Degumming strips the sericin; bleaching whitens what remains. Both can be run separately or combined in a single bath. Eri’s low sericin content (11–13 %) means the loss is modest — but pushing the alkali higher to work faster costs fibre strength that cannot be recovered.
Standardised recipes
| বিৱৰণ | Degumming | Bleaching | Single-bath degum and bleach |
|---|---|---|---|
| Material : water | 1 : 30 | 1 : 30 | 1 : 30 |
| Soap | 5 gpl | — | 5 gpl |
| Soda ash | 1 gpl | 0.5 gpl | 0.5 gpl |
| H2O2 (30 %) | — | 6 gpl or 20 cc | 6 gpl or 20 cc |
| Sodium silicate | — | 1.5 gpl | 1.5 gpl |
| Duration (minutes) | 60 | 60 – 90 | 60 – 90 |
| Temperature | 90 – 95 °C | 85 – 90 °C | 90 – 95 °C |
Follow with a hot wash at 60 °C for 5 minutes and a cold wash at room temperature for 5 minutes.
Alkali strength and tenacity
Sodium carbonate above 10 % and prolonged boiling raise degumming loss and cut
single-fibre tenacity. Ten per cent sodium carbonate with 10 % neutral soap for
one hour degums both white and red eri uniformly without tenacity loss. Traditional
practice — cocoon : water 1 : 1.5 with 10–15 % soda for 30–45 minutes
— remains in use at household scale.