What yarn is made of
Yarn is not just a "thread of wool". It is an engineered product — fibres are twisted into singles, singles are twisted into plies, and plies can be further twisted together. Every step affects the properties of the finished yarn — elasticity, strength, texture, and the appearance of the finished object.
Twist
Twist is the spiralling of fibres that holds yarn together. Without twist, the fibres would fall apart. There are two directions of twist:
Z-twist — fibres spiral to the right (clockwise). The diagonal of the fibre follows the middle stroke of the letter Z. The most common direction in commercial yarns.
S-twist — fibres spiral to the left (counter-clockwise). The diagonal follows the middle stroke of the letter S.
When plying, the direction of twist is reversed — if the individual singles have a Z-twist, the plied yarn has an S-twist. This counter-twist plying stabilises the yarn.
Ply — number of strands
Singles (1-ply) — a single twisted strand. Soft but unstable — it tends to bias. Stockinette fabric knitted from singles will slant.
2-ply — two strands plied together. More stable, round cross-section. Stitch definition is good — the knit stitch "V" shapes are crisp.
3-ply — three strands. Round, firm yarn. Traditional for socks and garments.
4-ply and above — progressively rounder and firmer. The term "4-ply" is also used in British terminology as a weight designation (fingering weight), which can be confusing.
How construction affects your work
| Property | Singles / low twist | Plied / higher twist |
|---|---|---|
| Stitch definition | Soft, blurred | Sharp, crisp |
| Pilling | Higher | Lower |
| Durability | Lower | Higher |
| Drape | High | Lower |
| Best for | Shawls, scarves, lightweight garments | Socks, bags, cables |
Practical implications
Cables — require sharp stitch definition. Choose a plied yarn (3-ply, 4-ply) with a pronounced twist. Singles will "swallow" cables.
Lace — singles or 2-ply with low twist. Soft, drapey, and the lace eyelets open up beautifully when blocked.
Socks — firm plied yarn with a nylon content. High twist equals resistance to abrasion.
Stockinette — plied yarn minimises the biasing that singles tend to cause.
