Processing of films
Definition of processing
Processing theory
Diagram
Practical processing methods
Manual
Automatic
Self-developing films
Requirements for manual processing
Absolute 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 cycle
The 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 functions
Phenidone- 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
Fixer’s constituents and their functions
Ammonium thiosulphate- removes
unsensitized crystals
Sodium sulphite- preservative
Aluminium chloride- hardener
Acidic acid- maintains pH
Water- 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 processing
Processing 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
Advantages
Time saving
No need for a darkroom
Standardized processing conditions
Disadvantages
Strict 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 films
Advantages
- No darkroom or processing facilities
are needed
- Time saving- the final radiograph is
ready in about a minute
Disadvantages
Poor overall image quality
The 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