Textile Testing and Quality Control
What the exam tests
Testing covers sampling, the standard instrument for each property and the calculation of a quality index. Expect items on count, strength, evenness and colour fastness, plus one numerical question.
Fibre and yarn tests
- Cotton fibre: staple length (Baer sorter, HVI); micronaire 3.5–4.9 µg/inch (fineness combined with maturity, below 3.0 is immature); fibre strength on Stelometer or HVI.
- Yarn count: Ne is the number of 840-yard hanks per pound; tex is mass in grams per 1000 m. They are inversely related, Ne × tex ≈ 590.5.
- Lea strength: a 120-yard skein broken on a pendulum tester. Count strength product CSP = lea strength in pounds × yarn count in Ne.
- Evenness: the Uster evenness tester gives CV% and IPI (thin places, thick places, neps); hairiness is reported as the Uster H value.
Fabric tests
GSM by cutter, ends and picks per inch by counting glass, tensile by strip or grab method, tear by Elmendorf, bursting by diaphragm, abrasion and pilling by Martindale, colour fastness to washing, rubbing, light and perspiration. Defects are graded by the 4-point system and judged against an AQL, commonly 4.0.
Worked example
A 40s yarn gives a lea strength of 90 lb. CSP = 90 × 40 = 3600. If the mill standard is 3800, the lot is below standard and the mixing or the spinning twist needs review; the count is confirmed separately by reeling and weighing.
Traps
Confusing Ne with tex; reporting SD where CV% is asked; testing unconditioned samples (standard atmosphere 20 ± 2 °C, 65 ± 2% RH); treating one instrument reading as the whole lot.