Automatic Film Processing

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Automatic Film Processing

• Film Transport
• Water System
• Recirculation
• Replenishment System
• Developing
• Fixing
• Washing
• Drying

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Film Transport

• A system of rollers that moves the film through
  the developer, fixer, washing and drying sections
  of the processor.
• Also acts as a squeegee action to remove excess
  chemicals from the film.

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Make up of the Transport System

• Entrance roller or detector roller
• Vertical or Deep racks (transport racks)
• Crossover assembly
• Squeegee assembly

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Entrance roller or detector roller

• Contains the Entrance rollers and guide shoes
  which moves film into the developer tank
• Also contains a micro switch which turn on the
  replenishment pump

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Vertical or Deep racks (transport racks)

• Moves film into and through solutions and dryer
• Uses a turn around assembly at the bottom of the
  tank to turn film direction upward.

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Crossover assembly

• Moves film form developer to fixer tank and from
  the fixer to the wash tank
• Forces solutions from film back into the tank it
  is coming from.

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Squeegee assembly

• Moves the film from the wash tank to the dryer
• Squeegee action removes excess water from the
  film.

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Water System

• Washing the film
• Temperature control

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Circulation or Recirculation or Filtration System

• Agitates developer solution
• Removes reaction particles by the use of a
  filtration system
• Helps stabilize developer temperature.
• Agitation and circulation
• Agitation keeps solutions in contact with a
  heater element in the bottom of the tank and
  prevents layering of chemicals
• Maintains developer temperature
• Heating element is controlled by a thermostat

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Replenishment or Regeneration Systems

• Responsible for replenishing processor solutions
  that are used during processing
• Consist of a series of umps, plastic tubing and
  plastic storage tanks.
• Replenishment is based on the length of the film
  processed.

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Types of Replenishment

• Volume Replenishment
• A volume of chemicals are replaced for each film
  that is processed.
• Flood Replenishment
• Periodically replenishes chemicals regardless of
  the number of films processed.

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Developing

• Changing the latent image of film to a visible
  image (manifest image) composed of minute
  clusters of silver.

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Components of the Developer

• Solvents
• Developing agents
• Accelerators
• Preservatives
• Restrainers
• Hardeners

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Solvents of the Developer

• Water is the solvent in the developer
• Water dissolves and ionizes the developer
  chemicals
• Film emulsion also absorbs water, causing it to
  swell. This allows the dissolved developing
  agents to penetrate the emulsion and to reach all
  the silver halide crystals.

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Developing or Reducing Agents

• This component oxidizes the silver and converts
  the latent image into the manifest image
• Two Components of Reducing Agents
• Hydroquinone - Slowly builds black tones for
  contrast
• Phenidone quickly builds gray tones

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Accelerators or Activator

• Composed of
• Sodium or potassium carbonate
• Sodium or potassium hydroxide
• Increase the rate of chemical reaction,
  converting exposed silver halide grains into
  metallic silver at a more rapid rate.
• Swells and softens the emulsion so that the
  reducing agents may work more effectively.
• Provides an alkaline medium for reducing agents

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Accelerators or Activator

• Must have a pH of between 10 and 11.5
• Must be alkaline

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Preservatives of the Developer

• Sodium or potassium sulfite
• Help maintain the rate of development and prevent
  staining of the film emulsion layer
• Also helps protect the hydroquinone from oxidation

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Restrainers or anti-foggers

• Potassium bromide
• Potassium iodide
• Protect unexposed silver halide grains from the
  action of the developer, minimizing film fog.

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Hardeners of Developer

• Glutaraldehyde
• Prevents excessive swelling of the gelatin and
  damage to the film as it passes through the
  rollers.

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Fixing

• Clearing of undeveloped crystals before washing
  to prevent discoloration of the film with age or
  exposure to visible light.

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Fixer Components

• Solvent
• Fixing agent
• Preservative
• Hardener
• Acidifier
• Buffer

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Solvent of the Fixer

• Water
• Diffuses into the emulsion, carrying with it the
  other dissolved chemicals of the fixer.

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Fixing or Clearing Agent

• Sodium thiosulfate and ammonium thiosulfate
• Dissolves and removes the undeveloped silver
  halide grains from the emulsion.
• This allows the unexposed areas of the film to go
  from a milky-white appearance to a transparent
  appearance.

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Preservative of the fixer

• Sodium sulfite
• Prevents decomposition of the fixer
• Makes the fixer able to recycle back into a fixer
  solution

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Hardener or Tanning Agent of the Fixer

• Aluminum chloride, aluminum sulfide, or potassium
  alum.
• Prevents the gelatin of the emulsion from
  swelling excessively.
• Also prevents softening by the wash water or by
  warm air drying.
• Shortens the drying time.

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Acidifier

• Acetic acid
• Accelerates the action of other chemicals
• Neutralize any developer that may be carried over
  from the developer tank.

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Buffer

• Chemical compounds that maintain a constant pH of
  the solution during the fixing process.
• Maintain pH of Fixer
• Should be between 4 and 4.5

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Washing

• Removes the last traces of processing chemicals
  and prevents fading or discoloration.

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Drying

• To dry the radiograph after being processed.
• A blower supplies heated air to the dryer section
  of the film processor which consist of tube like
  rollers. Most of the air is recirculated. The
  rest is vented to prevent buildup of excessive
  humidity in the dryer.

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THE END