Fundamental Factors in Rapid Processing

Abstract

Shortening of the time of photographic processing may be desired to minimize delay before the resultant image can be used, to reduce the size of equipment, or to increase its productivity. Processing rate can be increased by the choice of sensitive materials of inherent high response to the action of processing baths, and by the use of highly-active baths at elevated temperatures. In some processes, the washing, or both the fixing and washing stages, may be eliminated.

In all steps involving developing, fixing, washing, and drying, it is important to assure a continuous supply at the emulsion surface of fresh, fully-active solution, while removing the slower-acting used solution. The highest possible gradients for mass and heat transfer are desired and are obtained when quiescent fluid surface films are kept at minimum thickness by mechanical means or by turbulence. Processing is thus accelerated by intensive agitation of baths, spray application of wash water and chemical solutions, and by impingement drying. Washing is also accelerated by the use of chrome alum in preference to aluminium hardening baths, and by the use of washing “aids”. Typical rapid-processing equipment is illustrated.