Choosing the Right Yarn

This week's post is brought to you by Rachel Brown of Porpoise Fur. She'll be writing a monthly guest blog series of tutorials for us as she is a proper knitting, spinning and fibre guru. You can read more about Rachel's story here. We're kicking this off at the very beginning, with an in depth look at fibre and how it plays a big role in the outcome of your project.

Choosing the right yarn
Have you ever spent weeks or months working up a beautiful handknit sweater only to have the finished object pull out of shape and be unwearable within a few outings? Ever wondered why everyone else’s gorgeous crocheted market bag looks great and holds up when yours comes back from the store with snags and holes? Today we’re going to talk about why it’s important to think about yarn choice for projects, and what factors you can control to make sure that your finished object is a success.

Usually a pattern will specify using a particular brand of yarn. This does not mean you must use that yarn, but it’s important to choose a replacement that has similar characteristics to the yarn used by the designer – they’ve usually chosen that yarn for that design for a reason! The designer will have swatched with the yarn, thought about what stitch pattern will work well, and will have tested out alternatives. If you choose a cotton/bamboo blend with almost no elasticity for a pattern that uses 100% wool and includes lots of cables, you’re going to be disappointed.

The natural fibres used in yarns fall into two main categories: protein fibres and plant fibres. Protein fibres include wool, mohair, cashmere, alpaca, llama, and silk.  Plant fibres, as the names suggests, are derived from plants. These include the obvious candidates like cotton and flax, but bamboo, Tencel, Rayon and acetate are also plant fibres. These fibres all have certain characteristics that define their yarns, and affect the resulting knitted or crocheted piece that you make. I’d like to go through two of the key features that vary between yarns made from different types of fibre, and talk about what characteristics need to be considered to get a successful finished object.


Have you ever picked up a skein of yarn and thought “Wow, this yarn is really bouncy and squishy”? Some yarns are super plump and elastic, and will stretch and return back to their original length easily. Most often these yarns are made from wool, which has a number of traits in the individual fibres themselves that contribute to the yarn’s elasticity. The major contributor to wool’s elastic nature is crimp, which is an indicator of how wavy the fibres are in the fleece. Wools with high crimp have many bends over the length of the fibre, while wools with lower crimp may have only one or two. You’ll probably recognize some of the breeds associated with high crimp, such as Merino, Cormo and Polwarth, to name a few. High crimp wool tends to be finer (smaller in diameter) then low crimp wool, so not only are these yarns elastic, they can also be very soft.

The other determining factor in the elasticity of a yarn is the way it’s been spun. Yarns that have lots of twist and are tightly plied tend to be more elastic and stretch-resistant then yarns that are lower twist, or are more loosely plied. This is due to the extra energy stored in high twist, tightly plied yarns, which enables them to resist stretching and bounce back to their original length and shape.

Usually these super bouncy, elastic yarns will be 100% wool or have a very high percentage of wool. They may also be tightly spun and plied. These yarns a great for patterns needing lots of stitch definition (cables, textured patterns), and will keep their shape through multiple wearings without stretching out too badly.


The second characteristic to consider, both in the yarn and the finished fabric, is drape. I think of drape as the fluidity of the fabric, how it moves in space and how it flows over the body. Some yarns lend themselves better to drapey, slinky fabrics – think of yarns containing linen, silk and bamboo, for example. This is because of two factors: these fibres have virtually no crimp, and the length of the fibres used in the yarns is very long, so they require very little spinning twist to stay together. The results are yarns that flow like water in the crafted fabric. Rayon and acetate also fall into this group of long, drapey fibres. In addition to many of the plant fibres, protein fibres like mohair, alpaca, and llama tend to have less crimp and elasticity then most wools, so they will also contribute a drapey factor to their resulting yarns. This is also true for wool yarns made from longwool sheep breeds like Wensleydale and Teeswater; although these wools still have crimp, the crimp is very loose, giving these yarns drape far above their crimpier cousins.

Drapey yarns are ideal for shawls, for lace, for flowing sweaters that don’t need to be form fitting. They are not great for things like socks or closely tailored garments that depend on keeping their shape to looking good.


Cotton is a bit of an oddball out in this discussion. Although it is a plant fibre with no, if any, discernable crimp, it’s also a very short fibre, so it tends to be spun and plied tightly to keep the yarn together. This means that cotton yarn tends to very low on the spectrum of elasticity and drape. The yarn doesn’t bounce back once stretched, and it also tends to be very dense, so cotton items are quite heavy, leading to a greater tendency to sag and fall out of shape. The shortness of the fibres means that, except when worked at a very fine gauge, cotton yarns don’t have great drape either, and the resulting fabric is stiff and unweildy. This leaves cotton as a good candidate for things that need to be sturdy and strong, but don’t necessarily need to hold their shape or fit particularly well: dishcloths, baby blankets and bags spring to mind as good candidates for cotton yarns.

That being said, cotton is great in blends with other fibres. When combined with crimpy wools, cotton gives a yarn that can be great for warmer weather tops and accessories, as the wool adds some bounce and memory to the yarn. Go the other direction and blend cotton with bamboo or silk, and you’ve got a strong yarn with excellent drape and swing.

The key to choosing the right yarn for your project is to try to match the yarn characteristics of the original sample as best you can. Take a look at the fibre content and construction of the suggested yarn and think about why that yarn was chosen by the designer. Find yourself a close cousin to that suggested yarn and you’re on your way!

Comments 5

Quinn Baltus on

So detailed. Thank you. I do wool tapestry weaving work and am often surprised at the different qualities of the wools as I layer them. I will read the composition on the labels much more carefully.

Orissa on

Amazing article! So informative and well explained. I’ve never understood how to pick yarn, and as a mechanical engineer, these explanations really made scientific sense!

Deborah Kay Lewis on

I am going to use these principles when matching my stash to new patterns (not just choosing the colours I like). Hopefully more successful results in the future. Thanks

Lorna on

Super article for explaining how yarns will work (or not!)

Jacqueline Knight on

I really appreciate this info thank you

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