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20 IVES AND KUNZ July
velopers, the relation between features of design of a chemical recirculation system affecting aeration, and the economics of the developing agent and sulfite consumption have been studied by G. I. P. Levenson.15 He concludes that serious losses can occur when air is introduced into a developer by spraying or other means, especially if the volume of developer in a recirculation system is large. His findings indicate the desirability of extremely small circulatory systems relative to the rate of film handling, as exemplified by the spray developing unit described in the present paper.
Effect of Temperature Elevation
As stated by Crab tree,13 the rate of development generally increases by a factor of about 2 for each 15 F rise in temperature. The acceleration of fixing by elevation of temperature is much less. Washing of film can be speeded up greatly by rapid renewal of water at the film surface but the influence of temperature elevation, while favorable, requires further study. Unnecessarily high temperature of the wash water should be avoided, both to prevent swelling and softening of the gelatin emulsion and to economize power in water heating. The effect of temperature variation in rapid processing has proved to be about the same per degree as in conventional 70 F processing.
Quality of Rapidly Developed Images
Up to the present time, no systematic study has been made of the effect of rapid processing on the structure of the developed silver image to discover the effect on resolution, graininess, etc. However, observation on images developed, fixed, washed and dried in times of 5 to 10 sec, respectively, by projection and in photomicrographs has shown little that is unusual. In certain cases, evidence has been obtained of incompleteness of treatment near the bottom of the emulsion layer with a development time of 5 sec even though the emulsion speed and quality were about normal. This deficiency has been found to increase when the treating time was reduced to 1 second, for example, especially if the compensatory adjustments in developer activity and temperature were not sufficient to assure normal completeness of development. The use of elevated temperatures appears to offer no promise of a significant increase in emulsion speed nor of improvement in graininess. Anyone contemplating the use of hightemperature processing with the softer types of emulsion should make sure that the supplementary hardening in processing is always ample so that graininess will not be produced as a result of incipient reticulation.