Processing

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Sequence of chemical reactions that render an exposed image visible and permanent. 1

Black and white negative – positive processing

Basic steps:

  • Developer: The image is produced in the development step.
  • Stop rinse: This rinse stops the action of the developer retained in the film and brings the pH closer to that of the fixer..
  • Fixer: converts the insoluble silver halide remaining after development into soluble silver complexes.
  • Wash: removes fixer from the film surface and from within the emulsion.
  • Drying: lowers the water content in the emulsion and dries the film for windup and subsequent projection or printing. 2
  • h3. Colour processing

Basic Steps:

  • Prebath: The rem-jet anti-halation backing is softened.
  • Rem-jet Removal: the softened backing is removed and flushed away.
  • Developer: developed the exposed silver halide and reacts with the colour coupling agents in the film to create dye layers along with a silver image. (ECN-2, ECP-2)
  • Stop: stops the action of the developer carried over by the film.
  • Wash: removes excess stop bath.
  • Fixer: removes undeveloped silver halide from the emulsion.
  • Wash: removes excess fixer.
  • Persulfate Bleach Accelerator: prepares the film for action of persulfate bleach. (ECN-2)
  • Bleach: converts the metallic-silver image formed by the developer into silver halide again. (ECN-2, ECP-2)
  • Wash: removes excess bleach.
  • Sound-track Developer: converts the silver halide sound track area into metallic silver. (ECP-2)
  • Wash: removes excess sound track developer (ECP-2)
  • Fixer: removes silver halide formed in the bleach from the emulsion.
  • Wash: removers fixer from the film.
  • Stabilizer: stabilizes the dye images and promotes uniform drying.
  • Dryer: dries the film for windup and subsequent projection or printing. (Kodak)

 

Processing is one of the most important factors contributing to the ultimate permanence of photographic records. A thorough washing is particularly important because thiosulfate salts (hypo) left in the processed material can fade a silver image by converting it partially to silver sulfide, especially under conditions of high humidity and temperature. 2

 

References

1 Case, D., 1985, Motion Picture Film Processing, Media Manuals, Focal Press, London, Boston
2 Kodak: A Concise Glossary for the Non-Technician