Raw Silk Reeling and Grade Testing

Raw silk grading tests reelability, size variation, neatness, cleanliness, and cohesion under International Silk Association (ISA) standard conditions — water temperature 38–42°C, reeling speed 100–150 m/min, 8 or 10 filament ends combined to target 20/22 denier raw silk thread. Reelability test (ISO 2076 method): 100 cocoons soaked in 38°C water for 5 minutes, % that reel cleanly for >100 m without end break = reelability% (optimum >85% for Grade 3A; <70% indicates damaged or poorly reared cocoons). Size variation (denier CV% along 450 m reel, measured by electronic denier meter every 9 m): Grade 6A CV% <1.5%, Grade 3A <2.5%, Grade 1A <3.5% — size variation causes dye variation (barré) in woven fabric. Neatness score (visual inspection of 100 m reeled skein for loops, frizz, and double ends under standardised illumination, scored 0–100): Grade 3A ≥90/100. Cohesion (crimp count per 10 cm measured by standardised tension, minimum 40 crimps/10 cm for adequate yarn processing cohesion). Gum content (sericin% by weight, dried 105°C 2 hours): raw silk 22–28% sericin — laboratories verify gum content for trade settlement as raw silk price is calculated on a degummed basis with deduction for measured sericin content. Japanese JISFA 2019 raw silk standard divides quality into 6A (finest, >95 reelability), 5A, 4A, 3A (commercial benchmark), 2A, and 1A grades with price differentials of 20–40% between grades.