Wool yarn

From sheep fleece to knitting yarn

Wool is a protein fibre made mainly from keratin. Sheep grow a fleece that is shorn, sorted and washed before further processing. Washing the raw fleece, known as scouring, removes dirt and much of its wool grease. The clean fibres then follow different preparation and spinning routes.

Woollen processing generally produces an airy yarn with fibres arranged less uniformly. Worsted processing aligns and combs the fibres for a smoother result. These are manufacturing terms: a worsted-spun yarn is not necessarily the thickness called worsted weight. That distinction is useful when a pattern depends on the loft or surface of a particular yarn.

What wool contributes to a project

The fibre's crimp helps trap air and contributes to elasticity, while its internal structure can absorb water vapour. The resulting fabric still depends on stitch density and construction. A tightly worked mitten and an open lace shawl will not offer the same warmth simply because both contain wool.

Wool also has surface scales associated with felting. Shrink-resistant treatments change that behaviour, so superwash and untreated yarns deserve separate attention. When choosing a substitute, compare the original yarn's preparation, twist and care instructions alongside gauge. Wash the sample before measuring it, and check how it behaves when stretched and released. Matching the label's wool percentage is a starting point; matching the fabric is what makes the replacement useful.