Alright. So you’re thinking about launching a swim line? Good. Bad idea. Great idea. Depends.
I’ve been knee-deep in this shit since 2010—first as a floor supervisor, then QC lead, now I run the show at Fexwear, our little operation out of Wuhan. We don’t do runway shows. We do production runs that actually ship on time and don’t fall apart after three washes.
You want to know about swimsuit fabrics? Not the glossy marketing version. The real one. The kind where someone yells in Mandarin because the dye bath ran hot again, or your sample comes back looking like it was made for a different planet.
Let’s talk.
Nylon Blends: The “Soft But Won’t Last” Dilemma
Nylon blends. Christ. Everyone loves them. Feels like butter. Looks expensive. Moves like water on skin. And if you’re selling bikinis on Instagram to women who post poolside selfies with coconut water in hand? Yeah, go with nylon.
But here’s what they won’t tell you: nylon ages like milk left in the sun.
I had a client last year—premium beachwear brand, launched via Shopify, influencer collabs, all very polished. They picked a 82% nylon / 18% spandex blend from a supplier in Guangzhou. Beautiful fabric. Soft hand feel. Rich colors. MOQ was low—just 300 units per style. Perfect for testing the market.
They sold out in two weeks.
Then came the returns.
Not many. Maybe 7%. But every single one said the same thing: “fabric pilled after one swim.” One. Swim.
We traced it back. Turns out the batch used recycled nylon—but not ECONYL®. Just some off-spec regrind fiber mixed in. It passed initial tensile tests (we caught this in a mid-line audit in 2023), but chlorine exposure accelerated surface degradation. Pilling started within 48 hours of first use.
So yeah. Nylon feels good. But durability?
Forget it.
And don’t even get me started on colorfastness.
Had another buyer insist on deep burgundy one-pieces. Used standard disperse dyes on nylon. Washed once? Turned the whole load pink. Pre-washing in vinegar didn’t help—because the mordant wasn’t set properly during dyeing. Factories skip steps when they’re running behind. Always.
Bottom line: If you’re going nylon, demand proof of dye lock treatment. Ask for AATCC Test Method 61 results. Don’t just nod when they say “it’s stable.” Get the damn report.
And for printing?
Don’t bother with sublimation on nylon unless you’re doing high-volume runs with specialty inks. At Fexwear, we had a batch last summer where the vector logos blurred into ghosts after washing. Cost us $8K in reprints. Now we flat-out warn clients: nylon is not printable at low volume. Full stop.
Use screen print if you must. Or switch fabrics.
Polyester Blends: Ugly Duckling That Wins the Race
Now let’s talk polyester.
Ugh. Sounds cheap, right? Like gym shorts from 2003.
But here’s the dirty secret no fashion blogger will admit: polyester blends are the backbone of competitive swimwear for a reason.
Take Speedo. Arena. TYR. They don’t use nylon. They use high-tenacity polyester blends. Why?
Because polyester doesn’t give a fuck about chlorine.
It doesn’t pill. It doesn’t stretch out. It doesn’t fade. And it holds prints like a goddamn vault.
I remember walking through a factory in Ningbo five years ago. They were producing suits for a European triathlon brand. 78% polyester / 22% elastane. Weight? 210 gsm. Tight weave. Textured surface.
The production manager handed me a sample that had gone through 50 simulated wash cycles with sodium hypochlorite solution.
Still looked new.
No fading. No loss of elasticity. Not a single pill.
That’s the stuff.
And here’s the kicker: polyester is digital print friendly.
Sublimation works perfectly on it. Colors pop. Lines stay sharp. Even after repeated exposure to saltwater and UV, the print integrity holds.
We did a run for a Miami-based brand—custom tropical prints, palm trees, flamingos, all over one-pieces. Used sublimated 80/20 poly-spandex. Printed in Dongguan. Shipped to Florida. Customer feedback? “Looks better after six months than it did day one.”
And cost?
Cheaper than nylon.
Not by much. But when you’re scaling, even $0.30 per unit matters.
Only downside?
Feel.
Yeah, older polyesters felt like sandpaper. But modern ones? Blended with micro-denier fibers, brushed finishes, mechanical stretch—we’re talking next-to-skin soft now.
I keep a swatch book in my office. Show it to founders who scrunch their nose at “polyester.” Most can’t tell the difference between it and nylon by touch alone.
So stop hating on polyester.
