X Ray Film Processing-
Radiographic Film processing is the procedure that transforms the latent picture (invisible) on the film into a visible image through a number of processes. Industrial radiography X-ray films are made up of an emulsion layer and a blue-tinted polyester base layer. On both sides of the base, the emulsion is covered in layers and shielded by thin outer protective layers. Gelatin, additives, and silver halides serve as the photosensitive components of the emulsion. When affected by X-rays, gamma rays, secondary electrons, visible light, or fluorescent light, the silver halides produce a picture.
Types-
- Manual X Ray Processing
- Semi-automatic
- Fully automatic.
a. without replenisher
b. with replenisher.
Manual X ray Film Processing-
After an X-ray film has been exposed, it must be developed to create a permanent visible radiographic picture that can be preserved for a period of years without degradation. The latent picture is converted into a visible image by processing. The term “processing” refers to the several steps that collectively result in the visible, permanent picture and includes steps for developing, rinsing, fixing, washing, and drying.
For manual processing a floating thermometer, a timer and the time -temperature chart are essential.
Exposure of film / Latent image formation-
The ionisation of the exposed silver bromide crystals in the emulsion layer prior to processing happens when photon energy from the patient emerges, resulting in the latent (invisible) picture generation. Electrons are knocked out as a result of the Compton and photoelectric interactions, which are the main interactions with the bromide crystals. As a result, when the radiograph is exposed, something physical happens. Minuscule quantities of silver ions are generated on the surface of the silver bromide crystals in the emulsion when X-ray photons [or light photons] impact them, and bromine is released and absorbed by the gelatin.With the addition of silver iodide, crystals are also intentionally built with electron traps (sensitivity specks) made of sulphur impurities. The sulphur in the sensitivity specks traps electrons, giving it a negative charge. A latent picture is formed in the film emulsion when this condition is created.
AgBr + X-ray photons = Ag + + Br –
No physical test has yet been developed that can view or identify the deposits of free (ionised) silver ions that make up the latent picture. It stays in the X-ray film’s emulsion until chemical processing steps convert it into a visible silver picture. The free electrons travel through the crystal until they are drawn to a sensitivity site, where they are trapped and give the site a negative charge.
Standard Time & Temperature Chart (Manual Processing)
Maintaining the correct time and temperature parameters is essential for achieving optimal radiographic contrast and preventing emulsion damage:
| Processing Step | Standard Time (at 20°C / 68°F) | Key Action & Darkroom Note |
| Rinse / Stop Bath | 30 – 45 seconds | Continuous agitation in a running water or dilute acetic acid bath to halt development immediately. |
| Fixing | 5 – 10 minutes | Rule of Thumb: Total fixing time is approximately twice the clearing time. |
| Final Washing | 15 – 20 minutes | Running water bath to thoroughly remove residual hypo and soluble silver thiosulfate complexes. |
| Drying | 20 – 30 minutes | Warm, dust-free drying cabinet (air temperature should not exceed 45°C–50°C). |
Steps Of Processing-
1. Development – Converts latent image to black metallic silver.
3. Wash [stop bath] – Removes excess developer.
4. Fixing and Hardening – Dissolves out unexposed silver halide crystals.
5. Washing – Removes products of processing.
6. Dry – Removes water
Development-
Since exposed radiographs with a latent image are more sensitive to energy, processing should be done as quickly as possible. Film packages should only be opened in a dark room or in a space with safe lighting.
The maker of the chemical often specifies the development time. Keep in mind that the length of time for developing depends on the developer temperature. Visual examination is favoured over time-temperature developing when employing the manual processing method. Sight developing is the term for this manual examination, which entails adjusting the time in accordance with a visual assessment of the film density while the film is still in the tank. This method calls for focus, competence, and is frequently prone to mistakes. If at all possible, try to avoid sight developing.
Developmental agents, accelerators, preservatives, restrainers, hardeners, and a solvent make up the developer.
1.Developing agents–
Hydroquinone is the developer’s major active component. It causes fully exposed silver crystals to become black. It can turn exposed grains of silver halide into black metallic silver. The unexposed silver halide crystals are little or not at all affected by the developing agent.
2.Accelerators
Chemicals known as accelerators boost the developer’s activity. To raise the pH to an alkaline range of 9.8 to 11.4, substances like potassium carbonate or sodium carbonate are utilised. The swelling and softening of the emulsion brought on by this rise in pH makes the developing agent more efficient.
3.Preservatives.
To make the developer solution last longer, a preservative (sodium sulphide or cycon) is added to hydroquinone (it takes longer to oxidize).Preservatives stop the quick oxidation that alkaline development agents can cause. Additionally, they aid in preserving a steady pace of growth and avoid emulsion layer stains.
4.Restrainers
Restrainers restrict the developing agent’s activity to the film’s exposed silver bromide crystals. The hydroquinone’s action is constrained to the exposed silver crystals by another chemical used in the development process. This purpose is served by potassium bromide, also known as a restrainer. Because they forbid, restrainers are also known as antifoggant agents.
5. Hardeners
The amount of emulsion that can swell requires the addition of a hardener since the film expands throughout the developing process. In automated processors, hardeners are frequently introduced to developers. They prevent the emulsion from too expanding and harden the film during processing. The rollers in the automated processor might hurt the gelatin emulsion if it swelled much. Glutaraldehyde is the substance that is most frequently utilised for this purpose. The automated film processor’s rollers might harm the emulsion if it swells excessively, destroying the x-ray.
6. solvent
In the developer solution, water serves as a solvent. Solvents aid in the swelling of the film’s emulsion layer, allowing developing solutions to reach all of the embedded silver crystals.
Common Processing Artifacts & Troubleshooting
Improper rinsing, fixing, or drying techniques cause distinct film defects:
Dichroic Fog (Pinkish/Greenish Tint): Caused by inadequate rinsing or stop bath, leading to alkaline developer carry-over into the acidic fixer tank.
Yellow-Brown Staining (Hypo Retention): Results from incomplete final washing or using exhausted fixer solution, leaving residual thiosulfate that degrades into silver sulfide over time.
Water Marks / Droplet Artifacts: Caused by localized uneven drying due to failing to shake off excess water or skipping a wetting agent bath before drying.
Milky or Cloudy Film: Occurs when the fixer solution is exhausted or the clearing time is insufficient, leaving unexposed silver halide crystals in the emulsion.
Brittle Emulsion / Reticulation: Caused by severe temperature differences between the processing chemical tanks and the wash water, producing a puckered or cracked network pattern on the emulsion.
