Processing
Professor, Nancy Rivaldo
Monroe Community College
Introduction
Compounds of silver & halogens
are sensitive to x-radiation
Film consists of a base covered
with emulsion of silver halide
crystals embedded in gelatin
Gelatin keeps crystals evenly
suspended over the base
Cont.
Gelatin swells in water exposing
the silver halide crystals to the
chemicals in the developing
solution
Gelatin shrinks as it dries leaving a
smooth surface that becomes the
radiograph
Selective Reduction
During processing a selective
reduction of exposed silver halide
crystals takes place which means
nonmetallic elements, the halides,
are removed and only the exposed
(metallic) silver remains
What Happens?
Film exposed to x-radiation
Energy of photon absorbed by
silver halide crystals in emulsion
(photoelectric interaction)
An image is captured
Image not visible (latent)
Cont.
Image made visible through
processing
Film placed in developer
Exposed halide (nonmetallic) is
removed from the silver
Silver turns black and remains
Silver halide crystals that have been
ionized changed into black grains
Cont.
Black metallic silver remaining forms
the image and the exposed area of
the emulsion is visible
Image is made up of grains of black
metallic silver
Crystals that have not been ionized
will remain in crystal form and not
changed during developing stage
Cont.
Amount of silver deposited will vary
with thickness of tissue penetrated
--soft tissue = black = radiolucent
--dense tissue = white where rays
blocked = radiopaque
Time Temperature
Technique
The basis for this is that the optimum
amount of precipitation of silver for
the amount of x-ray energy
delivered to the object takes place
in a specified amount of time with
the developing solution at a certain
temperature. (Therefore, if films
are left in the developer too long
more silver precipitates then was
intended)
Developer Chemicals
1. Developing or Reducing Agent
2. Alkalizer, accelerator or activator
3. Preservative
4. Restrainer
Reducing Agent
Hydroquinone--works slowly but
steadily to build density and
contrast
Elon--produces detail slowly
Function of reducing agent is to
change exposed crystals to black
metallic silver
Alkalizer
Sodium carbonate
2 functions:
--softens & swells emulsion gelatin
to allow reducing agent to reach
the crystals
--provides required alkaline
medium for reducer to work
Preservative
Sodium sulfite
Antioxidant
Restrainer
Potassium bromide
Controls action of developing
agent
Prevents chemical fog
Fixer Chemicals
Clearing or fixing agent
Acidifier
Preservative
Hardener
Clearing Agent
Sodium or ammonium thiosulfate
Removes unexposed or
undeveloped crystals from
emulsion
Acidifier
Acetic acid
2 functions:
--provides required acidity for fixing
agent to work
--provides acid medium to
neutralize alkali of developer and
stops action of developer
Preservative
Sodium sulfite
Prevents oxidation
Hardener
Potassium aluminum
Shrinks and hardens the gelatin
Wetting Agent
Used in developer to hasten film
developing
Reduces surface tension of film
If a properly washed film is
immersed for 1 minute in water to
which wetting agent has been
added the film will dry faster
Cutting Reducer
Farmer’s Solution
Used in an emergency to lighten
films
Will even lighten film exposed to
white light
Manual Processing
Steps
Develop for 5 minutes at 68
degrees Fahrenheit (place film in
developing solution using an
agitating motion)
Using an agitating motion rinse film
for 20 to 30 seconds
Fix for 4 minutes
Wash for 10 minutes in running
water
Dry film thoroughly
Automatic Processing
Uses mechanical transport
systems
Uses higher temperatures
Phenidone replaces elon for gray
tone production
Hardening agent (gluteraldehyde)
and antiswelling agent (sulfide)
added to developer to prevent
emulsion from sticking to rollers
Cont.
Hardening agent also added to
fixer to prevent sticking
Sequence is developer, fixer, rinse
and dry