| Gelatine (Nelson’s) | 2 | ounces. |
| Water | 20 | ounces. |
Put the above into a wide-mouthed bottle or jar, and allow the gelatine to soak until soft; then place the vessel in a large saucepan containing cold water, and set on a fire, or over a gas-burner, and by the time the water in the saucepan is hot the gelatine will be dissolved. Then add slowly (stirring the gelatine with a glass rod) one drachm of a ten-grain solution of chrome alum. Now strain the gelatine solution through fine muslin into a clean dish, standing it in a larger dish containing hot water; float the bank post paper upon this solution (taking care to avoid air-bubbles) for two minutes, then lift it off slowly and hang it up to dry, pinning it by two corners to the edge of a shelf.
When dry, the operation is repeated, but this time the paper is hung up to dry by the two opposite corners, so as to equalize the coat of gelatine.
When dry a second time, it must be floated for two minutes upon
| White of | 5 | eggs. |
| Water | 13 | ounces. |
(Shake up well, and filter into a cold dish.)
Paper prepared as above will keep for any reasonable length of time.
For use, it is drawn slowly through a solution composed of
| Bichromate of Potash | 1 1⁄2 | ounces. |
| Water | 20 | ounces. |
| Alcohol | 5 | ounces. |
| Liquor Ammonia | 10 | minims. |
This being done, the paper is again hung up to dry, this time in a dark room.