Buyers argue about composition more than about any other figure in swimwear fabric, and they usually argue about the wrong part of it: the number itself rather than the tolerance behind it.
What composition actually controls in swimwear fabric
Nylon feels better and dyes deeper; polyester survives chlorine and price pressure better.
The consequence is that this figure sets the floor for everything downstream: the process, the price and the failure mode all follow from it.
For Swimwear fabric, the working range is 80/20 or 78/22 nylon/spandex; polyester/spandex. Inside that band the choice is commercial; outside it, the product changes category and so does the price.
What 80/20 or 78/22 nylon/spandex; polyester/spandex does not tell you
| Position | Value | Effect on swimwear fabric | Where it shows up |
|---|---|---|---|
| Floor | 80/20 or 78/22 nylon/spandex; polyester/spandex | Lowest cost, least margin for process variation | Spandex degradation in chlorine within a season |
| Working middle | 80/20 or 78/22 nylon/spandex; polyester/spandex | Predictable performance at a normal price | Nothing to negotiate, nothing to explain |
| Ceiling | 80/20 or 78/22 nylon/spandex; polyester/spandex | Best performance, highest cost | Cost the end product may not recover |
Buyers default to the floor because it is the cheapest compliant answer. That is rational until the first claim, and then the saving is measured against a replacement shipment.
The figure that decides the outcome is not composition itself but the tolerance around it. A supplier who quotes 80/20 or 78/22 nylon/spandex; polyester/spandex without a tolerance has not quoted a specification, and the first lot will define the tolerance for you.
How to measure composition
The reference method here is Chlorine resistance, run to ISO 105-E03 / retained elongation 50 h, with an acceptance of >= 80 % retained. The method is the easy part; sampling and conditioning are where reports diverge.
Take samples from the beginning, middle and end of the run. A single sample from the top of a roll tells you about the top of that roll, and composition varies more across a run than most buyers expect.
Record the measured value rather than pass or fail. A marginal pass on composition tells you the process is running at the edge, which is the information you need before the next lot rather than after it.
Composition does not stand alone
Composition moves with weight (180-260 gsm) and with stretch (4-way, 80-120 % elongation). Tightening one usually costs money in another, and a supplier who accepts every tolerance without comment has either not understood the interaction or is planning to substitute.
When you change composition, re-check the two neighbours before you approve the sample. Most of the samples we re-make are caused by a change in one figure that was not followed through.
The clause to write for composition
The line below is the version we can quote against without inventing anything. Composition appears with a tolerance and a test, not as a standalone number.
80/20 nylon/spandex, 220 gsm, 4-way stretch, recovery >= 90 % after 5 cycles, chlorine-resistant spandex, UPF 50+, colour fastness to chlorinated water >= grade 4, Pantone 19-2430 TCX
The clause that protects you is not the value, it is the sentence that says what happens when the value is missed. Put it in the purchase order, not only in the enquiry.
When composition goes wrong
Spandex degradation in chlorine. Swimsuits go limp and baggy after a season in a pool.
The cause is usually standard spandex breaks down in chlorinated water; resistance is a polymer choice, not a finish.
The test that catches it: ISO 105-E03 colour fastness plus retained elongation after 50 h chlorine immersion.
What to specify instead: Specify chlorine-resistant spandex for pool programmes, and say so in the care label.
None of this is visible in a quotation. It becomes visible in a retained sample and a lot record, which is why the paperwork matters more than the price on this parameter.
Four questions about composition, before you order
- What tolerance do you hold on composition, and what did your last three lots measure against it?
- Which method do you use for chlorine resistance, and which laboratory signs the report?
- When composition falls outside 80/20 or 78/22 nylon/spandex; polyester/spandex, do you rework, downgrade, or ship and hope?
- Which of weight or stretch would you move first to hit a lower price?
The answers are more useful than a certificate, because they show whether the process is controlled or merely inspected. Full ranges for swimwear fabric are on the product page, and the measurement regime is described on the quality control page.
Questions buyers ask before ordering
Do you stock chlorine-resistant spandex?
We buy it per order rather than stock it, because shelf life matters. Tell us the programme and we will specify the grade and the test evidence.
Can you match a print across a repeat order?
Yes if we keep the strike-off and the file. Always confirm the colour standard in writing, because screens drift.
Failure modes, and the test that catches each one
A specification only earns its keep if it names the failure it prevents. These are the two that matter for the swimwear fabric figures on this page.
| Failure | What triggers it | Test to demand on the production lot |
|---|---|---|
| Recovery loss at seams | Seam construction that does not stretch with the fabric. | UPF — AS/NZS 4399 or AATCC 183; acceptance UPF 50+ |
| Spandex degradation in chlorine | Standard spandex breaks down in chlorinated water; resistance is a polymer choice, not a finish. | Colour fastness to washing — ISO 105-C06; acceptance >= grade 4 |
The other two, with acceptance numbers attached, are in the full failure analysis for swimwear fabric. A supplier who cannot name the mode he sees most often is describing a catalogue, not a process.
From quotation to specification in seven lines
Leave the tolerance and the method out and every dispute is settled by whoever needs the goods more.
- Chlorine resistance: >= 80 % retained elongation after 50 h is the market band. Fix the figure you will test at goods-in, and the instrument you will test it with.
- UPF (UPF 50+): fix the value per shipment, and state who pays for the re-test if a lot lands outside it.
- Colour fastness to chlorinated water: >= grade 4 is not an answer on its own. Ask for the last three lots’ actual readings and the spread behind them.
- Lining: agree the test method with the number. Two labs, two methods, two answers, one argument.
- Sample retention: one production sample per lot stays with the mill for twelve months. Claims are settled against it, not against memory.
- Test reports: name the standard as well as the test. A pass on a development sample is not a pass on a production lot.
- Deviation rule: anything outside the agreed bands is reported before shipment, not after arrival.
Need composition specified and tested against your end use?
Send the end use, the quantity and the destination market, and we will come back with a specification that meets it, a price at your volume and the test reports that back it up. Samples are free for qualified programmes; we charge the courier only.
Related reading
- Swimwear Fabric vs Polyester/spandex
- Swimwear Fabric vs Knitted Fabric
- Swimwear fabric Specification
Sample cut with your values on it · Neutral packing and private label · Consolidation, documents and lead times
