What do people get wrong about washing swimwear?
This answer is a draft. It stays unpublished until legal review and source verification are complete.
"It stretched after one season" and "the colour faded" are complaints heard everywhere in the world, and most of the time the cause is how the swimsuit was washed and dried. In Japan the three enemies of swimwear are well known: pool chlorine, sea salt and sunscreen.
What to go on
| Step | What to do | Why |
|---|---|---|
| Straight after use | Rinse in fresh water (at the pool or beach if you can) | Removes chlorine, salt and sand. Do not leave it sitting wet |
| Washing | Press-wash in lukewarm water (30°C / 86°F or below) with a neutral detergent (the "delicates" type, おしゃれ着用). In a machine: laundry net + gentle cycle + short programme | Polyurethane is degraded by alkaline detergents, bleach and fabric softener |
| Removing water | Press between towels. Do not wring; keep the machine spin short | Fibres stretch |
| Drying | Reshape and dry in the shade. No direct sun, no tumble dryer | UV and heat fade the colour and weaken the stretch |
| Storage | Dry completely and store without sharp folds. Hangers stretch the shoulder straps, so lay it flat | — |
- Most swimwear is nylon or polyester plus 10–20% polyurethane, and polyurethane degrades with chlorine, UV, heat and time (a useful life of one to three years is the usual guide, depending on how often it is used).
- Sunscreen, especially oil-based sunscreen, causes yellowing and discolouration where it touches the fabric. Wait a while after applying before you put the swimsuit on, and keep it off the fabric when you reapply.
- Care labels in Japan use the international JIS L0001 symbols. Swimwear usually carries the tub-with-hand (hand wash), do-not-bleach, do-not-tumble-dry and dry-in-shade symbols.
[Verify] The polyurethane degradation and lifespan figures are general guides based on textile-industry bodies and makers' information.
Misunderstanding 1｜After the pool, just let it dry
Chlorine stays in the fibres after drying and keeps degrading them. Rinsing in fresh water the same day comes first.
Misunderstanding 2｜Get rid of the chlorine smell with bleach
Bleach damages polyurethane. Wash in a neutral detergent and rinse thoroughly; that reduces the smell.
Misunderstanding 3｜A tumble dryer is quicker and more hygienic
Heat destroys the stretch in polyurethane. Drying in the shade is quite enough; swimwear is thin and dries in a few hours.
Misunderstanding 4｜Hanging it on a hanger dries it faster
A wet swimsuit on a hanger stretches the straps and the fabric. Dry it flat, or lay it on a towel.
Misunderstanding 5｜Just carry the wet swimsuit home in a plastic bag
Sealed-in moisture starts mould and smell within a few hours. Rinse it, wrap it in a towel, and wash it as soon as you get home. If you use a plastic bag at all, keep it to the short trip home.
---
Sources
- Consumer Affairs Agency, "Care labelling (from 20 August 2024)" [洗濯表示（令和6年8月20日以降）]
https://www.caa.go.jp/policies/policy/representation/household_goods/guide/wash_02.html
- Japan Textile Products Quality and Technology Center (QTEC), "Degradation of polyurethane fibres" [ポリウレタン繊維の劣化]
https://www.qtec.or.jp/
- Japan Chemical Fibers Association, "Characteristics of synthetic fibres" [合成繊維の特徴]
https://www.jcfa.gr.jp/
⚠️ Editorial note: the source URLs above were identified by search. Our working environment cannot reach go.jp domains, so the contents have not been checked against the text. Verify every source before publication and record who checked it and when.
About this article
What we share here are ideas and everyday practices passed down among people living in Japan, together with general information drawn from public sources. They are not official recommendations, and they are not professional instruction. Practices vary between households and regions.
This is general information. Results vary from person to person and depend on your own conditions and surroundings.
Please decide for yourself, using your own judgement, whether any of this suits your situation. We cannot accept responsibility for any damage, loss or injury arising from following this article.
Follow the care label and the maker's instructions for any garment, shoe or bag. For expensive or sentimental items, ask a specialist cleaner or repairer.
Sources
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