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522 History of Three-Color Photography
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B. Potassium bromide 10 g.
Boric acid 50 g.
Water 1000 ccs.
In the second dish was the developer and in the third the reversing solution. The plate was placed, in absolute darkness, in the first dish and left for 2 minutes ; the dish should be covered and the red light turned on. The developer was the usual metoquinon diluted with eight times the quantity of water. The plate should be well rinsed after the desensitizing bath and immersed in the developer for 10 or 15 minutes, or till it appeared grey, then washed and immersed in the reversing bath. As soon as the negative image had entirely disappeared, the plate was rinsed for a minute, then redeveloped.
E. Cousin55 advised soaking the plates in water before applying the developer, so as to soften the gelatin and enable it to act better on the lower layers of the emulsion, where the image actually lies ; he stated that this method enabled plates to be developed without fog setting in. Apparently as one would expect almost any developer can be used, such as pyrocatechin, rodinal, amidol, pyro-metol, etc. C. Simmen56 strongly recommended the acid amidol developer, his formula being :
Diaminophenol (amidol) 6.6 g.
Sodium sulfite, anhydrous. 19 g.
Sodium bisulfite lye 19 ccs.
Potassium bromide, 10 per cent sol 19-33 ccs.
Water to 1000 ccs.
The bromide might be reduced, only enough being used to keep the whites clean. The great advantage of this developer was said to be that it begins to develop from the bottom of the film, where the most exposed grains lie.57 The solution, as given above, will not keep, and therefore, it is better to make a stock solution of sulfite and add the amidol as wanted.
A committee of the Scciete Francaise de Photographie5S reported that while acid amidol gave good results, the plates were less brilliant than when the Lumiere pyro developer was used, and the latter was on the whole preferable. Amidol was strongly commended by G. Balagny,5y H. D'Arcy Power,60 A. Personnaz,61 R. Espitallier6' and others.
F. Dillaye63 advised immersion of the plate in bromide and acid sulfite, followed by development with metoquinon. For developing Autochromes in the tropics, G. de Vies64 recommended :
Pyrogallol 4 g.
Potassium bromide 4 g.
Sodium sulfite, anhydrous 20 g.
Acid sulfite lye 1-2 drops
Ammonia 30 ccs.
Water 1000 ccs.
The plate should be first treated with a 2.5 per cent solution of formaldehyde, and then rinsed for 10 seconds.