What is elastane (spandex), and why is it added to fabric?
Lycra is the trade name of an elastic polyurethane fibre (its generic name is elastane, spandex in the US). Terms such as "elastane single jersey" and "elastane rib" are well established in the industry; the fibre we are technically referring to is elastane. This is the only class of fibre that can stretch to several times its own length and return to its original length once tension is released. This is precisely what cotton, viscose or polyester cannot provide on their own: controlled, repeatable stretch.
The knit fabric itself is already somewhat stretchy thanks to its loop structure. Elastane increases this stretch in both directions (length and width) and, more importantly, raises the fabric's power to return to shape. Elastane is usually wrapped around the main fibre (covering) or fed into the knit bare/plated; this way the hand of cotton and the movement of elastane are brought together.
Typical elastane content and its effect
In knit fabrics the elastane content is generally in the range of 3–8% by weight. This seemingly small percentage noticeably changes the hand of the fabric:
| Elastane content | Typical character | Common use |
|---|---|---|
| 3–5% | Light stretch, comfortable hand, limited tightness | Everyday T-shirts, bodysuits, basic single jersey |
| 5–8% | Marked stretch, strong recovery, body-hugging feel | Slim fit, underwear, legging-type pieces |
| 8% and above | High compression, strong two-way stretch | Sportswear/performance, swimwear, corset effect |
As the content increases, the GSM (GSM) also tends to rise, because the tensioned elastane gathers the fabric in on itself and the fibre density per unit area increases. That is why the elastane version of the same single jersey typically settles at a higher finished GSM than its greige state.
Stretch and recovery are not the same thing
This is the most commonly confused point. We are talking about two separate properties:
- Stretch (elongation): How far the fabric can extend when stretched. It is expressed with a value such as "50% elongation".
- Recovery: How precisely and quickly the fabric returns to its original dimensions once tension is released. This is what really determines quality.
A fabric that stretches a great deal but does not recover will "bag out" at the knee or elbow, stretch out after washing and suffer permanent deformation. A good elastane fabric is one that, rather than stretching a great deal, can return from however far it stretches. What determines recovery is, more often than not, less about the elastane content and more about correctly fixing the elastane and managing heat during finishing.
Frequently asked questions
What is the typical elastane content in knit fabrics and how does the ratio affect the product?
Elastane content generally ranges from 3–8% by weight. At 3–5% it delivers light stretch and a comfortable hand, used in everyday T-shirts, bodysuits and basic single jersey. At 5–8% it provides pronounced extension and strong recovery, suited to slim-fit garments, lingerie and legging-type pieces. At 8% and above it brings high compression, preferred in sport/performance, swimwear and shapewear-effect products.
What is the difference between stretch and recovery?
Stretch is how far a fabric can extend when pulled, expressed for example as "50% extension." Recovery is how accurately and quickly the fabric returns to its original dimensions once tension is released, and this is what truly defines quality. A fabric that stretches a lot but does not recover bags out at the knees and elbows and undergoes permanent deformation. A good fabric is one that can return by as much as it has stretched.
Why does single jersey with spandex settle at a higher weight than its greige state?
As the ratio increases, the weight (GSM) also tends to rise, because the tensioned elastane draws the fabric in on itself and the fibre density per unit area increases. For this reason the spandex version of the same single jersey typically settles at a higher finished weight than its greige state. The exact target weight is determined at the sampling stage according to fabric construction and end use.
How is shrinkage and dimensional stability secured in spandex fabric?
Dimensional stability runs through the production steps. Heat setting fixes the elastane at a controlled temperature, minimising post-production relaxation; sanforising/compacting consumes the shrinkage allowance during processing to lower in-use shrinkage; setting at the correct width and weight stabilises the finished goods to the target dimensions. Dimensional change after washing is typically accepted within a single-digit percentage band; the exact target is set on the sample.
Why do spandex fabrics require special attention in the dye house?
