The sample passed. The bulk went see-through.

This is the most expensive legging failure there is, because it reaches the customer before it reaches QC. The search is “squat proof leggings manufacturer”. The real question is why an approved sample did not predict the bulk.

What the buyer brought

An approved sample that was opaque, a bulk delivery that was not, and customer photos taken under phone flash — the harshest test a legging meets. The previous factory pointed at the mill. The mill pointed at the colour. Nobody had written down what “opaque” meant, at what stretch, in which shade.

How we tell the causes apart

Before anyone changes fabric, the approved sample and a failed bulk piece go side by side. Four quick checks usually name the culprit:

• Weight. Equal-area panels cut and weighed from both. A lighter bulk panel points to finished weight or width.
• Density. Courses and wales counted per centimetre under a pick glass. Fewer loops means a more open knit, even at similar weight.
• Stretch. Both pulled to the same load. If bulk stretches further, the seat opens further at the same squat.
• Pattern. Only light colours failing points to shade; only large sizes failing points to stretch and grading; everything failing points to the fabric itself.

Root cause — usually several at once

• Sample yardage is not the bulk lot. Bulk was knitted and dyed separately, sometimes on a different machine or with a substituted yarn.
• Heat-set too wide. Setting the fabric wider gains metres per kilo for the mill and costs opacity for the brand. Nobody had specified finished width.
• The lightest shade is the weakest. Stone, sage and heather grey hide less than black on the same knit. Approval happened on the darkest colour.
• The largest size stretches the most. Opacity at the base size says little about the seat of the largest size at full squat.
• No written defect definition. “Sheer” was not on the inspection sheet, so it could not fail a lot.

The gates we install

1. Name the base. PowerForm™ 215 for the light neutrals. The fabric decision is written, not implied by “same as before”.
2. A fabric PO the mill signs. Composition, finished weight, finished width and stretch, each with a tolerance agreed before knitting — so a light or over-wide lot is a mill rejection, not a garment surprise.
3. Incoming check per lot. Weight and width measured on relaxed fabric before it is released to cutting.
4. Opacity check on the bulk lot. Lightest colour, stretched to the elongation the largest size’s seat sees in a deep squat, over a black-and-white contrast card, photographed under flash and daylight. Done before cutting.
5. PPS cut from bulk fabric, in the lightest colour, squat-tested on a body in the largest size.
6. Inline 20/50/80% with a fresh opacity check whenever a new dye lot enters the line, and a retained swatch of the approved lot kept as the reference for every reorder.
7. Sheerness written as a defect in the final inspection under the buyer’s AQL protocol, so it can fail a lot rather than start an argument.

What to send us first

• The approved sample and at least one failed bulk piece — ideally in the lightest colour and largest size that failed.
• Lot or dye-lot numbers from the cartons or labels, so we can see whether one lot or every lot failed.
• Customer photos or return reasons by colour and size.
• The fabric spec the previous supplier quoted, if you have it.

The result we will sign

No bulk cut until the bulk-lot opacity check and the PPS pass. Fabric that fails is not cut; a replacement lot resets the calendar, and we give the new date in writing rather than shipping on time and sheer. Sample US$50–100 per garment piece in 7–9 working days. MOQ 150 per style per colour.

What we will not promise

A blanket “100% squat proof” label for every shade and size, or a percentage drop in returns. Opacity depends on colour, size and stretch, which is why the gate is written per programme.

Related: squat-proof fabric testing · GSM for leggings · PowerForm™ · PPS approval checklist · leggings manufacturer.

Other rescues: Factory switch without the pattern · One colour across three fabrics · Pilling and colour transfer · First wholesale account · all reconstructions.

Send the failed sample and the approved one

FAQ

Why did the sample pass if the bulk failed?

The sample was cut from sample yardage. Bulk was knitted, dyed and heat-set as a separate lot — often set wider for yield, which lowers the finished weight and opens the knit. Opacity was never checked on the cloth that shipped.

Is a higher GSM the fix?

Not by itself. Opacity depends on knit density, yarn, spandex content, finished width and shade as much as on weight. A heavier fabric set too wide can still show through. We write GSM, finished width and stretch on the fabric PO, then test opacity at the stretch the largest size actually sees.

Do you guarantee leggings will never be sheer?

No factory can promise that for every shade and size. We promise the gate: the bulk lot is opacity-checked on the lightest colour at the largest size before cutting, and fabric that fails is not cut.

Does a rescue order have a lower MOQ?

No. Standard MOQ stays 150 pcs per style per colour. A selected library trial from 100 applies only when the block and the fabric both qualify.