It’s the workhorse that actually survives the war.
What Else to Look For (When You’re Not Just Guessing)
Alright. So you’ve picked your base fiber. Now what?
Let’s go deeper.
Weight: Don’t Let Your Suit Turn Into a See-Through Nightmare
Fabric weight isn’t just about drape. It’s about function. And dignity.
Most fashion swimwear sits between 180–200 g/m². Light enough to move. Heavy enough to hold shape.
But listen—if you’re designing white or pastel pieces, do not go below 250 gsm.
I learned this the hard way.
Client wanted minimalist cutouts. White fabric. Went with 210 gsm poly blend. Seemed fine in studio photos.
Then customers started posting videos.
Guess what happens when sunlight hits thin white swim fabric?
You become a walking X-ray.
Returns flooded in. “Sheer,” “embarrassing,” “needed to wear underwear.”
We lost 14% of that batch.
Since then? Rule is simple: light colors = heavier fabric. Period.
If you want that lingerie-like feel (and some do—there’s a market for sheer mesh overlays), use dual-layer construction. Never rely on single-ply under 230 gsm for coverage.
And test it. Hang a swatch against a window. Take a photo. Send it to your team. Ask: “Would you wear this to the beach?”
If anyone hesitates, scrap it.
Composition: Spandex Isn’t Magic—It’s Chemistry
Everyone throws around “spandex” like it’s a cure-all.
“More spandex = more stretch = better fit.”
Bullshit.
Spandex (or elastane, or LYCRA®—same family) gives you recovery. Stretch without sag. But too much and your suit feels rubbery. Like wearing a tire inner tube.
Ideal range?
15–22% elastane.
Below 15%? Fabric won’t hug curves. Loses compression. Athletes hate it.
Above 22%? Becomes stiff. Hard to sew. Stretches unevenly during cutting. Waste goes up. Cost goes up.
And not all spandex is equal.
LYCRA® Xtra Life™? That’s the gold standard. Resists chlorine degradation. Holds shape for 300+ hours in chlorinated water.
Generic Chinese elastane? Might last 50 hours before losing 30% of its elasticity.
We tested this ourselves—ran identical suits side-by-side in a public pool for eight weeks. One with LYCRA®, one with generic. After week six, the generic started bagging at the hips. LYCRA® suit? Still tight.
Difference in cost per yard? $0.40.
Worth every cent.
Also—check how the spandex is integrated.
Is it core-spun? Wrapped? Knitted in?
Core-spun lasts longer. Wrapping prevents direct chlorine contact.
These details matter.
Ask for fiber specs. Not just percentages. The actual yarn type.
If they can’t provide it, walk away.
Quick-Drying: Because Nobody Likes Sitting in a Wet Suit
This should be obvious.
But I still see brands using fabrics that absorb water like a sponge.
Swim fabric should wick. Fast.
Polyester? Naturally hydrophobic. Wicks moisture instantly.
Nylon? Absorbs slightly more—but still okay if engineered right.
Key is the knit structure.
Tight gauge knits with capillary channels move water outward. Then evaporation kicks in.
We had a prototype once—mesh-backed bikini top. Looked sexy. Breathable. But dried slower than denim.
Why? Open mesh trapped water droplets. Took 45 minutes to dry in sun.
Switched to a rib-knit with directional wicking. Dried in 12 minutes.
Big difference when you’re hopping from ocean to bar.
Test drying time yourself.
Put a swatch in water. Pull it out. Time how long until surface moisture disappears.
Under 15 minutes? Good.
Over 30? Reconsider.
Sustainability: Not a Buzzword—It’s a Liability Avoidance Tool
Sustainability.
Ugh. I know. Feels like PR fluff.
But here’s the truth: if you’re sourcing synthetics and ignoring ECONYL®, you’re risking your brand’s future.
ECONYL® isn’t just “recycled nylon.” It’s regenerated nylon.
Made from old fishing nets, carpet fluff, industrial waste. Cleaned. Melted. Repolymerized.
End product? Indistinguishable from virgin nylon.
But impact?
Massive.
One ton of ECONYL® saves 7 barrels of crude oil and cuts 5.7 tons of CO₂ equivalent.
And consumers notice.
We ran an A/B test for a UK brand—one line with virgin nylon, one with certified ECONYL®. Same design. Same price.
ECONYL® line outsold the other by 3.2x in six weeks.
People pay more. They demand it.