Elastane is a far more heat-sensitive fibre than cotton. Excessive temperature yellows the elastane and permanently weakens its stretch and recovery; that is why temperature in the drying, setting and pressing steps is adjusted to the spandex. Moreover, the reactive dye used on cotton does not take on elastane, so colour is assessed across the blend as a whole and, where necessary, a separate dyeing strategy is established for the elastane.
In which products is spandex knit fabric essential?
The value of spandex knit emerges in products that hug the body and work with movement. In sport and performance, freedom of movement together with return to shape is essential; lingerie and bodysuits must sit against the skin and hold their shape all day; in slim-fit fashion, keeping the pattern from dropping depends on the elastane; at cuffs, collars and gathered areas, stretch and recovery are needed together.
Dimensional stability and shrinkage
Shrinkage in knit fabrics (especially length shrinkage after the first wash) is a natural phenomenon; elastane complicates this equation. Elastane knitted under tension can gather the fabric in when it relaxes with heat and washing, leading to dimensional drift. Securing dimensional stability runs through the production steps:
- Heat setting: Stabilising the elastane at a controlled temperature to minimise post-production relaxation.
- Sanforising / compacting finish: "Using up" the shrinkage allowance during production to reduce shrinkage in use.
- Setting at the correct width and GSM: Stabilising the finished fabric to the target dimensions.
In the industry, dimensional change after washing in knit fabrics is typically accepted within a certain tolerance band (usually single-digit percentages); the exact target value is determined at the sampling stage according to the fabric construction and end use.
What to watch out for when dyeing and finishing elastane fabrics
Elastane is a far more heat-sensitive fibre than cotton. This is the fundamental reason why elastane knit fabrics require special attention in the dyehouse and on the finishing line:
- Heat control: Excessive temperature yellows the elastane and permanently weakens its stretch and recovery. In the drying, setting and pressing steps, the temperature is adjusted to suit the elastane.
- Pre-treatment: Uncontrolled pre-treatment can damage the elastane in elastane fabrics; pre-treatment is planned to protect the fibre.
- Dye selection: While reactive dyeing is used for cotton, elastane will not hold this dye; for this reason colour is evaluated across the blend as a whole, and where necessary a separate dyeing strategy is set up for the elastane.
- Colour consistency: On a stretching surface, colour difference becomes more noticeable under tension; working to a tight batch tolerance (a measurable colour difference, ΔE) becomes critical.
End use: where is elastane essential?
The real value of elastane knit fabrics emerges in products that fit the body and work with movement:
- Sport and performance: Freedom of movement and return to shape are essential.
- Underwear and bodysuits: Pieces that sit close to the skin and must hold their shape all day.
- Slim-fit fashion: Body-hugging T-shirts, dresses, leggings; keeping the fit from "dropping" depends on the elastane.
- Cuffs, collars and gathered areas: Stretch and recovery are required together.
To explore in more depth which knit family suits which use, and the differences between stretchy structures such as 1×1 rib and 2×2 rib, see our knit fabric guide; for the distinction between ribbed structures, see the differences between 2×2 rib and 1×1 rib; and for the full portfolio and GSM ranges, take a look at our fabrics page.
With KARCEM
In elastane fabric, the result is determined less by the elastane content than by how it is fixed and how heat is managed in dyeing. At KARCEM we knit on our own machines and coordinate dyeing, printing and finishing through our vetted contract network with a single point of contact; this way the thermal behaviour of the elastane, its shrinkage allowance and its recovery are tuned under one coordinated specification. On the colour side we verify within-batch and batch-to-batch consistency against a ΔE<1 target on the incoming lot, confirm recovery and dimensional stability with physical samples throughout the sample→approval→production process, and with our commission (CMT) capacity we develop to the required composition and GSM. For an elastane single jersey, a rib or a custom-ratio blend, send us your sample and quotation request; let us determine the right elastane content and finish combination together.