This is a more rapid developer than the preceding. The print is fixed in like manner by water, in which it must be well washed, and afterwards dried. When dried by artificial heat, the vigor of the print is increased. Prints that have been developed by the solution of nitrate of silver may be immersed in the gold bath, which improves their tone.
The picture may be developed, also, by immersing the prints in a saturated solution of bichloride of mercury and afterwards in one of nitrate of silver. In this case, however, the times of exposure must be increased.
Pictures may be obtained, also, by floating the papers on a mixture of equal quantities of nitrate of silver and nitrate of uranium in about six times their weight of water.
When dry, they are exposed beneath a negative. In this case the image appears, as in the positive printing process, with chloride of silver, being effected by the decomposition of the nitrate of uranium, which, reacting on the nitrate of silver, decomposes this salt and reduces the silver. These prints require fixing in the ordinary bath of hyposulphite of soda, and then washing, as usual.
Float the papers for four minutes in the preceding bath of nitrate of uranium, drain and dry. Next, expose beneath a negative for eight or ten minutes, then wash and immerse in a bath of
Ferridcyanide of potash.......30 grains.
Water...................... 3 ounces.
In a few minutes the picture will appear of a red color, which is fixed by washing thoroughly in water.
Immerse the red picture, before it is dry, in a solution of
Sesqui-chloride of iron.......... 30 grains.
Distilled water................. 3 ounces.
The tone will soon change to green; fix in water wash and dry before the fire.
Float the paper for three or four minutes on a bath of:
Water........................ 2 ounce's.
Nitrate of uranium..............2 drachms.
Chloride of gold................2 grains.
Afterward take them out and dry. An exposure of ten or fifteen minutes will cause the necessary reduction; the picture has a beautiful violet color consisting of metallic gold. Wash and dry.