Pretreatment
The animal skin is removed from the epidermal layer, and the dermis layer is taken, first immersed in lye to remove keratin and other soluble components, and then washed with water and acid soaked to swell it.
Extrusion molding
The swelling skin is cut into strips and then cut into small pellets, which are mechanically beaten into a paste (glue), the solid content is adjusted, and the extruder is extruded into a tube through a special nozzle.
Fixed, dry
After dry styling (direct hot air drying) or wet styling (first coagulation in a coagulation bath, then hot air drying), then cross-linking with a cross-linking agent, drying, and cutting to make finished collagen casings.