Fibres · Animal
Superwash Wool (Treated)
The easy everyday wool: machine washable, soft and even, with no risk of felting. The other side of the coin is that it tends to grow and lengthen in the wash, so lengths need to be kept in check.
Translated from Italian. A native knitter has not reviewed this translation yet.
History
It is real wool made washable by a treatment developed in the mid-twentieth century and refined in the 1960s and 1970s: the Hercosett process partly removes the fibre's scales with chlorine and coats them with a thin polymer resin. From there came the generation of "machine washable" and "superwash" yarns, now standard for socks, children's garments and everyday knitwear, often on a worsted merino base.
How the yarn is made
It starts from the same shorn and combed wool as always, usually a fine, even merino. The fibre is then treated in a continuous process: an oxidising step that smooths down the scales and the deposition of a polymer film that seals them. The result is a yarn that is smoother, more even and slightly more lustrous than untreated wool, and glides well on the needles.
Why it is prized
It combines the warmth and breathability of wool with the convenience of machine washing. With the scales neutralised the fibres no longer catch on each other, so the garment does not felt and colours stay bright and crisp: it is the ideal choice when you need durability and easy care, from socks to baby garments.
Dyeing
Excellent, often better than untreated wool. Keratin fixes acid dyes fast, and the smooth surface lets colour penetrate evenly: shades come out saturated, vivid and even, which is why superwash is the hand dyers' favourite for gradients and semi-solids.
Care
Machine washable on a wool or delicate cycle, in cold water with a neutral detergent. It does not felt, but the sealed surface makes it slippery and prone to stretching out: always dry it flat and never hang it wet, because under the weight of the water it lengthens and never comes back. Pilling is limited if the yarn has medium twist.
End of life
The polymer coating and the residues of the chlorine treatment compromise its biodegradability and make mechanical recycling harder than for untreated wool. It is still a protein-based fibre, but less "circular" than untreated wool: the most sustainable choice is to make it last a long time.
How to recognise it
| Hand | Soft, warm and even, but smoother and more slippery than untreated wool: the coating dampens the fibre's natural friction. |
|---|---|
| Look | Slightly more lustrous and even than untreated wool, with less pronounced crimp because the yarn is compacted and sealed. |
| Behaviour | Springy but with a somewhat lazier recovery than untreated merino: under tension or when wet it tends to give and lengthen, and it holds warmth well. |
| Burn test | Protein signature like any wool: burns slowly and self-extinguishes, smells of burning hair, and leaves a small black, crumbly bead. The thin polymer film is not enough to make it melt like a synthetic. |
| Home tests | Burn test: slow flame, goes out by itself, smell of burning hair · Wash test: agitated with heat it does not felt, whereas untreated wool does · Wet stretch test: it gives and lengthens, a sign of the growth typical of superwash |
| Confused with | Untreated merino: same hand when dry, but the untreated one felts and this one does not · Washable wool-acrylic blends: but acrylic melts into a hard bead in the flame and feels cold to the touch |
| Only in a lab | Confirming the presence and type of surface treatment (Hercosett resin, descaling) requires laboratory microscopy and analysis; to the naked eye it can only be told by indirect clues. |
Physical facts
| Property | Value | Source |
|---|---|---|
| elastic memory | Medium | research |
| sag | High (tends to grow in the wash) | research |
| halo | Low | research |
| felting risk | None | research |
| fineness (µm) | 17–24 | research |
| moisture regain (%) | 16.0 | research |
| typical shrinkage (%) | 0–3 | estimate |
| staple length (mm) | 60–100 | research |
measured = a measurement with a reference · iso = a standard · research = a verified source · estimate = plausibility only
Good for
washable socks · children's garments · everyday knitwear · intense colours and hand dyeing · knitters who want easy care
Less good for
very long or heavy garments (they grow in length) · ribs that need to stay compact over time · maximum warmth for the weight compared with untreated wool