Conventional Film Developing Stages
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Below is the stages that conventional film undergoes for wet processing. The process can either be performed by hand or with an automatic processor. Processing chemistry plays a key role in image formation and also affects other image characteristics such as:
There are three main stages in film processing
When broken down the chemical developer contains:
Wetter - For chemicals to penetrate through the gelatin emulsion on the film the radiograph must be treated with a wetting agent
Phenidone - Produces grey shades rapidly on the radiograph
Hydroquinone - Produces black shades on the radiograph slowly
Accelerator - Oxygenates the solution to speed up the development process (too much creates a graining appearance on the radiograph)
Buffer Agent - Helps to swell the emulsion, controls the PH, produces alkalinity
Restrainer - An anti fog agent stops unexposed crystals from being developed
Hardener - Frequently used in automatic processors to controls emulsion swelling and help protect the
film from processor artifacts
Sequestering Agent - Counters the adverse effects of metallic impurities, calcium and iron and stabilises the developing agent.
Fixing Agent - Amonium thiosulphate removes undeveloped Silver (Ag) Halide from emulsion
Hardener - Stiffens, shrinks and hardens the film emulsion therefore protecting the film from damageas well as accelerating film drying time
Preservative - Sodium Sulphite maintains the chemical balance and improves the shelf life of the product
Buffer - Acetate maintains the correct PH
Sequestering Agent - Removes aluminium ions
Solvent - H2O dissolves other compounds
- Artifacts
- Surface quality
- Image tone
- Stability
- Film drying
There are three main stages in film processing
- The exposed film is first treated with the developer to bring out the image.
- Fixer is then used to hold that image in place.
- The film undergoes a drying process.
Developer
Developer produces the visible image. Its activity is affected by pH changes, oxidation, evaporation, temperature and processing byproducts (bromide). Proper replenishment of the developer mitigates these effects.The five parts of the developer solution are- Developing Agents
- Buffering Agents
- Preservatives
- Restrainers
- Hardeners
When broken down the chemical developer contains:
- Wetter
- Phenidone
- Hydroquinone
- Accelerator
- Buffer Agent
- Restrainer
- Hardener
- Sequestering Agent
- Preservatives
- Fungicide
- Anti frothant
Fixer
Once developed the fixer holds the image in place.The chemical fixer contains:- Fixing Agent
- Hardener
- Preservative
- Buffer
- Sequestering Agent
- Solvent
Drying
- With warm dry air
Developer in Detail
Wetter - For chemicals to penetrate through the gelatin emulsion on the film the radiograph must be treated with a wetting agent
Phenidone - Produces grey shades rapidly on the radiograph
Hydroquinone - Produces black shades on the radiograph slowly
Accelerator - Oxygenates the solution to speed up the development process (too much creates a graining appearance on the radiograph)
Buffer Agent - Helps to swell the emulsion, controls the PH, produces alkalinity
Restrainer - An anti fog agent stops unexposed crystals from being developed
Hardener - Frequently used in automatic processors to controls emulsion swelling and help protect the
film from processor artifacts
Sequestering Agent - Counters the adverse effects of metallic impurities, calcium and iron and stabilises the developing agent.
Fixer in Detail
Fixing Agent - Amonium thiosulphate removes undeveloped Silver (Ag) Halide from emulsion
Hardener - Stiffens, shrinks and hardens the film emulsion therefore protecting the film from damageas well as accelerating film drying time
Preservative - Sodium Sulphite maintains the chemical balance and improves the shelf life of the product
Buffer - Acetate maintains the correct PH
Sequestering Agent - Removes aluminium ions
Solvent - H2O dissolves other compounds