But—and this is critical—you must verify certification.
Too many suppliers claim “eco-friendly” without proof.
At Fexwear, we only source ECONYL® with full traceability docs. Batch numbers. Certificates from Aquafil, the manufacturer.
No paperwork? No fabric.
And yes, it costs more. 10–15% premium.
But so does a PR disaster when Greenpeace calls you out for greenwashing.
Stretch & Recovery: The Real Test Is in the Sewing Room
Stretch isn’t just about comfort.
It’s about manufacturability.
I’ve seen factories reject entire rolls of fabric because the crosswise stretch exceeded 40%.
Why?
Because automated cutters can’t handle it. Fabric shifts during laying. Pieces come out misaligned. Waste skyrockets.
Rule of thumb: keep total stretch under 35% in any direction unless you’re using manual cutting.
And recovery?
Even more important.
A suit can stretch on. But if it doesn’t snap back?
It’s garbage.
Test recovery like this:
- Stretch a 10cm swatch to 15cm.
- Hold for 30 seconds.
- Release.
- Wait 60 seconds.
- Measure again.
If it’s not back to ≤10.5cm? Fail.
We had a batch fail this test once. Elastane degraded during heat setting. Suits stretched out after first wear. Client had to eat 10% returns last year. Brand trust tanked.
So test early. Test often.
Comfort: Chafing Is a Dealbreaker
You can have the best fabric in the world.
But if it chafes?
Nobody buys a second one.
Comfort isn’t just softness.
It’s seam placement. Flatlock stitching. Gutter seams. Lining quality.
I walked into a QC room once and saw a woman rubbing her inner thigh. She’d been testing prototypes all morning.
“This one’s shredding my skin,” she said.
Turns out the side seam was raised. Micro-stitching issue. Barely visible. But brutal after 20 minutes.
We scrapped the entire pre-production run.
Lesson?
Always do wear trials.
Get real bodies. Different sizes. Move in water. Dry off. Sit down.
Watch where friction happens.
Adjust pattern accordingly.
And never, ever skimp on lining.
Unlined thin fabric on sensitive areas? Recipe for pain.
Figure-Flattering: Compression Isn’t Just Marketing
“Slimming effect.” “Tummy control.” “Lift and shape.”
All bullshit… unless backed by engineering.
Real figure-flattery comes from graded compression zones.
Think: higher denier yarns in core areas. Strategic paneling. Seamless knitting.
We worked with a brand targeting postpartum women. Needed gentle abdominal support without constriction.
Solution? 4-zone gradient compression knit.
Hip panels: 18% stretch.
Waist: 12% stretch (higher denier).
Bust: molded cups with encapsulation.
Result? 94% positive feedback in customer surveys.
Not magic. Science.
And yes—it cost more. But they charged a premium. Sold out twice.
So if you’re promising “figure-flattering,” deliver it structurally.
Not with Photoshop.
Anti-Pilling: Because Nobody Wants a Fuzzy Bathing Suit
Pilling.
Tiny balls of fiber. Looks like mold. Feels awful.
Nylon? Pilles fast. Especially when exposed to chlorine.
Polyester? Resists it.
But not all polyester.
Low-twist yarns? High risk.
Loose knits? Worse.
We had a supplier once who blended in short-staple recycled PET. Seemed fine. Passed lab tests.
Then after 10 wears? Pills everywhere.
Sent it to SGS for analysis.
Turns out the fiber length was inconsistent. Short fibers migrated to surface. Rubbed together. Formed pills.
Now we specify minimum filament length: 45mm for recycled poly.
And we do Martindale abrasion tests—minimum 30,000 cycles before surface change.
If it fails, we don’t buy.
Simple.
Ease of Care: Washer-Safe or Bust
Here’s a fact: most people don’t hand-wash swimsuits.
They toss them in with jeans. Hot water. Harsh detergent.
If your fabric can’t survive that?
You’re setting yourself up for failure.
Best practice?
Design for abuse.
Use fabrics that tolerate machine washing. Low shrinkage. High colorfastness.
We recommend:
- Max 30°C wash
- No bleach
- Hang dry
But also—make sure it survives accidental misuse.
We tested one fabric at 40°C with regular detergent. Shrank 8%. Color faded 2 shades.
Never shipped it.
Another? Withstood 50 hot washes. Still intact.
That’s the one we use.
And label care instructions clearly.
Not “hand wash only” and hope they comply.
