Lay the glass flat on a cloth, and rub the surface carefully with a tuft of cotton-wool dipped in the Tripoli; then, before the cream dries, wipe it off with a second tuft, and polish with a third. Lastly, breathe upon the glass, and having ascertained that it is chemically clean, apply the Collodion.
Coating with Collodion.—Choose a rather thin Collodion which adheres tightly to the glass. A preparation which has been kept a long time after iodizing will usually answer the purpose very well, and, as a rule, a non-contractile, structureless Collodion is better than one which is glutinous and wavy. The degree of sensibility of the Collodion is not thought to have much influence upon the result.
Coating the Plate.—Apply the Collodion in the usual manner, and allow it full time to set perfectly, before dipping in the Bath, in order to favour its adherence to the glass. With Collodion prepared from anhydrous spirits, about half a minute may be given in cool weather.
The Nitrate Bath.—Take of
| Fused Nitrate of Silver | 40 | grains. |
| Glacial Acetic Acid | 30 | minims. |
| Alcohol | 20 | minims. |
| Water | 1 | fluid ounce. |
Saturate with Iodide of Silver as described at [page 204], and filter. An immersion of one minute will be sufficient; after which, give the plate an up-and-down movement, and wash it in plain water, in the manner advised for the Oxymel preservative process, at [page 292]. Then stand it on blotting-paper, to drain for a minute or two, wipe the back of the glass, and pour on the Albumen.
This Bath may become discoloured after a time; continue to use it until it is of a dark sherry-colour, and then treat it with "Kaolin," in the manner and with the precautions advised at pages 91 and 245.
The Iodized Albumen.—Procure eggs, fresh laid, or not more than two or three days old. Separate the whites in the same way as for Albuminized paper ([p. 241]), and mix by the following Formula:—
| Albumen | 9 | fluid ounces. |
| Water | 3 | fluid ounces. |
| Liquor Ammoniæ | 2 | fluid drachms. |
| Iodide of Potassium | 48 | grains. |
| Bromide of Potassium | 12 | grains. |