First lye boil with soda ash and caustic soda.
Second lye boil. For some classes of goods no less than six lye boils may be required.
Grass between lye boils (according to their number).
Rub with rubbing boards. This is also a speciality in linen bleaching, and consists of a mechanical treatment with soft soap, the object of which is to remove black stains in the yarn.
Bleach with hypochlorite of soda.
Scald. The two latter treatments are repeated three to five times, each series constituting a “turn.” Grassing intervenes between each turn, and in some instances the pieces are rubbed before the last soda boil.
| Fig. 9.—Diagram showing the Horizontal Drying Machine threaded with Cloth. |
The pieces are next steeped in large vessels (kiers) in weak hypochlorite of soda, and then in weak sulphuric acid, these treatments being repeated several times.
Ultimately the goods are mill-washed, blued with smalt and dried.
Bleaching of other Vegetable Textile Fabrics.