Post-Cocoon Technology

Post-cocoon technology covers everything that happens between the harvested cocoon and the finished yarn: stifling, drying, cooking, reeling or spinning, degumming, blending and packaging — together with the economics that decide whether any of it pays. Muga and eri part company at the very first step. Muga has 150–250 m of continuous filament and is reeled; eri’s open-mouthed cocoon yields only a few centimetres of unbroken filament and must be spun. Almost every difference downstream follows from that one fact.

40–45 %Muga raw silk from shell weight

~50 %Same, using SILKPLUS

80–85 %Of muga still reeled on the bhir

13–16 %Eri degumming loss

Cocoon to yarn — the two routes

Muga — reeled

1 Stifle & dry115–95 °C, 2 hours to stifle; to 60 % driage for storage

2 CookSodium carbonate 2.0–2.5 g/L at 95 °C, or Muga Super Cook at 2 g/L

3 ReelWet basin 50–60 °C; 8–10 cocoons for warp, 12–14 for weft

4 Re-reel & pack150 cm reel, then 2 kg and 5 kg books

Eri — spun

1 Extract pupaAfter the moth emerges, or the pupa is removed for food or seed

2 Degum1 : 30 liquor, soap 5 gpl, soda ash 1 gpl, 60 min at 90–95 °C

3 Make cakeSheets stretched, joined and stamped into a pad, dried to 20 % moisture

4 SpinTakli, flyer machine, or CSTRI motorised at 4,500 rpm

Hover a plate to lift it flat. The two chains never converge: muga holds 150–250 m of unbroken filament and can be unwound, eri holds a few centimetres and cannot. Every difference below follows from that one fact.

Muga cocoon processing

Stifling and drying to arrest the pupa, cooking to soften the sericin, reeling on the traditional bhir or the improved reeling-cum-twisting machine, then re-reeling and packing.

Stifling & Drying
Temperature, duration and driage for stifling only, medium drying and full drying.
Cooking & Degumming
Laboratory and field recipes, SILKPLUS and Muga Super Cook, eri degumming.
Reeling
Warp and weft denier, bhir against the CSTRI reeling-cum-twisting machine.
Packaging & By-grade Yarn
Re-reeling, hanks and books, and ghicha from non-reelable cocoons.

Eri silk spinning

Eri cocoons are spun after the pupa is removed for consumption or seed, or after the moth has emerged — which is why eri is ahimsa silk. Spinning is concentrated in Palasbari, Bijoynagar, Goalpara, Kokrajhar and Udalguri in Assam, and most of the yarn is consumed within the state.

Fibre Properties vs Mulberry
Density, fineness, tenacity, modulus, elongation, moisture regain, degumming loss.
Degumming & Bleaching
Three standardised recipes, plus the household practice still in use.
Hand Spinning
Cake preparation, and the takli, flyer and CSTRI motorised machines compared.
Mill Spinning
The eight-stage worsted route from degumming through ring spinning to gassing.
Blends & Market Position
Eri with wool, acrylic, cotton, bamboo and polyester — and where each performs.

Fibre, by-products and economics

Silk Fibre Properties
Muga, eri, mulberry and tasar compared across eight physical properties.
By-products
Pupa, pupal oil, sericin, castor seed, seed cocoon, ghicha and spun grades.
Economics of Muga Culture
Full cost and return structure for one acre of som plantation, 2025-26 prices.
Economics of Ericulture
Castor-based ericulture on one acre, four crops, 400 dfls.
Comparative Metrics
Muga and eri side by side — and why the two B:C ratios are not comparable as stated.
Yarn & Cocoon per Product
What a saree, kurta, jacket or stole actually consumes.
Eri Fabric & Products
Mufflers, stoles and shirting by specification, count and price.
Eri Yarn Slab Rates
Fourteen counts across ten order-quantity slabs.
Glossary of Terms
Every term used across these pages, from bave and bhir to NBFL and SR.