01How spandex is made
Spandex is made by reacting long, flexible polymer chains with stiffer chemical segments to form a block polymer. The flexible parts let the fiber stretch; the stiff parts hold the chains together and pull them back. Most spandex is dry spun: the polymer is dissolved in a solvent, pushed through spinnerets into hot air, the solvent evaporates and the filaments are bundled and wound.
Mills rarely knit or weave bare spandex alone. It is either fed in bare alongside another yarn (common in knits), wrapped in another fiber (covered yarn), or used as the core of a spun yarn with cotton or polyester around it (core-spun, common in stretch denim). The wrap protects the spandex and decides how the fabric feels on the surface.
After knitting or weaving, stretch fabric is heat set on a stenter frame to lock the width and stabilize the spandex. Poor heat setting is a common cause of fabric that grows, curls or shrinks after the first wash.
02Spandex, elastane and Lycra: the naming
They are the same family of fiber. Spandex is the generic name in the US and Canada, and US fiber labeling rules use it. Elastane is the generic name in the EU and most other markets. LYCRA is a trademark of The LYCRA Company, one producer of the fiber, and it also sells specialty versions (for example chlorine-resistant and heat-resistant variants).
Care labels must use the generic name for the market: "spandex" on US labels, "elastane" in the EU. You can only use the Lycra name on labels and hangtags if the fabric uses the branded fiber and you follow the brand’s licensing program.
03Typical spandex percentages by product
| Product | Typical spandex | Why |
|---|---|---|
| Stretch denim and chinos | About 1 to 3% | Comfort and knee movement without losing a woven look |
| T-shirts and polos | About 3 to 5% (or none) | Shape retention and a cleaner fit |
| Underwear and bras | About 5 to 15% | Fit and recovery with soft hand |
| Leggings and sports bras | About 10 to 30% | Compression, support and opacity |
| Swimwear | About 15 to 25% | Fit when wet and stretch recovery |
| Shapewear | About 20 to 40% | Firm compression |
Percentage alone does not tell you how a fabric will feel. A 20% fabric with fine spandex can feel lighter than a 15% fabric with heavy spandex. Specify the spandex denier and the stretch and recovery you want, not just the percentage.
04Pros and cons
- Adds stretch, comfort and freedom of movement to almost any fabric
- Helps garments keep their shape and bounce back after wear
- Enables compression and support in activewear and shapewear
- Small amounts make a big difference, so cost impact can be low
- Works with cotton, nylon, polyester, modal and wool
- Breaks down with chlorine, high heat, oils and sunscreen
- Loses recovery over time, leading to baggy knees and saggy waistbands
- Makes fabrics harder to recycle because blends are hard to separate
- Poor heat setting causes shrinking, growing or curling in the wash
- High-percentage fabrics can feel hot and less breathable
05Typical uses and price
- Leggings, bike shorts and sports bras
- Swimwear
- Stretch jeans and chinos
- Underwear and bras
- Fitted tees, polos and golf trousers
- Waistbands, cuffs and rib trims
- Shapewear and compression garments
Price tier: Mid. Spandex costs more per kilo than polyester or cotton, so fabric price rises with the percentage. Branded and chlorine-resistant versions cost more again. At 2 to 5% the cost impact is small; at 20 to 30% it is a real line item.
06How to spec it with a factory
Stretch problems show up after wear and washing, not in the first sample. Spec stretch and recovery in the tech pack so you have something to test against.
| No. | Field | What to write |
|---|---|---|
| 01 | Fabric composition | Exact percentages using the market’s generic name, e.g. 80% nylon, 20% spandex (elastane in EU) |
| 02 | Spandex yarn | Denier (e.g. 20D, 40D, 70D) and form: bare, covered or core-spun |
| 03 | Fiber brand | Generic or branded (e.g. Lycra); chlorine-resistant variant for swim |
| 04 | Stretch and recovery | Target stretch in length and width and minimum recovery after hold, with test method |
| 05 | Weight | GSM after finishing, with a tolerance such as plus or minus 5% |
| 06 | Heat setting | Fabric to be fully heat set; finished width stated |
| 07 | Shrinkage | Maximum after wash, length and width, with the test method |
| 08 | Testing | Stretch and recovery (ASTM D2594 for low-power knits, D4964 for higher-power elastic and compression fabrics, D3107 for stretch wovens), chlorine fastness for swim |
Certifications and marks
- OEKO-TEX Standard 100
- Tests the finished fabric for harmful substances. Standard request for skin-contact stretch fabric.
- Global Recycled Standard (GRS)
- Only if you claim recycled content in the companion fiber or recycled spandex; ask for transaction certificates.
- bluesign
- Chemical and environmental management at the mill. Common with performance knit suppliers.
From the factory floor
- Wash test the sample five or more times before approving; recovery and shrinkage problems take a few cycles to show.
- For leggings, check opacity stretched (the squat test) in your lightest color.
- For swimwear, ask for chlorine-resistant spandex in writing and test it; standard spandex fails fast in pools.
- Factories sometimes drop the spandex percentage or denier to save cost. Check the composition test on bulk, not just on the sample.
- Keep spandex garments away from hot pressing during production; ask what temperature the factory uses.
07Spandex vs elastic (rubber)
Natural rubber elastic is used in bands and trims and is cheap and strong, but it ages and gets brittle faster and some people react to latex. Spandex is lighter, finer and can be knitted into the fabric itself, which is why it took over in apparel.
08Spandex vs mechanical stretch
Mechanical stretch comes from the yarn or construction, such as textured polyester or a knit structure, with no spandex at all. It gives less stretch and weaker recovery, but it is easier to recycle and less sensitive to heat. Many golf and travel fabrics use it for a little give in a woven.
09Spandex blends: nylon vs polyester base
Nylon and spandex is the premium legging and swim combination: softer, smoother and more abrasion resistant. Polyester and spandex is cheaper, wicks faster and can be sublimation printed. Both work; pick by price and hand feel.
10FAQ
Q01Is spandex the same as elastane and Lycra?
Yes, they are the same type of fiber. Spandex is the US name, elastane is the name used in the EU and most other markets, and Lycra is a brand of it.
Q02How much spandex is in leggings?
Usually about 10 to 30%, blended with nylon or polyester. More spandex gives more compression and support.
Q03Does chlorine ruin spandex?
Yes. Chlorine breaks down standard spandex, which is why pool swimwear goes baggy. Chlorine-resistant spandex variants and PBT-based fabrics last longer in pools.
Q04Can you put spandex in the dryer?
Low heat only, and line drying is better. High heat weakens the fiber and reduces stretch recovery over time.
Q05Is spandex breathable?
Not much on its own. Breathability comes from the companion fiber and the knit; a cotton-rich fabric with a little spandex breathes far better than a high-spandex compression fabric.