Stretch (extension) is how much a fabric lengthens under a given force. Recovery is how much of that extension it recovers when the force is removed. Growth (unrecovered stretch) is the permanent lengthening that remains. These properties decide how a garment fits, moves and keeps its shape.
Where stretch comes from#
- Knit structure: loops can change shape, so knits stretch without elastane. Rib stretches most in width, then jersey, then interlock.
- Elastane (spandex): adds stretch and strong recovery to both knits and wovens. Even a few percent elastane changes the fabric a great deal.
- Textured yarns: crimped synthetic filaments give some mechanical stretch.
- Woven construction: loose weaves stretch more; stretch wovens usually use elastane in the weft (one-way stretch) or both directions (two-way stretch).
Basic definitions#
Worked example#
A 25.0 cm marked length is stretched to 37.5 cm under the test load. After release and the specified recovery time, it measures 26.0 cm.
- Stretch = (37.5 - 25.0) / 25.0 × 100 = 50%
- Growth = (26.0 - 25.0) / 25.0 × 100 = 4%
- Recovery = (37.5 - 26.0) / (37.5 - 25.0) × 100 = 92%
Testing#
Test methods for stretch and recovery include ASTM D2594 (knitted fabrics with low power stretch), ASTM D3107 (woven fabrics made from stretch yarns) and EN 14704-1 (elastic fabrics, strip test). Each method defines the load, the time held under load, and the recovery time. Results from different methods are not directly comparable. Use the method specified by the buyer.
Garment problems linked to stretch and recovery#
| Problem | Likely link |
|---|---|
| Knees and elbows bagging | High growth; poor recovery |
| Waistband loosening | Elastic or rib losing recovery; heat damage to elastane |
| Garment too tight after washing | Shrinkage combined with low stretch |
| Seams cracking | Seam stretch lower than fabric stretch |
| Neckline flare | Rib stretched during sewing; poor recovery |
Elastane and heat#
Elastane can be damaged by excessive heat in finishing or pressing. Heat-damaged elastane loses recovery, and in severe cases breaks, showing as "grin through" or shiny, broken fibers. Follow the fabric supplier's heat-setting and pressing limits.
Seams in stretch garments#
A seam must stretch at least as much as the fabric in use. Use extensible stitches (overlock, coverstitch, flatlock, zigzag lockstitch) and suitable threads. See stitch types.
Checklist#
- Stretch and recovery requirements agreed with the test method
- Elastane content and type confirmed with the supplier
- Heat-setting and pressing temperatures within the supplier's limits
- Seam stretch checked on the first bulk garments
Practical checks in the factory#
Laboratory tests are the reference, but a few simple checks catch problems early:
- Hand stretch comparison: stretch the bulk fabric and the approved fabric side by side over the same length. A clear difference is a reason to test before cutting.
- Seam stretch check: stretch a sewn seam as far as the fabric goes. If threads crack or stitches pop before the fabric reaches full stretch, the seam is not extensible enough.
- Waistband and cuff recovery: stretch several times and check that the rib or elastic returns to its original length.
- Heat check: after pressing or heat transfer, repeat the recovery check on a test piece to make sure heat has not damaged the elastane.
Related guides#
- Rib fabric: the knit with the highest natural widthwise stretch.
- Single jersey fabric: elastane jersey, the most common stretch knit in apparel.
- Fabric shrinkage: how shrinkage and stretch interact in fit after washing.
- ISO, ASTM and AATCC test methods: the stretch, growth and recovery methods by standard.
- Seam strength: why seams in stretch garments must stretch as much as the fabric.
Frequently asked questions#
Does more elastane always mean better recovery? Not always. Recovery depends on elastane type, content, fabric construction and heat setting. Too much elastane can make a fabric tight and heavy.
Why do stretch jeans grow during wear? Body heat, moisture and repeated stretching cause some growth, especially if recovery is low. Fabrics with better recovery lose less shape.
Can two fabrics with the same stretch percentage feel different? Yes. The force needed to stretch them (the power or modulus) can be very different.