Aug 12, 2026

How Does UV Exposure Affect Swimsuit Materials?

You buy a cute swimsuit in May. By August, it is saggy, faded, and the elastic is shot. The sun did that. Not just chlorine or saltwater. UV rays break down the fibers holding your swimsuit together. Many people do not understand the aggressiveness of the sun's rays on fabric. It is not only about sunburns; the same rays burn through your swimsuit from inside. UV-resistant swimsuit fabrics matter and are taken into account by Beachbum while designing gear for swimming.

Let us see what the scientific studies say about the destruction of swimwear by sunlight and how to protect yourself from it.

What Is Ultraviolet (UV) Degradation?

UV light carries energy. When it hits synthetic fibres, that energy breaks the chemical bonds holding the material together. Textile scientists call this Ultraviolet (UV) degradation — a slow, constant process. Research on nylon webbings shows the damage clearly. UV weakens tensile strength, fades colour and causes surface cracking. The stretchy elastane in swimwear is more vulnerable — light, heat and pollutants attack it.

The warning signs in your own suit:
Faded colour, especially on dark suits.
A baggy fit where elastane used to hold.
Fabric that goes thin or see-through when wet.
Brittle fibres that crack along the seams.

What Does UPF (Ultraviolet Protection Factor) Tell You?

UPF (Ultraviolet Protection Factor) works like SPF, but for cloth. A UPF 50 fabric lets only 1/50th of UV through, about 2%. In plain terms, that blocks roughly 98% of rays. The numbers in context:

According to MD Anderson Cancer Center, most standard swimsuits sit around UPF 5.
About 20% of UV still reaches your skin in those.
The Skin Cancer Foundation warns wet or stretched fabric loses protection.
Dark colours and tight weaves block more UV.

Here's the catch. UPF is measured on new, dry fabric. The suit you actually wear gets wet, stretched, and sun-soaked. So treat ratings as a starting point, not a guarantee.

Which Swimsuit Fabric Holds Up Best in the Sun?

Polyester is the clear winner for UV. It naturally blocks more rays than nylon, starting around UPF 15. Nylon — also called polyamide — feels softer but degrades faster under sunlight and absorbs more water. Elastane gives swimwear its stretch, but it's the first fibre to break down. Lab testing shows strength drops sharply after about 300 hours of chlorine and sunlight — 35 days of summer wear. The fabric rundown:

Polyester: best UV resistance and shape retention.
Nylon or polyamide: soft and quick-drying, but more UV-sensitive.
Elastane or spandex: essential for stretch, first to give out.
Non-resistant fabric can lose over 60% of its strength in chlorinated water.
Stretched fabric lets more UV through.

Don't let your swimsuit get damaged by harsh sunlight

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How Do You Slow UV Damage? (Care Tips That Work)

You can't stop UV. You can slow it down. Rinse your suit in cold water after every swim — salt and chlorine speed up fibre breakdown, so make it a habit.

Dry suits in the shade. Radiators cook the fibres.
Never wring or tumble dry. Twisting snaps stretch fibres.
Rotate between two suits so each gets a rest day.
Replace a suit that goes see-through or loses its snap.

What Makes UV-Resistant Swimsuit Fabrics Different?

UV-resistant swimsuits have been made for specific purposes. The fabrics contain dense weave construction that absorbs ultraviolet light instead of allowing it to pass through. Some manufacturers also incorporate UV absorbers during production.

Tight weaves physically block more rays.
Darker dyes absorb UV instead of passing it.
Denser fibres leave less room for rays to sneak through.

UV Swimwear We Stand Behind: The Beachbum Take

We're a UK brand designed in Dorset by people who paddle, surf and swim for a living. When we built our swim range, sun resistance was a requirement, not an afterthought. Our one-pieces use buttery-soft recycled polyamide with UPF 50+ protection. They dry fast, stay put, and feel good from sunrise swims to sunset paddles. This is Beachbum swimwear, built for real days out. Why our swim range earns its keep:

UPF 50+ fabric blocks about 98% of UV rays.
Recycled polyamide — soft, quick-drying, planet-friendlier.
Designed in Dorset by watersports pros.
Long-sleeve £60, sleeveless £45, secure stay-put fit.
Rated 4.9/5 from over 3,800 reviews.
Featured in Harrods, Vogue, BBC, National Geographic, The Times.

Ready to retire your faded, stretched swimsuit?

Browse the Beachbum Collection

Conclusion

UV is the quiet killer of swimwear. It fades colour, loosens stretch and thins fabric while you're busy making memories. You can't see it happening, but you can prepare for it. Choose gear with real UPF ratings and look after it properly. When the old suit finally gives up, check out our Beachbum swimwear range. It's built for the water, not just the photos.

FAQs

Does Beachbum make its swimsuits with UV-resistant swimsuit materials?

Yes. We design our one-pieces using recycled polyamide that has the UPF 50+ rating. It prevents 98% of UV rays from passing through. It makes these materials UV-resistant swimsuit materials.

How does UV affect swimsuit materials?

The ultraviolet energy damages the chemical bonds of synthetic fibers, such as nylon, polyester, and elastane. It results in fading, brittleness, and deterioration of the material. The elastane fibers suffer the most, causing swimsuits to lose their tightness.

What UPF rating does swimwear need to have?

UPF 50 and above will do best. With UPF 50, less than 2% of UV passes through. So, UPF 50 blocks more than 98%. Regular swimsuits have about a 5 UPF rating, which means that 20% of UV can pass through.

Does wet swimwear offer less sun protection?

Yes. The Skin Cancer Foundation says wet or stretched fabric loses some protective ability and becomes more transparent. Since the fabric becomes closer when the suit is wet, this leads to a greater opening of the fibers, and therefore more UV can penetrate.

How long will your swimsuit last with constant exposure to the sun?

It depends on the material used and your care for it. Research has shown that after about 300 hours of exposure to chlorine and sunlight, there is a great reduction in strength. So, that’s about 35 summer days. Cheaper swimsuits won't survive even one season.