Superwash Wool vs Non-Superwash — What's the Difference?
If you've spent any time in a yarn shop or browsing online, you've seen "superwash" on labels and wondered whether it matters. It does — especially for socks, baby items, and anything you knit to a precise fit. Here's exactly what the difference is and when it matters for your projects.
What "Superwash" Actually Means
Wool fibres have a microscopic scale structure on their surface — similar to fish scales, pointing toward the tip. When these scales get wet and agitated (like in a washing machine), they lock together and the fibres felt: the yarn shrinks, mats, and becomes dense and thick. This is usually irreversible.
The superwash treatment removes or coats these scales so they can't interlock. The result is wool that won't felt in a hot wash or tumble dryer. Most superwash treatments either chemically strip the scales (chlorination) or coat the fibre in a polymer resin.
The Tradeoffs of Superwash Wool
Machine-washable wool sounds ideal — but the superwash treatment changes how the yarn behaves in ways that matter to knitters:
It Grows More After Washing
The scale structure is part of what gives wool its elasticity and memory. Superwash wool, especially wool treated with resin coating, tends to grow significantly in length after washing — sometimes 5–10%. A sweater that fits before washing can become noticeably longer and droopier after. This is particularly pronounced in drop-shoulder constructions and long items like cardigans.
It Has Less Memory
Regular wool stretches and bounces back. Superwash wool, especially resin-treated versions, holds stretch longer and recovers more slowly. Socks knitted in superwash sometimes feel slightly baggy by the end of the day. Non-superwash socks hold their shape better.
It Has Different Stitch Definition
The smoother surface of superwash yarn means stitches slide against each other more freely. This gives a slightly softer hand feel but less crisp stitch definition — cables and textured patterns look slightly less sharp compared to the same pattern in non-superwash wool.
It Feels Different
Many knitters describe superwash wool as feeling slightly "squishier" or more plastic-like than untreated wool. Some find this nicer; some find it off-putting. It's a personal preference, but worth touching both before committing to a large project.
Non-Superwash Wool — the Other Side
Non-superwash wool has its own list of properties that make it better for specific applications:
- Better stitch definition: Cables, lace, and textured stitches look crisper.
- More elasticity: Returns to shape quickly after stretching.
- Holds its size after washing: Garments maintain their dimensions when blocked correctly (cold water soak, squeeze, pin to shape).
- Felts if abused: Hot wash or aggressive machine agitation will felt it. This is a feature when you want it (see intentional felting) and a disaster when you don't.
When to Choose Superwash
- Socks: Socks need frequent washing. Superwash sock yarn is the practical choice unless you're happy with hand-washing.
- Baby and children's items: Parents machine-wash everything. Superwash is almost mandatory for baby gifts.
- Gifts for non-knitters: If the recipient doesn't know about hand-washing wool, superwash saves the item from accidental felting.
- Items that must be machine-washable: Anything going to a household without time for hand-washing.
When to Choose Non-Superwash
- Fitted sweaters and garments: Non-superwash holds its shape and dimensions better. Superwash sweaters can grow and drop over time.
- Colorwork: Non-superwash gives better stitch definition and colour contrast in Fair Isle and stranded colourwork.
- Cabled projects: Cables look sharper and more three-dimensional in non-superwash wool.
- Projects where you want the option to felt later: Only non-superwash felts.
How to Tell on a Label
Look for:
- The word "superwash" explicitly stated
- A washing machine symbol (filled bucket with a number inside) — this typically indicates superwash
- The word "machine washable"
If the label shows a hand symbol (hand-wash only) or a strikethrough washing machine, the yarn is not superwash. Treat it as non-superwash regardless of what the fibre is.
When in doubt, hand-wash and lay flat to dry. This is safe for all wool and wool blends, superwash or not.
Unsure which type of wool fits your project? Ask Emma for a specific recommendation →