Yarn Ply and Twist Explained

The two variables

Ply: how many strands

Fiber is first spun into a single strand - a single. Two or more singles twisted together make a plied yarn: a 2-ply, 3-ply, 4-ply and so on. Untwist the end of any yarn and you can count them.

Plying does two things. It balances the twist, so the yarn does not corkscrew, and it makes the yarn rounder in cross-section. More plies means a rounder yarn.

Twist: how tight

Twist is what holds fibers together at all. Too little and the yarn falls apart; too much and it becomes wiry and starts to kink back on itself.

Between those extremes is a wide usable range, and where a yarn sits in it is a deliberate design decision by the spinner. It is the single most under-discussed property in yarn buying.

What ply and twist actually predict

Read that table twice and most of the yarn advice on this site falls out of it. The reason our amigurumi picks are firmly plied cottons, and our shawl picks are softer, is this variable rather than the fiber.

Why your yarn splits

Splitting is when the hook or needle goes between the plies instead of under the whole strand, leaving a half-stitch that unravels later.

It has two causes and one of them is not your fault.

1. Loose twist or a single. There is nothing holding the fibers together for the tip to catch, so it goes through them. This is construction, not technique.
2. A blunt or badly-shaped tip. A tip that is pushed rather than guided finds the gap between plies. See in-line vs tapered crochet hooks - a tapered throat gathers the strand and splits less.

If a yarn splits constantly, changing the hook helps and changing the yarn helps more.

Why your yarn pills

Pilling is short fiber ends working their way to the surface under friction and tangling into a ball. Three construction factors drive it.

• Fiber length. Short fibers have more ends per inch of yarn. This is why linen barely pills and why merino pills more than a coarser wool.
• Twist. A tight twist physically traps the ends. A loose one lets them wander.
• Spinning method. Worsted-spun yarn - fibers combed parallel before spinning - has far fewer ends sticking out than woolen-spun yarn, where fibers lie in every direction.

That is why an anti-pilling claim on a ball band is a construction claim rather than a fiber one. Our why yarn pills page covers the mechanism in full.

Worsted-spun and woolen-spun, which is a different thing again

This is a genuine source of confusion because the word worsted is used for two unrelated ideas.

• Worsted weight is a yarn thickness - category 4 in the Craft Yarn Council system.
• Worsted-spun is a preparation method: fibers combed parallel, short ones removed, then spun. It makes a smooth, dense, strong, hard-wearing yarn.
• Woolen-spun is the opposite: fibers carded in all directions and spun with air trapped in. It makes a light, lofty, warm yarn that pills more and wears faster.

A yarn can be worsted weight and woolen-spun, or fingering weight and worsted-spun. The two words are unrelated and the ball band will usually tell you neither.

How to judge a yarn in your hand

None of this is printed on the label, so here is what to do with a ball in a shop.

1. Untwist the end. Count the plies. Three or four is firm; one is a single.
2. Untwist a few inches and let go. A firm twist springs back sharply. A loose one barely moves.
3. Rub a length between your palms hard, ten times. If it fuzzes visibly, it will pill.
4. Hold it to the light. A halo of loose fibers means woolen-spun and a softer, warmer, more pill-prone yarn.
5. Pull it firmly. A yarn that drifts apart under moderate tension is undertwisted for hard-wearing use.

None of this makes a yarn bad

A softly spun single is the wrong yarn for a sock and exactly the right yarn for a cowl worn next to the neck. A hard-twisted 4-ply is the wrong yarn for a halo-bloomed shawl and exactly right for a hard-wearing sweater.

The point of knowing about ply and twist is not to grade yarns. It is to stop being surprised - by the amigurumi that would not hold its shape, by the sweater that pilled after a month, by the yarn that split on every stitch.