Float the paper upon the following solution for three minutes and hang it up to dry:
| Uranium nitrate | 30 to 60 parts |
| Silver nitrate | 8 parts |
| Water | 100 parts |
The sensitiveness increases in proportion to the quantity of uranium nitrate. With the above formula the paper can be exposed in the camera, or, for printing, under a negative cliché.
In printing an exposure of five seconds in diffused light gives an image perfectly visible, and a grayish black tone; ten seconds gives a vigorous image almost of a black color; in from fifteen to twenty seconds the image is very strong, with the color of an engraving. In sunshine the action is necessarily much more rapid.
The impression is developed by immersion in
| Ferrous sulphate | 8 parts |
| Tartaric acid | 4 parts |
| Sulphuric acid | 1 part |
| Water | 100 parts |
The image is rapidly developed. It is fixed by washing in water.
DE LA BLANCHERE'S PROCESS (1858).
| Uranium nitrate | 25 parts |
| Distilled water | 100 parts |
Filter the solution and keep it in the dark.