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:

• Artifacts
• Surface quality
• Image tone
• Stability
• Film drying

There are three main stages in film processing

1. The exposed film is first treated with the developer to bring out the image.
2. Fixer is then used to hold that image in place.
3. 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

1. Developing Agents
2. Buffering Agents
3. Preservatives
4. Restrainers
5. 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