“The solutions recommended by Mr. Common are three:
| (1) | Nitrate of Silver | 1 | ounce. |
| Distilled Water | 10 | ounces. | |
| (2) | Caustic Potash | 1 | ounce. |
| Distilled Water | 10 | ounces. | |
| (3) | Glucose | 1⁄2 | ounce. |
| Distilled Water | 10 | ounces. |
The above quantities are suitable for 250 square inches, consequently, an ordinary copy mirror 8 × 6 would require rather more than two ounces of each solution, and other sizes in proportion.
The caustic potash and distilled water must be quite pure. Ordinary caustic potash will not answer at all. The best to use is known as pure by alcohol.
The glass surface to be silvered is carefully cleaned with strong nitric acid, applied, as recommended by Mr. Browning, with a Buckle’s brush, then well {37} washed in clean water, and after rinsing with distilled water, laid, face downward, in a dish of distilled water until wanted.
Before cleaning the glass, it will be necessary to arrange for supporting it face downward in the depositing dish, so that the surface to be silvered may be quite horizontal, and just below the level of the fluid, which should be about half an inch above the bottom of the dish.
I have generally used a large cork, about four inches in diameter, cemented to the back of the plate, and fitted with three strings, by which it could be suspended in a level position and adjusted to any height by winding the string over a roller placed at a convenient height above the dish. When this arrangement is not available, I fix on the back of the plate two ordinary wide-mouthed bottle corks of equal thickness, in the positions shown in the figure, and to these corks attach thin slips of bamboo running transversely across the plate, and of sufficient length to rest on the sides of the dish, thus:
Fig. 3.
The slips of bamboo give the arrangement a certain amount of spring, by which the height of the plate can easily be regulated, by putting on weights until the surface of the plate is just below the level of the fluid in the dish.