Film Processing Flashcards
Film Processing
Converts latent image to manifest image Two basic methods used: Manual and Automatic
Manual Processing Steps
Wetting Agent – (optional) Developer – most important processing step Stop Bath or Water Rinse Fixer Washing – prevents hyporetention Drying
Processing Chemistry Developer
Most important processing step Converts latent image to manifest image Uses oxidation/reduction reaction or redox
Developer Chemicals
Component: Developing agents, Buffer, Restrainer, Preservative, Hardener, Sequestering agent, Solvent
Accelerator, Activator, or Buffering Agents
- Maintain alkaline (high-pH) medium - Soften and swell film emulsion - Chemicals used can be either sodium carbonate, sodium hydroxide, potassium carbonate, or potassium hydroxide
Restrainer, Regulator, Antifoggant, or Starter
- Restrains the action of developing agents to help prevent chemical fog - Chemicals used can be either potassium bromide or potassium iodide
Hardener
- Keeps the film emulsion from sticking to rollers in processor - Weaker hardener than is found in fixer solution - Chemical agent is glutaraldehyde
Solvent
- Other components are mixed with solvent to create developer solution - Agent used is water (should be drinkable in quality)
Sequestering Agent
- Used for developer solutions that are mixed from concentrate - Keeps impurities found in tap water from oxidizing reducing agents - Chemical agent is ethylenediamine tetraacetic acid (EDTA)
Developer Solution Options
- Ready or Pre-mix – easier but more expensive - Concentrate – cheaper but less convenient - Three-part kit is mixed with water - Must be mixed properly
Processing Chemistry Fixer
- Removes unexposed and undeveloped silver halide crystals - Stops development process - Permanently hardens film emulsion for archival storage
Fixer Components: Fixing agent, Clearing agent
Removes unexposed and undeveloped silver halide crystals (film clearing)
Preservative
- Helps recycle fixing agent - Chemical agent is sodium sulfite - Level should be maintained in range of 15 to 50 g/L
Hardener or Tanning Agent
- Permanently hardens film emulsion for long-term archival storage - Hardening process is also called tanning - Chemical agents can be potassium alum, chrome alum, or aluminum chloride
Acidifier, Activator, or Buffer
- Neutralizes any developer remaining in film emulsion - Maintains acid (low-pH) medium for fixing agent - Chemical agent can be either acetic or sulfuric acid
Sequestering Agent
Helps prevent development of aluminum hydroxide (alkaline compound)
Solvent
- Other components are mixed with solvent to create fixer solution - Agent used is water (should be drinkable in quality) - Specific gravity should be between 1.077 and 1.11 to ensure proper concentration
Fixer Solution Options
- Ready or Pre-mix – easier but more expensive - Concentrate – cheaper but less convenient - Two-part kit is mixed with water - Must be mixed properly
Washing Step
- Removes excessive fixer to prevent hyporetention - Hyporetention can cause white, powdery residue (short term) and brown stain (long term) - Hyporetention degrades archival quality of film images
Developer Activity Factors
- Solution Temperature - Immersion Time - Solution Concentration - Type of Chemicals - Solution pH - Exhaustion/Replenishment
Processing Time
- Developer immersion time should be maintained to within ± 2% to 3% of manufacturer’s specification - Can be checked with time-in-solution test tool and a stopwatch
Replenishment Rate
- Values indicated on flow meters should be within ± 5% of manufacturer’s specification - If no flow meters are present, can be checked by catching solution in graduated cylinder and measured
Developer or Reducing Agents
- Phenidone – fast acting, producing optical densities under 1.2 - Hydroquinone – slow acting, producing optical densities above 1.2 - Uses Synergism or Superadditivity
Solution temperature
- Developer temperature should not vary by more than ± 0.5° F (0.3° C) from manufacturer’s specification - Fixer temperature should be maintained within ± 5° F (3° C) of developer temperature - Wash water should be either the same or about 5 degrees colder than fixer temperature
Solution pH
- Developer pH should be maintained between 10 and 11.5 - Fixer pH should be maintained between 4 and 4.5 - Can be checked by using either test paper or a pH meter
Specific Gravity and Proper Mixing
- Developer should be maintained between 1.07 and 1.1 - Fixer should be maintained between 1.077 and 1.11 - Can be checked with a hydrometer