| Gelatine | 27 | g. |
| Water | 400 | ccm. |
| Bichromate of potassium | 9 | g. |
| Preparation A | 15 | ccm. |
| Preparation B | 15 | ccm. |
| Ammonia a few drops. |
The preparations A and B are as follow:
| A.— | Chloride of sodium | 1 | g. |
| Water | 500 | ccm. |
| B.— | Sulphate of alumina | 1 | g. |
| Water | 100 | ccm. |
To each square decimetre of surface should be allowed 2 ccm. of the above solution. The plates are replaced in the drying box, which is heated to 45° or 50° C. They should be dry in three hours, and are then ready for printing under a negative in the copying frame. They are afterwards well washed in filtered water, and allowed to dry spontaneously in a dust-proof situation. In two or three days the printing may be proceeded with, the surface having been softened by allowing the plate to stand for seven hours in the following solution—
| Glycerine | 500 | ccm. |
| Distilled water | 200 | ccm. |
| Preparation C | 100 | ccm. |
| Preparation C.— | Sulphate of magnesia | 50 | g. |
| Distilled water | 500 | ccm. |
All solutions are filtered through flannel. From the face of the plate the superfluous moisture should be removed with a sponge. A very thick glass plate is fixed to the face of a lithographic stone by means of glue and whiting, and adhesion is secured between the face of the thick glass plate so fixed and the back of the Collotype plate by means of a few drops of water. The whole, so arranged, is placed upon the bed of the press. Should the prints lose their contrast while the printing is in progress, they are lightly sponged over with a sponge dipped in the last-mentioned solution. If this fails to produce sufficient effect, the plate is first washed with turpentine, and then with the glycerine solution. Care should be taken to prevent the two liquids becoming mixed on the plate, to prevent which different sponges and drying cloths should be used.
CHAPTER XI.