The Dictionary Of Photography

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

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Platinotype
be kept after development for some weeks, or even months, before toning, but very old prints will not readily tone. If the weather is cold, the water and dishes used will probably require to be slightly warmed or the action will be very slow. Prints are best toned in good daylight, as it is easier to see that the gold is kept evenly distributed over the print, and daylight also assists the action and renders the process more rapid than when performed by gaslight. The general effect of the toning action is to slightly increase the contrasts in the print, as proportion-ately more gold is deposited where there is a large quantity of platinum present than where there is a small quantity. The best results are obtained when the actual increase in intensity required is small only. The method of treatment I have described will, I think, be found to have four distinct uses: (i) To strengthen under-exposed prints ; (2) To convert a rusty or brownish colour in a print into a pure black ; (3) To produce blue-black in the place of black prints when this modification of colour is considered desirable; (4) To enable brighter prints to be obtained from flat negatives than is usually possible by the ordinary method. A method of intensifying platinotype with silver has also been suggested. For this either an acid pyro or acid hydroquinone developer could be used, to which a few drops of a 10 per cent, solution of silver nitrate had been added. The solutions required are,
1.  Pyrogallol ... Citric acid ... Distilled water
or,'
2.   Hydroquinone Citric acid ... Distilled water
3.   Silver nitrate Distilled water
2
grs.
20
»»
I
oz.
2
grs.
20
If
I
oz.
48
grs.
I
oz.
The prints after clearing must be thoroughly freed from acid and placed in a clean dish. Ten drops of No. 3 should be added to one oz. of either 1 or 2, and the solution, which turns white and cloudy, immediately applied to the print and the dish rocked. As soon as the desired degree of intensification is reached the
513                                 LL