Gravimetric Yarn Count Measurement
topic
Gravimetric yarn count determination (ISO 2060) reels precisely measured yarn lengths using a wrap reel (1.0 m or 1.5 m perimeter, SDL Atlas YG023, Zweigle, electronic counter ±1 revolution) and weighs skeins on calibrated analytical balance (±0.1 mg) after conditioning at 20°C/65% RH for minimum 4 hours (ISO 139). Procedure: reel 10 skeins of 100 m each from same package, condition 4 hours, weigh each skein to 0.1 mg, calculate tex = skein mass (mg) / 100, Ne = 590.5 / tex. Statistical requirement: mean of 10 skeins, SD, CV%, and comparison against specification — CV% < 2.0% indicates uniform winding tension and consistent spinning; CV% > 3.5% diagnoses drafting autoleveller malfunction or package density variation. Moisture correction (if conditioning time is insufficient): Wdry = Wactual / (1 + actual regain / 100) × (1 + standard regain / 100) — cotton standard regain 8.5%, wool 17.0%, polyester 0.4%, nylon 4.5% (ISO 6741-1 standard regain values). Count conversion factors: Ne × 0.5905 = tex; Nm × 1.0 = tex⁻¹ × 1000; denier = tex × 9; dtex = tex × 10. Commercial count tolerance: ring-spun cotton ±3% CV, open-end ±2.5%, filament yarn ±1.5% — tighter tolerances for weaving warp yarn (±2%) versus knitting (±3%) due to differential tension sensitivity. Bundle count (ISO 7211-5, count of yarn removed from woven fabric): cut 10 cm warp yarn samples, unravel 10 threads, weigh together to calculate count — method for verifying fabric as-woven count versus specification.
Role
Gravimetric count determination is the legally recognised and highest-accuracy method for yarn linear density measurement, providing the certified count values used in commercial purchase contracts, customs classification (fabric weight/m² calculations), and dye recipe preparation — the 4-hour conditioning requirement making it the deliberate but definitive quality verification test whose results override all online measurement shortcuts.