The Dictionary Of Photography

A True Historic Record Of The Art & Practice Of Photography 100 Years Ago.

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Platinotype
print should be thoroughly washed and then fixed in hypo, and well washed to free it from any soluble silver salt. The intensified print can afterwards be toned with gold or platinum to obtain different tones. Platinotypes may also be toned with uranium by the following process suggested by Hubl: -
A.
Uranium nitrate ............      48 grs.
Glacial acetic acid...... ... ...      48 .. •
* Water           ............... 1 oz.
B. Potassium ferridcyanide (ferricyanide) ... 48 grs. Water           ... ...... ...... 1 oz.
C.
Ammonium sulphocyanide...... ... 240 grs.
Water           ............ ... 1 oz.
For use, add to 1,000 parts of water 10 parts of the above solu-tions one after the other. The well-washed platinum print should be placed in a dish and covered with the solution, and the dish rocked till the desired tone is attained. The toning bath should then be poured away, the prints washed in frequently changed water. The process of toning is complete in about five minutes, and with concentrated baths takes place so quickly that it is impossible to avoid failure. In place of the sulphocyanide, sodium sulphite may be used, but as this acts more energetically the bath must be more dilute. For this should be used 5 parts of A and B and 5 parts of a 10 per cent, solution of sodium sulphite to 100 parts of water. Grape sugar acts very slowly and thiosinamin very quickly. Platinotypes may be toned in a similar manner to the above, with ferridcyanide of iron, and blue tones be obtained which are suitable for moonlight and night scenes. With this process sodium sulphite is less suitable. The following solutions should be used :
A.
Ammonium iron alum ..          ... ...      48 grs
Hydrochloric acid...... ... ...      48 ,,
Water           ...............      10 oz.
5*4