Cortex and keratin: the elastic memory of wool

Beneath the layer of protective scales we've just uncovered lies wool's true engine: the cortex. It is here, at the heart of the fiber, that keratin proteins coil around each other in a helical structure — much like a tiny spring, invisible to the naked eye, but very real on a microscopic scale.

This helical structure is responsible for what could be called wool's "memory." Stretch a wool thread, it lengthens; release it, it practically returns to its original length. It's this natural elasticity that allows a knitted garment to regain its shape after being worn all day, and that makes wool so pleasant to work with on a loom or with needles: it "responds" under the fingers, unlike more inert fibers.

The figures here are quite spectacular: a wool fiber can bend more than 20,000 times before breaking. To put that in perspective, think of all the movements a garment goes through in a single day — sitting down, standing up, bending an arm, stretching a leg — and multiply that by hundreds of days of use. Wool is designed, by its very structure, to endure this cycle without premature fatigue.

For artisans who spin their own wool, this understanding of the cortex also helps in better gauging the twist given to the yarn. A twist that is too loose doesn't fully benefit from this natural elasticity; a twist that is too tight, conversely, can create a rigid yarn that loses some of the desired comfort. Finding the right balance is precisely the art of spinning — knowledge that develops with practice, but which is based on this same biological logic.

It is this same elastic memory that justifies the investment in a quality spinning wheel like the one we use in the workshop: our 24 spindles allow us to precisely control the twist applied to each thread, to respect and fully exploit this natural capacity of the fiber, rather than constraining it.

Source: International Wool Textile Organisation, Wool Notes, Issue 3 (2024); The Woolmark Company, woolmark.com/fibre.