Processing of films Definition of processingProcessing theoryDiagram

Practical processing methodsManual

Automatic

Self-developing films

Requirements for manual processingAbsolute light-tightness of the dark room

Adequate working space

Adequate ventilation

Adequate film storage facilities

Safelights

Processing equipments-tanks,

thermometers immersion, heater,

timer, film hangers

Adequate washing facilities

Manual processing cycleThe exposed film packet is unwrapped and the film clipped on to a hanger

The film is immersed in developer (at 20 degrees for 5 minutes) and agitated several times

Rinse the residual developer for 10 seconds

• Immerse the film in the fixer for 8- 10 minutes

• Wash the film under running water for 10- 20 min. to remove the residual fixer

•The film is dried in a dust – free atmosphere

Constituents of developer solutions and their functionsPhenidone- bring out the image

Hydroquinone- builds contrast

Sodium sulphite- reduces oxidation

Potassium carbonate- activates developing agents

•Benzotriazol- prevents fog

•Glutaraldehyde- hardens the emulsion

•Fungicide- prevents bacterial growth• •Buffer- maintains pH ( 7+)

•Water- solvent

Important points regarding development

The alkaline developer should be made up according to manufacturer’s instruction

Solutions should be changed every 10-14 days, irrespective of the number of films processed during that time

The recommended time is 5 minutes at 20 degrees

Fixer’s constituents and their functions

Ammonium thiosulphate- removes unsensitized crystals

Sodium sulphite- preservativeAluminium chloride- hardenerAcidic acid- maintains pHWater- solvent

Important notes regarding

fixing

Avoid contamination with developer and prepare according to manufacturer’s recommendations

Films should be fixed for double the clearing time (the time it takes to remove the unsensitized silver halide crystals)

•Films may be removed from the fixer after 2-4 minutes for wet reading but should be returned to the fixer to complete fixing

•Inadequate fixed films may appear greenish, yellow or milky and later brown

Automatic processingProcessing cycle- it is the same as for manual processing except that the rollers

squeeze off any excess developing solution before passing the film on to the fixer

Infection control measures

AdvantagesTime saving

No need for a darkroom

Standardized processing conditions

DisadvantagesStrict maintenance and regular cleaning are essential

Some models need to be plumbed in

Equipment is relatively expensive Smaller machine cannot process large extraoral films

Self-developing filmsAdvantages

- No darkroom or processing facilities are needed

- Time saving- the final radiograph is ready in about a minute

DisadvantagesPoor overall image qualityThe image deteriorates rapidly with time

There is no lead foil inside the film packet

The flexible film packet is difficult to use in positioning holders

Relatively expensive