Silk Reeling, Spinning and Post-Cocoon Technology
Domain focus
Post-cocoon technology covers stifling, drying, cooking, reeling and spinning. The exam tests the purpose of each step, reeling calculations and the difference between mulberry reeling and non-mulberry spinning.
Core rules and concepts
- Sort cocoons and remove defective ones. Stifle the pupa with hot air or steam to prevent emergence; dry cocoons to a safe moisture level for storage.
- Cooking softens sericin so filaments can unwind. Reeling is done in hot water; temperature and water quality affect breaks and yarn quality.
- Charkha reeling is a cottage method; filature and multi-end reeling produce more uniform raw silk. The number of ends and reeling speed must be controlled.
- Renditta is kilograms of cocoons needed for one kilogram of raw silk; a lower renditta means better efficiency. Reeling recovery is the inverse idea expressed as a percentage.
- Non-mulberry cocoons such as eri and tasar are often spun after carding because their filaments are discontinuous or hard to reel.
Worked example
A lot of 400 kg cocoons yields 40 kg raw silk. Renditta = 400 ÷ 40 = 10. If improved handling raises raw silk to 50 kg from the same cocoons, renditta = 400 ÷ 50 = 8. Reasoning: renditta is cocoon input divided by silk output; improving recovery lowers renditta and raises income per kg of cocoons.
Traps that cost marks
Inverting renditta; confusing stifling with cooking; using cold water for reeling; reeling tasar as if it were mulberry; counting cocoon weight after drying as fresh weight.