Colouring.—Usually a cheap water colour only is required; a light coating of a cheap varnish may be sufficient. In other cases a water colour serving as a filler for smoothing the surface may receive a finish of one or more coats of resinous solutions in alcohol or of copal varnish. Many goods are coated with asphaltum or Japan varnish and dried in cold or hot air.
Some of the articles may be decorated with scrolls or arabesques in oil colours or enamels, or the lines may be covered with bronze powder, or with metal, gold, or aluminium leaf.
Varnishing.—The following varnish recipes are suitable:—
| (1) | (2) | (3) | (4) | ||||
| Shellac | 20 | Shellac | 10 | Shellac | 6 | Sandarac | 15 |
| Alcohol | 70 | Rosin | 10 | Sandarac | 3 | Mastic | 5 |
| Lamp black | 10 | Alcohol | 60 | Mastic | 18 | Turpentine | 5 |
| Lamp black | 20 | Alcohol | 73 | Alcohol | 75 | ||
| 100 | 100 | 100 | 100 | ||||
[CHAPTER VIII]
CHEMICALS USED IN PAPER-MAKING
The manufacture of paper is a highly technical industry, which requires a practical knowledge of mechanical engineering, as well as an intimate acquaintance with the many important chemical problems connected with the art.
The following brief description of the various chemicals used in the manufacture of paper is divided into certain classes, based upon the order of the operations through which the raw material passes before its final conversion into paper:—
(1) The alkaline processes used for treating raw fibre: soda ash; caustic soda; lime; recovered ash.