Select the Best Fiber for Your Garment

Have you ever wondered if you could substitute yarn in a pattern? Perhaps you have finally found a pattern for that gorgeous yarn you bought on vacation but are curious to know if you can safely substitute it for the recommended yarn. Even if you’re lucky enough to find a pattern you love written for the same weight of yarn as your favorite yarn—what about the fiber content?

There are many factors to consider when attempting to substitute yarns.


This occurs when the fiber rubs against itself or another surface. Short fibers work loose from the yarn and tangle with ends of other nearby fibers forming little fuzzballs which can only be pulled free by breaking the fibers that hold them.


This determines the ease of care of the particular fiber. It’s ALWAYS wise to wash and block a test swatch, treating the test swatch the same way you plan to treat your finished garment. Check the test swatch for shrinkage too.

Heat Retention:

A fiber’s warmth is determined by its ability to retain body heat.

The table below outlines fiber qualities and differences that can affect the outcome of their use in a garment.

Fiber Pilling Washability Heat Retention
Wool Pilling likely Hand wash. Machine wash inside out if labeled Superwash. Wool will shrink to varying degrees. Test a swatch. Will felt if not Superwash. High. Wool has the unique ability to retain warmth, even when wet.
Alpaca Pilling likely Hand wash. Will felt. High. Because of its hollow core, the alpaca fiber is extremely lightweight, and for the weight of the fiber, alpaca is actually warmer than wool.
Silk High resistance to pilling Hand wash or dry clean according to instructions. High. Sharing similar qualities with wool, silk is a warm fiber and even when wet will feel warm against the skin.
Cotton High resistance to pilling Will shrink, but to varying degrees. Test a swatch. Medium. Cotton is not as warm as animal fibers. Mercerized cotton can become even cooler, denser and less insulating. If you desire warmth from cotton, try un-mercerized cotton.
Linen High resistance to pilling Hand wash. Low. Linen absorbs moisture and wicks it away from the skin, keeping skin cool.

The Importance of Elasticity

Another important factor in substituting yarn is how fibers behave after they are knit up. Elasticity refers to “stretchiness” of a fiber. Fibers vary in how much they can stretch or elongate before they break. The ability of a fiber to resume its original shape after it has been stretched is known as “elastic recovery.” The elastic recovery helps the garment regain its shape and prevent it from becoming saggy and baggy.

The table below outlines these differences between popular fibers

Fiber Elongation Elasticity/Recovery
Wool Wool is extremely extensible and can be stretched to a third of its length, or two thirds when wet. It is able to regain its original shape. 30%-42% elasticity
99% recovery
Alpaca With only half the elasticity of wool and with less recovery, knit alpaca fabric will continue to stretch in length over its lifetime. This is why it is often blended with wool to get the best of both fibers. 15%-20% elasticity
Silk Although one of the strongest fibers on the planet, silk is not very elastic. Silk has a "slow" elasticity, and while it does stretch, it does not recover quickly and may not regain its original shape. 23%-31% elasticity
92% recovery
Cotton Some of cottons stretch may be permanent depending on the yarn, type of knitting, and wear. Over time, a garment knit from cotton will relax into the shape it is pulled into, and will lose its ability to bounce back into shape in the wash. 5.6%-9.6% elasticity
75% recovery
Linen A very strong fiber, but like cotton, lacks much elasticity. Slow to recover when stretched, and may retain the stretched shape. 2.7%-3.3% elasticity
65% recovery

The Benefits of Fiber Blends

Judicious fiber blends can capture much of the benefits of the component fibers while minimizing or off-setting their weaknesses. Is 100% alpaca too hot for you? Try a wool/alpaca blend in which the alpaca beefs up the wool’s heat retention ability a notch or two. This blend will also be more likely to retain its shape in the long term because of the super elasticity of the wool. A wool/cotton blend will be cooler than wool, but more elastic than cotton.

Superwash wool has been specially treated so that the scales on the individual fibers lie down smoothly and don’t interlock with each other. This keeps the wool from felting and enables it to be machine washed. The best way to care for superwash wool in your washing machine is to turn the garment inside out and wash it in cold water, preferably on a delicate cycle if you can. The wool will not felt, but this special attention will help keep it from shrinking and from pilling as much.

Nylon is frequently added to wool for sock yarn. The durable nylon extends the life of the wool, helping the yarn stand up to the regular rubbing socks get in the heel and toe areas. Cotton sock yarn usually has a little bit of elastic in it to help compensate for the lack of elasticity in cotton. We all want our socks to fit snuggly and not sag, so that is the benefit a touch of elastic adds.

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