| Solution A | { | Crystals of nitrate of silver | 90 | grains | } | Dissolve. |
| { | Distilled water | 4 | ounces | } | ||
| Solution B | { | Potassa, pure by alcohol | 1 | ounce | } | Dissolve. |
| { | Distilled water | 25 | ounces | } | ||
| Solution C | { | Milk-sugar (in powder) | ½ | ounce | } | Dissolve. |
| { | Distilled water | 5 | ounces | } |
Solutions A and B will keep, in stoppered bottles, for any length of time; Solution C must be fresh. To prepare sufficient for silvering an 8 in. speculum, pour two ounces of Solution A into a glass vessel capable of holding thirty-five fluid ounces. Add, drop by drop, stirring all the time (with a glass rod), as much liquid ammonia as is just necessary to obtain a clear solution of the grey precipitate first thrown down. Add four ounces of Solution B. The brown-black precipitate formed must be just re-dissolved by the addition of more ammonia, as before. Add distilled water until the bulk reaches fifteen ounces, and add, drop by drop, some of Solution A, until a grey precipitate, which does not re-dissolve after stirring for three minutes, is obtained; then add fifteen ounces more of distilled water. Set this solution aside to settle; do not filter. When all is ready for immersing the mirror, add to the silvering solution two ounces of Solution C, and stir gently and thoroughly. Solution C may be filtered.
The mirror should be suspended face downwards about ½-inch deep in the liquid, by strings attached to pieces of wood fastened to the back of the mirror with pitch, and before being immersed should be cleaned with nitric acid and washed with distilled water. The silvering is completed in about an hour, and when finished the surface should be washed in distilled water and dried, and then polished with soft leather, finishing with a little rouge.
The following method is used by M. Martin:—
Make solutions:
| 1. | Nitrate of silver | 4 | per cent. | ||
| 2. | Nitrate of ammonia | 6 | per cent. | } | perfectly free |
| 3. | Caustic potash | 10 | per cent. | } | from carbonates. |
4. Dissolve twenty-five grammes of sugar in 250 grammes of water; add three grammes of tartaric acid; heat it to ebullition during ten minutes to complete the conversion of sugar; cool down, and add fifty cubic centimetres of alcohol in summer to prevent fermentation, add water to make the volume to ½ litre in winter and more in summer.
Clean well the surface of the glass.
Take equal quantities of the four solutions: mix 1 and 2 together, and 3 and 4 also together: mix the two, pouring it at once into the vessel where the silvering is to be done. The mirror is suspended face downwards in the liquid, and the deposit begins after about three minutes, and is finished after twenty minutes. Take out the mirror, clean well with water, dry it in the air, and rub it then gently with a very fine leather.