“Chlorine resistant” on a swimsuit hangtag can mean two very different things: the colour survives pool water, or the stretch does. Most test reports only prove the first. This guide explains what each test measures, how to read a report, and what to require before bulk.
ISO 105-E03 grades colour change in chlorinated water. Elastane loss — the sag and see-through — needs a separate tensile-retention test.
E03 results are only comparable at the same active-chlorine level. The report must state it.
AquaForm™ 220: Intertek GZHT03093360 — chlorinated-water fastness grade 4, UPF 50+, 30,000+ Martindale rubs.
The same report shows AquaForm™ is not bleach-fast (spot test ~3.5). Care labels must say so.
What chlorine actually does to swimwear
Chlorine is an oxidiser. In a nylon/elastane swimsuit it attacks on two fronts. It fades or shifts dyes, especially bright and dark shades. And it breaks down elastane (polyurethane), so the fabric loses power, the seat and straps sag, and a stretched area can turn sheer. Sunscreen, body oils and the heat of hot tubs accelerate both.
Colour damage is visible in a lab test within hours. Elastane damage builds up over many swims — which is why a swimsuit can pass a colour test and still be “worn out” in a season of training.
The tests that matter for swim fabric
| Test | Measures | Why it matters |
|---|---|---|
| ISO 105-E03 (chlorinated water) | Colour change after exposure to chlorinated water, graded 1–5 on the grey scale | Pool colourfastness — the headline “chlorine” result |
| AATCC TM162 | Colourfastness to chlorinated pool water (US method) | Often requested by US retailers instead of E03 |
| Elastane retention after chlorine | Tensile or elongation properties before and after repeated chlorine exposure | The real “chlorine resistant” question for training swimwear; no single universal method — agree it with your lab |
| ISO 105-E02 (sea water) | Colour change in salt water | Beach and resort programmes |
| ISO 105-B02 (artificial light) | Light fastness under xenon arc | Fading on sun loungers and in shop windows |
| AATCC TM183 / AS/NZS 4399 / EN 13758-1 | UV transmission and UPF rating | Any UPF claim on the label |
| ISO 105-E04 / ISO 105-X12 | Perspiration and rubbing fastness | Colour transfer onto loungers, towels and light trims |
How to read a chlorine test report
- Grade. 5 means no change, 1 severe change. Grade 4 is a common commercial target for pool colourfastness — confirm against your own brand manual.
- Concentration. ISO 105-E03 can be run at different active-chlorine levels. A grade at a low concentration does not equal the same grade at a high one. Ask which level was used.
- Shade. A report covers the colour tested. A navy pass does not certify a fluorescent pink on the same base.
- What is not in it. A colourfastness report says nothing about elastane retention unless that test is listed.
Our AquaForm™ report — what it proves, and what it doesn’t
| Item | Result on file |
|---|---|
| Fabric | AquaForm™ 220 — 75% nylon / 25% Lycra®, 220 g/m² |
| Laboratory / report | Intertek Guangzhou · GZHT03093360 · 2026 |
| Chlorinated water | Grade 4 · ISO 105-E03 |
| UV protection | UPF 50+ · AATCC TM183 · ~99.95% UV blocked |
| Abrasion | 30,000+ Martindale rubs |
| Household bleach | Not bleach-fast (spot test ~3.5) |
This report supports a pool-colourfastness and UPF claim for AquaForm™ in the tested shade. It is not an elastane-retention test, and it shows the fabric is not bleach-fast — so “do not bleach” belongs on the care label. Nylon/elastane swim like AquaForm™ suits fashion and resort swimwear; for daily lap training, PBT or polyester-rich chlorine-resistant constructions last longer, and we will say so at brief stage.
Choosing a swim construction by use
| Use | Typical construction | Test focus |
|---|---|---|
| Fashion / resort swim | Nylon / elastane (e.g. AquaForm™) | Colour (E03, E02, B02), UPF, opacity of light shades |
| Frequent pool use | Chlorine-resistant elastane grades, PBT blends | Elastane retention after chlorine, colour |
| Competitive training | Polyester-rich or 100% polyester | Durability over many hours, colour |
- Colourfastness to chlorinated water ISO 105-E03 at [x] mg/l active chlorine: grade ≥ [4] per colour
- Sea water ISO 105-E02 and light ISO 105-B02: grades as per brand manual
- UPF claim: AATCC TM183 or AS/NZS 4399 report per base; claim only the tested rating
- Elastane retention after chlorine: method and limit agreed on approved sample
- Care label to reflect bleach result; reports attached per dye lot
Swim bulk typically runs 30–40 days after PPS. For lining and cups, see swimwear lining construction; for recycled claims, recycled swimwear and GRS TC.
Methods and sources cited
- ISO 105-E03 — colourfastness to chlorinated water (swimming-bath water)
- AATCC TM162 — colourfastness to water: chlorinated pool
- ISO 105-E02, ISO 105-B02, ISO 105-E04, ISO 105-X12
- AATCC TM183, AS/NZS 4399, EN 13758-1 — UV protection
- Intertek report GZHT03093360 (AquaForm™ 220) — summary on /resources/fabric-tests
Standards are named as the methods buyers commonly specify. Factory results are only those stated as on file; programme results are reported per brief.