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520 History of Three-Color Photography
This was to be used for 2J/2 minutes at 18° C. for correct exposure. The reversing solution was :
Potassium permanganate 2 g.
Sulfuric acid 10 ccs.
Water 1000 ccs.
This should be allowed to act for 3 or 4 minutes, the plate washed for about half a minute in running water, and then redeveloped with the same developer. After 3 or 4 minutes, when the high lights are completely darkened, the plate should be washed for 3 or 4 minutes and dried, without fixing. If after redevelopment the plate lacked brilliancy, it might be intensified with the acid-silver method.
Lumiere & Seyewetz40 also suggested the following method of using their metoquinon developer, although it seems to have been primarily suggested to them by M. Meugniot. The method is based on the first appearance of the image in a very dilute developer, and then finishing development with a concentrated solution, the duration in the latter being equal to the time of appearance of the image. The more concentrated stock solution (see p. 519) is used and 10 parts diluted with 15 parts of water. The plate should be placed therein, and the number of seconds counted till the first appearance of the image. The dilute developer should then be poured away, the stronger applied and development continued for the same time as that of the action of the dilute. It was stated that by this method exposures from correct to 4 times correct gave excellent results. The metoquinon here mentioned is a patented compound of two molecules of hydroquinon with one molecule of metol.
In place of the somewhat expensive metoquinon, R. Xamias 41 suggested the following:
Metol 4 g.
Hydroquinon 12 g.
Sodium sulfite, anhydrous 50 g.
Ammonia, sp. gr. 0.920 33 ccs.
Potassium bromide 6 g.
Water 1000 ccs.
This was found to act the same as Lumiere's developer and gave great brilliancy.
A. B. Hitchins42 recommended the following:
Metol 6.5 g.
Hydroquinon 2.10 g.
Sodium sulfite, anhydrous 40 g.
Potassium bromide 2.5 g.
Hypo 0.10 g.
Ammonia, sp. gr. 0.880 20 ccs.
Water 1000 ccs.
For use dilute with an equal volume of water. The small quantity of hypo caused the image to begin to reverse in this solution. Development should be carried on till the high lights or flesh tones just begin to show reversal,