Everything You Ever Wanted to Know about Yarn Ply - Part 1

First for clarity, a definition from knitting about.com. "Yarn purchased from yarn stores or from individual yarn makers comes in a lot of different styles and configurations, but there are some basics that usually hold true, including the fact that yarn is typically made up of plies, or should I say at least one "ply." Plies are the individual strands of yarn that are worked together to form a plied yarn. A single strand being sold or worked with on it's own isn't usually called a ply, though, it's known as a single, because calling it a one-ply yarn doesn't make much sense. Multiple plies can be used to create a knitting yarn, and while some countries use the number of plies as a shorthand for the thickness of the yarn (a two-ply would be thinner than an eight-ply, for instance), in most cases the number of plies has nothing to do with the thickness of the finished yarn. You can have a very bulky two-ply yarn or an extremely thin four-ply yarn depending on how the individual singles were produced.To ply yarn, individual singles are spun together with the twist worked in the opposite direction from how the singles were spun. This gives the yarn much more strength, durability and consistency than is seen in a singles yarn."

To further confuse yarn novices we refer to the thickness of yarn as weight and we refer to the weight of the yarn put up. A "put up" is the way in which the yarn is presented for sale, usually skeins or balls.

The ply system of yarn weight (thickness) was typically used in the U.K., Australia and New Zealand. Again,to confuse things even further there were inconsistencies between countries. I've seen charts like this one from LoveKnitting.com.

Here in Canada we are dominated by the U.S. export market, so in the past we often saw labels using one system or the other depending on where the yarn was sourced. 

Interestingly the U.S. Craft Council has also struggled with a naming system for weights. They started with a 1-5 numbering system which has grown to 0-7. Machine knitters also use a different system based on yardage per pound. This one comes from the use of yarn on cones. 

I'm currently working on a design for release this fall which uses a single ply yarn of 100% wool. Of course, that got me thinking about the design challenges of working with a single.

Yarn is created by taking fibre and twisting it into a continuous thread. Singles can, depending on the length of the source fibre, have problems holding together when knit. Some fibres have short lengths and need more twists per inch to hold them together. Fibres with longer lengths require less twist. More twist leads to biasing when used in simple stocking stitch.You can test this out with a large swatch. The easy fix is to use a textured stitch which incorporates both knit and purl stitches.

Singles also tend to be less consistent because plying can smooth out some of the imperfections which are more easily seen in singles. When knitting with them you'll come across thicker and thinner sections. If the thin spots are of concern you can break the yarn, overlap and rejoin by splicing with moisture and friction by rubbing them together briskly while held between your palms. These yarns can appear soft and puffy. The lack of structure, can result in a yarn which has problems with pilling or shedding. Before knitting, single-ply yarns appear to have a smooth surface.The best description I've come across is to think about the difference between a ponytail (single) and a braid of hair (plied yarn). When knit up, singles tend to produce a cohesive, solid fabric which is now much stronger in nature.

Visually these yarns create stitches which are very smooth in nature. The roundness of the strand avoids the shadows which are created by multiple plies. This is especially apparent in stocking stitch.

This is the one I'm using it's Malabrigo worsted merino.


Since there's very little twist to hold the fibers of a single together avoid tugging too hard on the yarn. Tight knitters or those who put a lot of tension on the yarn may find them harder to work with for this reason. Smoother needles will also help in avoiding snagging the yarn. Some knitters will get better results with a smaller needle size for added structure to avoid pilling. They do lack some of the strength and durability of plied yarns. Due to less twist to hold the fibers together, singles can separate and grow thin in garment areas that suffer from friction. 

Garments knit from the heavier weight singles tend to feel dense and are often very warm, making for great outdoor sweaters. A common example of a single ply yarn is lopi. Modern knitters will find many yarn weights now available in singles. You can check out my Ravelry search here, it includes yarns categorized from lace to super bulky.

Part 2 is here.