Film Processing (Midterms)

• Latent image

  • invisible change that is induced in the silver halide crystal
• Wire mesh

  • used to check for screen-film contact
• Formation of Latent Image

  • photographic effect
• Elements Fixed in a Crystal Lattice

  • Silver
  • Bromine
  • Iodine
• Silver

  • positive ion
• Bromide and Iodide

  • negative ions
• Ion

  • atom that has too many or too few electrons
  • has electric charge
• Latent image center

  • group of silver atoms
• Fewer than 1%

  • interact with the film and contribute to the latent image
• IS

  • device that converts the energy of the x-ray beam into visible light
• Double-emulsion film

  • film has emulsion coating on both sides of the base
• Automatic processor

  • introduced by Pako in 1942
  • could process 120 films per hour with the use of special film hangers
  • 40 minutes - total cycle time for processing one film
• Roller transport system

  • introduced by Eastman Kodak Company in 1956
  • 10 feet long, weighed nearly three quarters of a ton, and sold for approximately $350,000 in today’s dollars
• 90-second rapid processing

  • Eastman Kodak in 1965
  • dry-to-drop time is 90 seconds
  • remains the standard
• Wetting

  • swell the emulsion so subsequent chemical baths can reach all parts of the emulsion uniformly
• Developing

  • latent image is converted to a visible image
• Stop bath

  • film is rinsed in an acid solution designed to stop the developing process and remove excess developer chemicals from the emulsion
• Fixing

  • removes remaining silver halide from emulsion and hardens gelatin
• Washing

  • removes excess chemicals
• Drying

  • removes water and prepares radiograph for viewing
• Developing agents

  • Phenidone
  • Hydroquinone
• Solvent

  • liquid into which various solids and powders can be dissolved
• Water

  • universal solvent
  • solvent for all the chemicals used in processing a radiograph
  • wetting agent; penetrated the gelatin of the emulsion causing it to swell
• Developer

  • change the silver ions of exposed crystals into metallic silver
  • provides electrons to the sensitivity center of the crystal to change the silver ions to silver
• Reduction

  • developer neutralize a positive ion
• Oxidation

  • opposite of reduction
• Development

  • amplifies the latent image
• Hydroquinone

  • principal component of developer
• Secondary constituents of Developer

  • Phenidone
  • Metol
• Synergism

  • two agents working together is greater than the sum of the action of each agent working independently
• Alkali compounds in Developer

  • sodium carbonate
  • sodium hydroxide
• Buffering agents

  • enhance the action of the developing agent by controlling the concentration of hydrogen ions
• Lye

  • strongest alkali; sodium hydroxide
• Restrainers

  • potassium bromide
  • potassium iodide
• Restrainer

  • resist action of the developing agent to only those silver halide crystals that have been irradiated
• Development fog

  • increased fog caused by crystals that have not been exposed are reduced to metallic silver
• Preservative

  • control the oxidation of the developing agent by air
• Aerial oxidation

  • air is introduced into the chemistry when it is mixed, handled, and stored
• Hardener

  • usually glutaraldehyde
  • controls swelling and softening of the emulsion
• Chelates

  • sequestering agents that form stable complexes with these metallic ions and salts