A swimsuit almost never fails at the fabric. The nylon face yarn will outlive your interest in the colour. What goes is the stretch — the suit comes out of a drawer in June loose at the leg line and slack across the back, the fit it had last year replaced by something softer and sadder. That is the elastane, and it was usually not worn out in the water. It was worn out in a sink or a washing machine.
Washing swimwear properly takes about five minutes and asks you to do less than you think, not more. Almost every instinct that makes sense for a cotton shirt — hot water, a decent dose of detergent, a hard wring, a hot dryer to finish — is specifically wrong here. It helps to know why, because the reasons make the routine obvious rather than fussy.
The fibre that actually fails
Elastane is a minority of a swim knit by weight and responsible for nearly all of its behaviour. It is a segmented polymer: rigid sections that hold the fibre together, linked by soft flexible ones that uncoil when you pull and pull themselves back when you let go. That recovery is a physical spring, and it depends on those soft segments staying as they were made. Heat loosens them. Hot water, a radiator, a tumble dryer or a sunny car roof lets the segments slip past one another into a new, longer arrangement, and the fabric sets there as it cools. Nothing tore. The spring was reheated and re-formed at the wrong length.
Why a washing machine is the wrong tool
A machine is an excellent device for applying mechanical energy to robust cloth, which is the opposite of what a swim knit needs. Even a cold delicate cycle tumbles the suit against the drum and against zips, hooks and denim in the same load, abrading a fine knit that gets its opacity from an unbroken surface. The spin is worse than the wash: it pins the garment to the drum wall under heavy force and holds it there stretched, wet and warm, for minutes. Wet fabric is at its weakest and most slippery, which is precisely when it least resists being deformed.
A suit is not damaged by being clean. It is damaged by the heat, the chemistry and the force we use to get it there.
Detergent: less, and nothing clever
Use a small amount of a mild, pH-neutral liquid — a capful in a basin, not a scoop. More detergent does not lift sunscreen faster; it mostly fails to rinse out and leaves a residue that stiffens the hand of the fabric. What matters more is what you keep away from it. Fabric softener is the quiet killer: it works by depositing a waxy film on fibres, which on swimwear clogs the knit, traps the body oils you were trying to remove and flattens the quick-dry behaviour you paid for. Chlorine bleach attacks the same links in elastane that pool water does, only at full strength. Optical brighteners build a dull cast on pale suits over a season, and enzyme-heavy biological powders are built for food stains on cotton.
The five-minute hand-wash
- 01Rinse the suit in cool fresh water straight after swimming, before any wash. That habit does most of the preservation work on its own.
- 02Fill a clean basin with cool to lukewarm water — comfortable on the inside of your wrist, never warmer.
- 03Stir a capful of mild liquid detergent through the water before the suit goes in, so it is never applied neat to the fabric.
- 04Submerge the suit, open out the lining and gusset, and squeeze the water through it gently for a minute. No scrubbing, no brushes.
- 05Soak for five minutes at most. A long soak does not clean a swim knit better; it only extends the exposure.
- 06Rinse in fresh cool water until no slip remains between your fingers. Residue left in the knit sits on the fibre until next time.
- 07Treat sunscreen marks on the spot with a drop of detergent and your fingertips, before they set.
Then stop washing and start drying, because the drying is half of it. Never wring or twist a suit: torsion concentrates the strain on a narrow band of fibres and is the most reliable way to leave a permanent ripple at a leg line or strap. Lay it flat in a clean towel, roll the towel once and press — that removes most of the water with no stretch at all. Dry flat in the shade on a rack or a dry towel, turned once. Do not hang a wet suit by its straps, because water is heavy and gravity will stretch the shoulders while the fabric is still relaxed, and keep it off radiators, out of dryers and out of direct sun.
Where RIVA stands
Every RIVA shape is cut from one double-lined sculpting Italian jersey woven at a family mill on Lake Como, chlorine and UV-resistant, chosen because it holds colour and shape across seasons, not one good summer. The seams are bonded rather than stitched, so there is no thread line to abrade in a wash. A better knit gives you more margin for error, not immunity from it, so our care advice stays four lines long: rinse in cool water after every swim, hand-wash gently, never wring, dry flat in the shade.