An important, and often overlooked characteristic of yarn is its ability to bounce back. This is often referred to as elasticity, or memory. This is certainly a desirable characteristic in garment construction, but how do you know how elastic your yarn will be?
This is where that often discussed and debated term of crimp comes in. When you hear a shepherd boast that their animals have very high crimp, it is time to perk up your ears! While less crimpy fleece can be desirable for other characteristics such as luster or softness, a crimpy fleece is all about elasticity.
Fleeces that have lots of crimp are exceptionally easy to spin and create yarn that can be quite lofty. Loft is desirable in knitted items because lofty items can insulate without being too heavy. The ideal sweater is one that is cozy and warm without making the wearer feel weighed down.
Elasticity also helps the knitter to create garments that fit better. An elastic yarn does not require as many stitch increases and decreases to keep a garment in line with the form. It also improves the durability of the finished garment. An elastic fiber can recover from being stretched without much work, whereas a non elastic fiber could not recover from a snag.
Some fibers are completely without any natural crimp, but their elasticity can be improved in the spinning process. Using a woolen preparation, pre-drafting and using a long draft can add elasticity to flax bamboo, or llama, but the improvement is limited by the fibers themselves.
Another way to improve elasticity is to blend a very crimpy fiber into the preparation. This may reduce other characteristics such as luster and softness.
The amount of elasticity should be tested prior to using a finished yarn to prevent sizing difficulties. I was never a big fan of test swatches when I knitted with manufactured yarns. The shrinkage was already addressed in the manufacturing process and care instructions. With handspun yarn, the elasticity can be deceiving. Yarn that is not completely clean can make for a nightmare if it is knitted without first doing a test swatch. Once the test swatch is knit, donít stop there, try washing the swatch to check for shrinkage. Do this by knitting the test swatch, blocking it as you would any other knitted item. Once it has been blocked, lay it out on a sheet of paper, and trace around it. Wash it as you would the finished garment, reshape, and dry. Once the swatch has dried, lay it out on the paper again, and compare the size to the original outline. This will give you some idea as to how elastic the yarn is. An elastic yarn will be either the same size or smaller than the original, while a non elastic yarn will be larger than the original.
There are times when having elasticity is less desirable. When the finished garment needs to have drape, i.e. a shawl, less elasticity prevents knitted or woven details from being obscured by yarn that is trying to draw in on itself.