Stretch sells the first try-on. Recovery decides the review three weeks later — baggy knees, a waistband that grows, a seat that sags. This guide explains how recovery is actually tested, which numbers to record, and how to write it into a purchase order so bulk behaves like the sample.
Elongation (how far it stretches at a set force) and recovery or growth (how much it comes back). “Four-way stretch” is neither.
Cyclic strip tests (EN 14704-1 / ISO 20932-1) and hold-and-relax growth tests (ASTM D2594) answer different questions.
Heat-setting, washing and dyeing change recovery. Approve on finished, washed fabric — not greige.
A strip test cannot see the seat of a squatting wearer. Confirm on a garment proto.
Stretch, recovery and growth — three different words
Elongation is how far fabric extends under a defined force, measured warp-wise (length) and weft-wise (width). Recovery is the share of that extension the fabric gives back when the force is removed. Growth (or residual extension) is what it does not give back — the permanent length that turns into baggy knees.
A fabric can stretch generously and recover poorly. That is the fabric behind most “lost its shape” returns. When a supplier says “four-way stretch”, ask for elongation and recovery figures and the method they were measured by.
The test methods buyers actually specify
| Method | What it does | What it tells you |
|---|---|---|
| EN 14704-1 / ISO 20932-1 (strip test) | Cycles a fabric strip to a set elongation or force several times on a tensile tester | Elongation, modulus (power) and recovery after repeated stretching — closest to wear |
| ASTM D2594 | Stretch and growth of knitted fabrics with low power, including a hold-and-relax growth measurement | How much permanent growth remains after the fabric is held stretched |
| ASTM D4964 | Tension and elongation of elastic fabrics on a constant-rate-of-extension tester | Load–elongation curve; useful for high-power compression fabrics and bands |
For leggings and bras, the cyclic strip test is the most informative because it imitates repeated movement. A growth test is the better tool when the complaint is “it gets longer over a day of wear”.
What to record — and how to read it
- Both directions. Knits behave differently lengthwise and widthwise. Leggings usually load the width across the seat and the length through the knee.
- Elongation at a fixed force. Tells you how “easy” the fabric feels on, and whether the size chart needs adjusting.
- Recovery after cycling. The headline number for shape retention.
- Modulus (power). How firmly it holds the body — the difference between a second-skin and a sculpting hand.
- Before and after washing. If recovery drops sharply after a home-laundering cycle, the elastane or the heat-setting is the suspect.
Pass/fail limits are a brand decision. Agree them with your lab and write them on the PO as numbers tied to the method — not as “excellent recovery”.
What drives recovery in the fabric
| Lever | Effect on recovery |
|---|---|
| Elastane content | Most performance leggings bases sit around 15–25% elastane. ZIESHINE named bases: PowerForm™ 19% Lycra®, AirTouch™ 20% spandex, AquaForm™ 25% Lycra®. |
| Elastane quality | Branded and premium elastane grades hold recovery better through heat-setting, washing, chlorine and sunscreen. |
| Hard yarn | Nylon 66 tends to hold shape under heat better than commodity nylon 6 — see nylon 66 vs nylon 6. |
| Knit structure | Double knits and interlocks recover more evenly than light single jersey; warp knits behave differently again. |
| Heat-setting | Too hot or too long damages elastane; too little leaves the fabric unstable. Ask the mill for the setting window, not just the result. |
Confirming recovery on the garment
Lab strips are stretched evenly. A body is not: the seat, knee and waistband take far more strain than a strip does, and seams concentrate it. Before PPS, we judge recovery on the proto itself — after wear-movement (squats, lunges, sitting) and again after washing — and compare knee and seat against the unworn garment.
Recovery and opacity fail together: an overstretched seat shows through and stays stretched. Pair this guide with how we evaluate squat-proof fabrics and choose weight with best GSM for leggings.
- Method: EN 14704-1 / ISO 20932-1, [n] cycles to [x]% elongation, length and width
- Recovery and residual extension: within the limits approved on the sample fabric
- Tested on finished fabric after [n] home-laundering cycles (ISO 6330, programme [x])
- Bulk fabric re-tested per dye lot or per [x] m; results attached to shipment
How ZIESHINE handles it
Our named yoga and sport bases pass an in-house four-way stretch gate before garment sampling, and PowerForm™ is built on a nylon 66 / Lycra® stack chosen for shape retention. Programme-specific lab tests are quoted on the brief; we do not publish recovery numbers we have not had tested on your fabric and colour.
Lock the hand on yoga fabrics, then take the programme to the leggings manufacturer desk.
Methods and sources cited
- EN 14704-1:2005 / ISO 20932-1:2018 — elasticity of fabrics, strip tests
- ASTM D2594 — stretch properties of knitted fabrics having low power
- ASTM D4964 — tension and elongation of elastic fabrics
- ISO 6330 — domestic washing and drying procedures
Standards are named as the methods buyers commonly specify. Factory results are only those stated as on file; programme results are reported per brief.