Be realistic.
Case Study: The $120K Mistake (And How We Fixed It)
Startup founder. Smart guy. Ex-tech. First fashion venture.
Launched a luxury swim line. All nylon-blend. Italian fabric. Gorgeous prints. MOQ 500 units.
Sold out in days.
Then the emails came.
“Suits stretched out.” “Colors bled in wash.” “One-piece turned sheer in sunlight.”
We got called in.
Inspected remaining stock.
Findings?
- Fabric was 75/25 nylon/spandex—but elastane was non-chlorine-resistant.
- Dye process skipped fixation step.
- Weight was 210 gsm—fine for dark colors, but white pieces were semi-transparent.
Total loss? $120K.
We helped him pivot.
Switched to 78/22 ECONYL® with LYCRA® Xtra Life™. Weight bumped to 260 gsm for light colors. Added mesh lining for coverage.
Redesigned prints for sublimation on polyester base.
New MOQ: 300 units.
Cost per unit went up 18%.
But sell-through rate? Higher than first run.
And zero returns for quality issues in first quarter.
Lesson?
Don’t fall for “premium” fabric names.
Test. Verify. Demand data.
Case Study: The Fitness Brand That Didn’t Know Its Own Customers
Mid-sized activewear brand. Did leggings, sports bras. Decided to expand into swim.
Assumed their audience wanted the same thing: compression, sweat-wicking, bold prints.
So they launched a swim line with heavy-duty poly blend. 240 gsm. Thick. Durable.
Fit? Snug. Almost restrictive.
Sales? Crashed.
Why?
Swim customers aren’t the same as gym customers.
Gym-goers want support.
Beach-goers want freedom.
Lightness. Softness. Easy on/off.
Their suits felt like armor.
We suggested a dual-line approach:
- Performance swim (for triathletes, lap swimmers): high-compression, durable, quick-dry.
- Lifestyle swim (for resort, beach): lighter fabric (190 gsm), softer hand, relaxed fit.
Split production.
Performance line kept existing branding.
Lifestyle line got a sub-brand, softer visuals.
Result?
Lifestyle line outsold performance 3:1.
Sometimes the market tells you who you are.
Listen.
Fexwear: Not a Sales Pitch—Just How We Survive
Look, I’m not here to sell you on Fexwear.
But I will say this: we’ve survived 14 years because we don’t cut corners.
We’ve got our own factory in Wuhan. Started in 2010. Low MOQs. Fast samples. Private label. Full logistics.
We’ve burned batches. Lost clients. Had midnight calls about dye lots.
But we’re still here.
Because we test everything.
From fabric sourcing (like this guide we put together after one too many client disasters), to production oversight, to shipping.
We’ve helped over 5,000 small brands—not just with design, but with damage control.
Need help picking fabric? Talk to us . No pressure.
Want to see what we make? Check the catalog .
Or just visit the main site and poke around.
But don’t expect slick promises.
Expect reality.
Alright, I’ve got to get back to chasing a dye-lot issue. That’s enough for now.
FAQs
Q: Can I mix nylon and polyester in one suit?
Yeah, but it’s risky. Different dye uptake rates. Heat sensitivity varies. We saw this exact failure in 2 factories last year—panels shrank at different rates. Stick to one base fiber unless you’ve got a killer tech pack.
Q: Is ECONYL® worth the extra cost?
For premium brands? Absolutely. We had a client recoup the margin difference in pricing power alone. Plus, fewer returns. Better reviews.
Q: What’s the lowest MOQ you’ll do?
Depends. 100 units if it’s simple. More complex? 300. We’re flexible. Startups need breathing room.
Q: Do you handle certifications?
Yes. BSCI, WRAP, OEKO-TEX, ISO—all covered. We audit our own lines. Third-party checks too. Paperwork’s boring, but necessary.
Q: How fast can you turn a sample?
7 days rush. Normal is 12–14. We’ve done 5-day miracles—but only when the moon aligns and nobody takes a sick day.
Q: What if the fabric I want isn’t on your list?
Send us a swatch. We’ll test it. Source it. Or tell you why it’s a bad idea. No ego here.
You’ve spent time reading this. Now I want to hear from you.
What’s the worst fabric fail you’ve seen?
Ever ordered a roll that looked nothing like the swatch?
How do you test for quality when you can’t visit the factory?
Drop a comment. Share your war story.
We’re all figuring this out together.