Cotton yarn: properties, finishing and what it's good for
What do mercerised, singed or combed mean on the label, and how does cotton actually behave on the needles?
How cotton behaves when you knit it
| Property | Cotton | Compared to wool |
|---|---|---|
| Warmth | Cooling, breathable | Wool insulates and warms |
| Stretch | None. Stitches don’t spring back | Wool springs back |
| Weight | Denser and heavier per metre | Lighter, more lofty |
| Care | Usually machine wash 30–40 °C | Often hand wash cold, can felt |
| Shape stability | Doesn’t felt, but stretches with wear | Holds shape better, can felt |
| Behaviour on the needles | Glides well, smooth versions can split | More grip, rarely splits |
All values are guidelines, the yarn label is always the most reliable source.
Mercerised, singed, combed: what the finishing terms mean
Many cotton labels carry extras like mercerised, singed or combed. These aren't marketing terms but real finishing steps that change the sheen, smoothness and quality of the yarn. Premium yarns are often finished in more than one way (combed and mercerised, for example).
| Term | What happens in the process | Effect on the yarn | How to spot it on the label |
|---|---|---|---|
| Mercerised | Treated under tension with caustic soda. The fibres swell and become rounder in cross-section. | Permanent sheen, smoother surface, more tensile strength, richer colours. Slightly less absorbent. | "mercerised", "mercerized", "merc." |
| Singed (gassed) | Briefly passed through a gas flame. The fibre ends sticking out of the strand burn off. | Smooth, clean surface, barely any pilling, a subtle sheen, with no chemical treatment. | "singed", "gassed" |
| Combed | Short fibres are combed out of the sliver before spinning. Only long, parallel fibres remain. | Very even, smooth, knot-free, premium quality and durable. | "combed", "combed cotton" |
All values are guidelines, the yarn label is always the most reliable source.
Does cotton really stretch out?
A little, yes. Cotton fibres don't spring back the way wool does, so stretched stitches stay stretched. On a dishcloth you won't notice; on a heavy jumper you will, because the garment's own weight slowly pulls the fabric out of shape.
What helps:
- Pick yarns with a small elastane content (3–5 %), the ribbing will hold tension.
- Knit a touch tighter than usual, half a needle size down is often enough.
- Dry flat, never hang. Wet weight will stretch the piece otherwise.
- For fitted shapes, reach for a cotton blend with linen, viscose or polyamide.
Where cotton works well, and where it doesn't
Cotton is the first choice for anything that needs to be cool, light and easy-care: relaxed summer jumpers and tops, beach wraps, baby clothes, dishcloths and tea towels, amigurumi (especially mercerised, because it holds its shape) and fine summer shawls with drape.
It's less ideal for very fitted garments, heavy winter wear (it doesn't warm enough) and classic socks (too inelastic, wears through quickly). For those, reach for wool or a cotton blend with elastane.
Substituting wool with cotton
Want to knit a pattern that calls for wool in cotton instead? Often works, just keep a few points in mind:
- Run length: stay within ±20 % of the original yarn, otherwise the quantity guidance won't hold.
- Gauge swatch: cotton tends to come out a bit denser. Knit a swatch, wash, dry, then measure, not straight off the needles.
- Pattern choice: relaxed oversize jumpers and shawls work, fitted shapes and long cardigans will sag.
- Plan for the weight: a cotton version of the same garment will weigh noticeably more than the wool original.
Looking for a substitute for a specific project?
→ Find a yarn substituteFrequently Asked Questions
What is mercerised cotton?
Mercerised cotton has been treated under tension with caustic soda. The fibres swell, become rounder in cross-section, and the surface ends up smoother. The result is a permanent silky sheen, more tensile strength, and richer colours, because the smoother fibre takes in light and dye pigments more evenly.
What's the difference between mercerised and regular cotton?
Regular cotton is matte, softer and a bit more absorbent. Mercerised cotton has a lustrous sheen, holds its shape better and is more tear-resistant, but slightly less absorbent. On the needles, mercerised cotton glides faster but can split more easily. Perfect for amigurumi, doilies or fine summer pieces. For absorbent dishcloths, stick with untreated.
What does singed (gasiert) mean on a yarn label?
Singed (also called "gassed") means the yarn has been briefly passed through a gas flame to burn off the loose fibre ends sticking out from the strand. The yarn becomes smoother, pills less and gets a subtle sheen, without any chemical treatment. High-quality cotton yarns are often both singed and mercerised.
What is combed cotton?
Combing removes the short fibres from the sliver before spinning, leaving only the long, parallel fibres. The result is an unusually even, smooth, knot-free yarn, often labelled as "combed cotton". It's higher quality and more durable than uncombed (carded) cotton.
Does cotton really stretch out?
Pure cotton does grow a little as you wear it, because the fibres lack the springiness wool has. On large, heavy pieces (a jumper) it's noticeable; on smaller pieces, barely. The fixes: a small percentage of elastane in the blend, knit a touch tighter than usual, and always dry flat so the weight of the wet garment doesn't pull it out of shape.
Can I substitute cotton for wool?
Yes, if the pattern allows it. Relaxed jumpers, shawls and summer pieces work well. On fitted pieces or ribbed cuffs you'll notice the missing stretch. When swapping, keep run length within ±20 %, knit a new swatch (cotton often comes out a bit denser), and plan for the extra weight, a cotton version of a jumper weighs noticeably more than the wool original.