Swimwear fabric Specification: What Each Number Actually Changes

Two suppliers can quote the same swimwear fabric at the same headline figure and deliver different products. The difference is in the numbers nobody puts in the quotation, and in the tolerance behind the number that is quoted.

Why the headline number is the least useful one

Every quotation leads with composition. It is easy to compare and it is the number the factory can hit most cheaply. But it tells you almost nothing on its own: composition sets the frame, and the parameters below set whether the product survives its first year in service. A buyer who compares only the headline figure is buying a sample, not a supply agreement.

For swimwear fabric, the practical rule is to fix the headline figure at the level your product needs and then spend your negotiating attention on stretch and stretch recovery. Those two are where cheap goods differ from adequate goods, and they are usually absent from the quotation sheet.

The numbers that decide performance

Read the table as a set of trade-offs rather than a checklist. Moving any single line usually costs money somewhere else, and the cheapest way to hit one figure is often to let another slip.

Composition

Typical range: 80/20 or 78/22 nylon/spandex; polyester/spandex. Nylon feels better and dyes deeper; polyester survives chlorine and price pressure better.

Weight

Typical range: 180-260 gsm. Coverage and opacity. Under 190 gsm, light colours need a lining.

Stretch

Typical range: 4-way, 80-120 % elongation. Two-way stretch is cheaper and wrong for a one-piece.

Stretch recovery

Typical range: >= 90 % after 5 cycles. Bagging at knees and seat is a recovery failure, not a fit failure.

Chlorine resistance

Typical range: >= 80 % retained elongation after 50 h. The specification that separates pool swimwear from resort wear.

How to write a swimwear fabric specification that protects you

A specification is only useful if a substitution becomes visible. That means writing the construction and the performance together, and naming the test that proves each one. For swimwear fabric, the clause has to pin stretch and stretch recovery, because those two separate a compliant lot from an adequate one:

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

Note what is missing from that line: adjectives. No ‘high quality’, no ‘premium’, no ‘export grade’. Every clause is either a number with a tolerance or a named test. If a supplier cannot quote against a line written this way, that is information about the supplier.

Where the specification usually breaks down

The first failure is 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 exposes it before you order: ISO 105-E03 colour fastness plus retained elongation after 50 h chlorine immersion.

The second is colour bleeding. Dark and bright shades bleed into linings and onto towels. It comes from poor wash-off after dyeing, or a shade that exceeds the dye class capability. Test with ISO 105-E03 and ISO 105-C06 multi-fibre staining. and write the result into the purchase order, not just the enquiry.

Both failures share a pattern: they appear months after delivery, they are hard to attribute, and the cost lands on the buyer rather than the mill. That is exactly why the test belongs in the specification and the report belongs in the shipment file.

What to put in a swimwear fabric enquiry

1. End use and the conditions, which together decide where stretch has to sit inside 4-way, 80-120 % elongation.
2. The one figure that must hold, with chlorine resistance named as the proof.
3. Quantity per colour and per delivery, against a typical MOQ of 300-500 kg per colour or print.
4. Destination market, because compliance changes the construction, not just the paperwork.
5. A physical standard viewed under a stated light source, not a screen proof.

With those five points we can quote against a real requirement instead of a generic range. Full ranges sit on the swimwear fabric page, and the manufacturing side of the same question is on our 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.

What is the MOQ for digital print?

Typically 300-500 m per design; below that setup dominates the price.

Failure modes worth a clause in the purchase order

Claims rarely come from a batch that was obviously wrong. They come from a stretch figure that sat inside the quoted band and outside what the product needed.

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.

Seven lines that turn a quotation into a specification

Most post-delivery arguments are not about quality. They are about a document that never said which figure would be measured, on which instrument, at whose cost.

1. Stretch recovery: agree the test method with the number. Two labs, two methods, two answers, one argument.
2. Chlorine resistance (>= 80 % retained elongation after 50 h): state where in the band this order sits. The middle of the band is not what a tolerance is for.
3. UPF: the figure you will accept inside the UPF 50+ band, the tolerance on it, and the method used to measure it.
4. Colour fastness to chlorinated water (>= grade 4): name the number, not the word. If the answer only repeats the band, ask which point inside it is being offered for this order.
5. Price validity: the period during which the quoted figure holds, and what happens to it when the raw-material index moves.
6. Remedy: rework, replacement or credit, and the point at which each applies.
7. Sample retention: one production sample per lot stays with the mill for twelve months. Claims are settled against it, not against memory.

Related reading

• Stretch recovery in Swimwear fabric
• What Swimwear Fabric Really Costs
• Swimwear Fabric vs Knitted Fabric