Fibres · Synthetic
Elastane / Spandex
The elastic core of yarns: a single strand, added in a blend, gives fit and recovery to swimwear, leggings and cuffs. It is almost never worked on its own, but a few per cent are enough to change the behaviour of the whole fabric.
Translated from Italian. A native knitter has not reviewed this translation yet.
History
It was born in 1958 in the DuPont laboratories, where the chemist Joseph Shivers developed a polyurethane fibre able to stretch and spring back like rubber, but lighter and stronger. It reached the market under the Lycra brand, while in the United States the generic name spandex (an anagram of "expands") took hold, and in Europe elastane. Within a few decades it transformed sportswear, underwear and modern corsetry.
How the yarn is made
It is an entirely synthetic fibre, a segmented polyurethane made by chemical reaction from petroleum. The polymer is extruded into continuous filaments, usually by dry spinning, in which the solvent evaporates and leaves the elastic yarn. It is rarely used bare: it is almost always covered or twisted with another fibre (core-spun), so that the elastic core stays hidden in the centre and only the wool, cotton or companion fibre shows on the surface.
Why it is prized
Its value is not aesthetic but functional: no other fibre gives back such extreme elastic memory. It can stretch to several times its length and return precisely to its original shape, without giving or bagging. Even in a minimal blend it turns a rigid fabric into a garment that follows the body, fits close and does not bag at the elbows and knees. It is the ingredient that keeps ribs, cuffs and technical garments in shape.
Dyeing
It is a difficult fibre to dye and yellows over time. For this very reason, in practice it is hardly dyed at all: buried in the centre of a covered yarn, it stays invisible, and the outer fibre wrapped around it takes the colour. When it does need dyeing, disperse or acid dyes are used, with lower fastness than natural fibres.
Care
It fears chlorine, heat and time: bleach degrades it quickly, water that is too hot and the tumble dryer make it lose its elastic recovery, and over the years it tends to yellow and relax. Wash it in lukewarm water with a neutral detergent, without harsh softeners, and air-dry it away from heat. Treated well, it keeps its fit for a long time.
End of life
This is the weak point of the fibre: it is not biodegradable and comes from petroleum. Recycling is complicated by the fact that it always lives in blends with other fibres that are hard to separate, so garments containing it rarely enter textile recycling streams. The first partly renewable or recycled elastanes exist, but they are still a niche.
How to recognise it
| Hand | On its own it is an elastic, rubbery fibre, smooth and rather cool to the touch. In a yarn it is recognised more by its behaviour than by its handle: the yarn "springs" and stretches with a soft resistance that then brings it back. |
|---|---|
| Look | The bare strand is thin, glossy and transparent. In a blend it is almost invisible, because it stays at the centre of the covered yarn: you sense its presence from the way the fabric stays taut and compact without giving. |
| Behaviour | Extreme, immediate elastic recovery: pull it and it snaps back with no give and no halo. It holds no appreciable warmth, and its role lies entirely in fit and shape recovery, not in thermal comfort. |
| Burn test | Synthetic signature: in the flame it melts and shrinks back instead of burning cleanly, with a sweetish chemical smell, and leaves a sticky residue that hardens into a dark bead. It does not self-extinguish as cleanly as protein fibres. |
| Home tests | Stretch test: pull and release, it snaps back to its original shape without staying deformed · Burn test: melts and shrinks away, sweetish chemical smell, sticky then hard residue · Bare strand test: if the yarn is covered, pulling away the outer fibres reveals a glossy elastic strand at the centre |
| Confused with | Natural rubber or latex, which however yellow and dry out sooner and feel stickier · Other stretch yarns, where the work is still done by a hidden elastane core |
| Only in a lab | Telling elastane apart from other elastomers and measuring its exact percentage in a blend requires chemical laboratory analysis (ISO 1833), because by eye you can only detect its presence, not its amount. |
Physical facts
| Property | Value | Source |
|---|---|---|
| elastic memory | Extreme | research |
| sag | None | research |
| halo | None | research |
| felting risk | None | research |
| fineness (µm) | — | research |
| moisture regain (%) | 1.2 | research |
| typical shrinkage (%) | 3–8 | estimate |
| staple length (mm) | — | research |
measured = a measurement with a reference · iso = a standard · research = a verified source · estimate = plausibility only
Good for
stretchy, close-fitting knitwear · ribs and cuffs that keep their shape · swimwear and sportswear · leggings and underwear · garments that must follow the body
Less good for
garments with a soft, fluid drape · yarns to be used pure · projects meant to last decades · garments exposed to chlorine and strong heat