Esparto Pulp.—The first process in the manufacture of the paper is cleaning. The bundles of grass are opened up, shaken out, and put through a willowing machine. This consists of a hollow conical drum, the outer surface of which is a coarse wire cloth. Inside the drum is fitted a shaft provided with wooden teeth, and as the grass passes through it is tossed about and the dust removed. The clean grass is conveyed by travelling belts to the digester house. For the production of a high-class paper the grass is often examined by girls, who stand on either side of the travelling conveyer and take out any coarse root ends and foreign material not removed by the willowing machine.
Boiling.—The object of submitting esparto to chemical treatment is to obtain a pure paper-making fibre known as cellulose. The composition of this raw material is shown by the following analysis:—
Spanish Esparto.
| Cellulose | 48·25 | |
| Water | 9·38 | |
| Aqueous extract | 10·19 | |
| Pectous matter | 26·39 | |
| Fatty matter | 2·07 | |
| Ash | 3·72 | |
| 100·0 | ||
| Yield of dry cellulose obtained in actual practice from good raw material | 45 to 48 % | |
By boiling the esparto with caustic soda under pressure for a stated time, the non-fibrous constituents are removed, leaving the cellulose in a more or less pure form according to the severity of the chemical treatment.
Fig. 20.—An Esparto Duster.