The Dictionary Of Photography

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

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Platinum Toning
essential for successful work. The prints, whether on gelatino-chloride, plain salted, or smooth or rough surface paper, need not be printed any deeper than usual. The platinum salt em-ployed should be the chloro-platinite, the ordinary perchloride being comparatively useless for this purpose. The print must be absolutely freed from soluble silver salts before toning, the toning bath must be acid, and the paper must be free from all acid and soluble platinum salts before fixing, or else the whites become yellowed. To free the print from silver nitrate the best thing to do is to allow it to soak for five minutes in a solution of salt and water 2 ozs. to the pint, and then wash so as to free it from excess of salt, and then place in the toning-bath. Numerous formulae have been suggested for this, but the most suitable are either that of Stieglitz, which is -
A.   Oxalate of potash ... ...... ... 256 grs.
Acid phosphate of potash ... ... ... 128 ,,
Distilled water ... ... ... ... 5 ozs.
B.  Chloroplatinite of potash ... ... ... 60 grs.
Distilled water ............ 2 ozs.
For use take of
Solution A.............. ... 3 parts.
Solution B. ... ... ... ... ... 1 ,,
Distilled water ... ... ... ... 2 ,,
This can be brushed over the well-washed print. A far simpler bath is obtained by using the chloro-platinite with an acid or acid salt, and provided nitric or hydrochloric acid is not used there is not much difference to be detected. If a faintly acid and somewhat weak bath be used, such as is obtained by using a saturated solution of cream of tartar, warm sepia tones are obtained, whereas, by using stronger acids, such as phosphoric or citric and a greater concentration of bath, deeper tones are obtained.
No. 1 for Sepia Tones.
Acid tartrate of potash (cream of tartar) ...      60 grs. Potassium chloroplatinite ... ... ... 1 ,,
Distilled water          ... ... ......        6 ozs.
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