The Dictionary Of Photography

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

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Harmonising Harsh Negatives
Bichromate of potassium ... ... ... 10 grs.
Bromide of potassium ... ... ... 5 ,,
Water           ...... ... ... ... 1 oz.
Bathe the plate and allow the solution to permeate the film. Pour the solution off and add to it five drops of nitric acid. Again flood the plate and the image will be converted into bromide of silver. Allow the action to proceed through the film. Bathe in three changes of alum, a 5 per cent, solution of potassium metabisulphite, to remove the bichromate and harden the film, and wash thoroughly in water. As the opera-tions are carried out in white light, such as that of gas or a lamp, the plate is amply exposed by the time the washing is completed. The following pyro developer was found quite suitable. Any preservative may be used, but as there is nothing on the plate but the image to be affected by the de-veloper, there is no necessity to use a bromide. A small trace may be useful to control development, but if any bichromate of potassium remains in the film it will unite with the bromide, and convert the image back into bromide of silver as fast as it developed.
Pyro..................2 grs.
Ammonia ... ... ... ... ... 2 mins.
Bromide of potassium (if used at all) ... gr.
As the shadow detail lies on the surface it will first be developed, the half-tone will follow, and the high lights will remain white when viewed from the back of the plate for some time. As the surface of the film will veil over as soon as the developer begins to act, the progress must be judged entirely from the back of the plate. The only judgment required in the process is in stopping the development at the right time. If stopped too soon, the negative will be flat; if carried too far, the negative will still be hard. Mr. Mcintosh says: " It will be well to have ready for reference a print from the negative in which the shadows have been printed to their proper depth. When the lightest half-tone which shows in the print is nearly, but not quite, blackened through by the developer, on viewing the plate from the back the action should be stopped, the plate washed and transferred to the hypo, which will speedily dissolve out the undeveloped silver
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