Three Things Will Destroy a Swimsuit: Wrong Dye, Wrong Elastic, No Lining
Swimwear is the smallest garment in fashion by fabric weight, and technically one of the most demanding to make correctly. Three specific things will destroy it — and all three come down to a single environmental fact: pool water contains chlorine.
This is not a quality aspiration. It's a minimum functional requirement.
Why chlorine changes everything
Pool water holds chlorine at 1–3 parts per million — a small concentration, but sufficient to bleach most standard reactive dyes within weeks of regular use, degrade standard polyester or nylon elastic to failure within a single season, and delaminate any adhesive-bonded lining or cup construction.
The three non-negotiables
Chlorine-resistant dye
ISO 105-E03, Grade 4 minimum
Standard reactive dye bleaches visibly within weeks of pool exposure.
Test: 10 hours pool exposure at 1–3 ppm before bulk approval.
Chlorine-resistant elastic
85%+ tension after 20 pool sessions
Standard elastic loses 30–50% tension in a single season, causing sagging and gapping.
Specify by name — Fulflex, Filatice, or equivalent — on the tech pack.
Full lining throughout
no unlined panels, ever
Every panel double-layered, for hygiene, opacity, and structure.
Unlined swimwear intended for pool use is a sample, not a commercial product.
Worth knowing
Any failure on any of these three tests means: do not proceed to bulk. There's no partial credit — a suit that passes dye and lining but fails elastic tension will still fail in the field.
The takeaway
Every other swimwear spec — style, cup, print, hardware — is a design decision. These three are physics. Get them wrong and the garment fails visibly, regardless of how well everything else was executed.
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