Quality and testing

Fibre and yarn

HVI measures each cotton bale for length, uniformity, strength, micronaire, colour and trash. AFIS tests single fibres for what HVI misses: neps, short fibres, maturity and fineness, which predict yarn faults and uneven dyeing. Yarn tests:

USTER STATISTICS ranks results against world production: yarn at the 5% line beats about 95% of it, and the 50% line is the median. Buyers often specify a property at a level, such as CVm at the 25% line.

Fabric

Fabric is tested for the following, each result against a limit stated with its method:

• GSM and width; ±5% on GSM is a common tolerance.
• Dimensional change and spirality after washing.
• Pilling, graded against photographs from 5 (none) to 1 (severe).
• Abrasion resistance on the Martindale tester.
• Tensile strength (wovens) or bursting strength (knits).
• Colour fastness to washing, dry and wet rubbing, light and perspiration.
• pH of a water extract: OEKO-TEX STANDARD 100 allows 4.0–7.5 for skin contact.

Colour fastness is graded on grey scales, one for change in colour and one for staining of an adjacent white fabric, in half grades; light fastness is graded against blue wool references. Wet rubbing on dark shades is usually the hardest to pass.

• 5–1grey scale grades, from no change to severe
• 1–8blue wool scale for light fastness, from very low to very high

Garments and AQL sampling

Garments are measured at every POM against its tolerance and checked for fabric, sewing, print, label and packing faults. Final inspection checks a random sample under ISO 2859-1 (the US ANSI/ASQ Z1.4 uses the same tables). For a lot of 2,000:

1. Inspection levelGeneral level II, the usual choice, gives code letter K.
2. Sample sizeK means 125 garments, drawn at random from cartons across the lot.
3. Major defectsAt AQL 2.5: pass with up to 7, fail at 8.
4. Minor defectsAt AQL 4.0: pass with up to 10, fail at 11.
5. Critical defectsAnything unsafe, such as a needle fragment, fails the lot at one.

AQL is the worst process average the buyer will tolerate, not a promise for each lot. A major defect would likely bring the garment back (a hole, a measurement out of tolerance, a shade difference); a minor one departs from the standard without stopping sale or use.

Common test standards

Certificates and audits

Each certificate covers only its holder, sites, products and dates.