A composition label is one of the few places a swimwear brand is obliged to tell you the truth. Everything else on a product page was written by a copywriter; the little tag inside the side seam was written by a regulation. The difficulty is that it speaks a language nobody teaches you — a fibre name, two percentages, and a fabric word that sounds like a description but is really a form of construction.
It is worth knowing what the label cannot tell you, too. Composition describes what a fabric is made of, never how well it was made. Yarn quality, knit density, dye process and finishing all vary enormously inside an identical set of percentages, and two suits reading the same numbers can behave like entirely different garments. The label narrows the field. It does not settle the question.
Nylon, polyamide, polyester: the fibre doing the covering
This is the majority fibre, usually somewhere near four-fifths of the fabric, and it sets the hand, the depth of colour and the way the suit ages. Nylon appears on European labels as polyamide; the two words are the same fibre, and seeing one rather than the other tells you nothing except where the tag was printed. It is soft, takes dye to a rich saturated shade and recovers well from stretch, which is why most premium swimwear is built on it. Polyester is tougher against chlorine and sunlight and dries marginally faster, which is why it dominates lap-pool and team swimwear, but it is firmer against the skin and harder to dye to a deep, even colour. Neither is simply better. They are trade-offs between softness and stamina.
Elastane, spandex and Lycra: three names for one job
Elastane is the stretch fibre, and it is where most of the confusion begins. Spandex is the North American name for the identical fibre, and Lycra is a brand name for one manufacturer's version of it. Seeing all three words is not evidence of three materials. Elastane rarely exceeds a fifth of a swim fabric, and that small share is responsible for two quite different properties: stretch, which almost any elastic fibre delivers, and recovery, the snap back to shape afterwards, which decides whether the suit still fits in August. Chlorine, heat and sunscreen oils attack elastane specifically. That is why a swimsuit almost always fails by going slack rather than by wearing through.
A composition label tells you what a fabric is made of. It cannot tell you how well it was made — that is a question only water answers.
Jersey, tricot, knit: how yarn becomes fabric
Jersey is not a fibre at all. It is a structure — loops of yarn rather than threads crossed over one another — and knitting is the reason swim fabric moves in four directions when a woven cloth of the same fibres would barely move. Most swim fabric is warp-knitted, which you may see called tricot, a construction that is dense, smooth and far less inclined to run when it catches on a rough tile. Weight is the other half of the story, usually quoted in grams per square metre. A heavier knit generally means more opacity and more substance under tension; a very light one packs small and vanishes when wet.
The words that are claims rather than composition
Everything printed after the percentages is marketing language, which does not make it worthless — it means only that nobody official is checking it. Some of those words are precise and genuinely useful once you know what they are claiming, and some are decoration. This is the short version worth carrying into a product page.
- 01Polyamide — the European label word for nylon. Same fibre, different name.
- 02Elastane, spandex, Lycra — the stretch fibre. The last is a brand of the first two.
- 03Recovery — how completely the fabric returns to shape after stretching. The quality that decides how long a suit fits.
- 04Compression — fabric with enough tension to smooth and hold rather than merely cover. It should feel snug when new.
- 05Double-lined — a full second layer of knit front and back, as opposed to a small hygiene liner.
- 06Regenerated or recycled nylon — new fibre spun from nylon waste rather than from virgin material.
- 07GSM — grams per square metre, the fabric's weight, and a rough proxy for opacity and substance.
- 08Chlorine-resistant — a claim about how the fibre survives pool water. Meaningful, and never a licence to skip the rinse.
Where RIVA stands
RIVA's own label is short by design. The whole collection is built on one sculpting Italian jersey from a family mill on Lake Como, chosen for compression and recovery rather than for novelty, and every shape is fully double-lined in that same fabric so that opacity never depends on how hard the suit happens to be stretched. The shells are spun from regenerated ocean nylon, the fibre is chlorine and UV-resistant so colour and shape survive more than one season, and the seams are bonded. None of that exempts a suit from care: rinse in cool water after every swim, hand-wash gently, never wring, and dry flat in the shade. Read our label the way you would read anyone else's, then judge the suit wet — the only place a fabric cannot hide.