word “-ply” indicates the number of single strands of spun yarn that are twisted together. Some countries use it as a shorthand for the overall thickness of the yarn. As we will see, a large number of strands does not necessarily make up a thick yarn. Plying strands together can create a whole new look to the yarn with the addition of textures and colors. The addition of more strands enhances durability and sometimes weight. Many yarn enthusiasts can tell from the number of strands in the ply how well the finished item will turn out.
There is even a different shape to the yarn when looked at in cross-section, and this shape can affect stitch definition. Some examples include singles =roundish but flattens easily; 2-ply = oval, soft stitches; 3-ply = rounder but does not flatten.
Fingering weight singles
2-ply chunky weight
3-ply in chunky, worsted, and sport weights
There are more types of plies like 4-ply, 5-ply and multiples; there is chain ply – also called chainette — and cabled ply. Multiples generally are spun from very fine yarn in an S twist, then pairs of these are spun in a Z twist. Finally, the pairs are spun in 2s or 3s in another S twist. Even though these contain multiple strands of fiber, the overall weight is reduced because it starts with very fine yarn and includes a lot of air space. A single of the same size would consist of solid fiber instead. Chain plies are used with fibers with little elasticity, such as silk, linen, bamboo, and other plant fibers, because the construction gives the fiber a bit of stretch.
4-ply in worsted weights
Yarn with multiples, 12 altogether.
Cotton Classic with a chain ply which allows the cotton to be more elastic than a cotton like Sugar and Cream which is a 4-ply.
As you can guess, singles are much more likely to show signs of weakness–you can pull the fiber apart from itself. They are susceptible to pilling and wear. 3-ply yarns are perfect for projects that get a lot of wear and abrasion, like socks. A recent trend has been to use yarns that are not plied at all but the strands simply lay next to each other.
Unplied yarn, left Red Heart It’s A Wrap, right Katia