weather because the water-laden gelatin emulsion may soften and distort the
radiographic image. Under these conditions, it is safest to use only the dryer fan.
Overheating of the dryer should be avoided because very rapid drying is apt to cause
distortion of the radiograph.
e. Drying Rack. When a small number of films are to be dried each day and a
cabinet dryer is not available, film hangers may be inserted in a wall drying rack. The
rack may be simply a board in which holes have been drilled into which one end of the
hanger crossbar can be inserted while the film is drying.
3-38. DRYING TIME
The time required to dry a film is dependent upon the efficiency of the hardener
in the fixing solution, the amount of water retained in the gelatin emulsion after washing,
the velocity and temperature of the drying absorption is reduced to a minimum by the
use of a reasonably fresh fixing solution which will assure proper hardening of the
emulsion. Ideally, the humidity should be below 50 percent and the temperature under
90F. When films are dried in cabinet dryers, they should be adjusted so that drying
takes place in 10 to 20 minutes. The use of infrared lamps is not recommended, since
they cause unequal drying of the film surfaces.
3-39. PREPARING THE RADIOGRAPH FOR FILING
After the radiograph has been dried, the sharp and/or punctured corners caused
by the hanger clips should be trimmed with a corner cutter or scissors. This enhances
the appearance of the radiograph, facilitates its insertion into an envelope, and
precludes its scratching other radiographs with which it may come in contact. After its
corners are trimmed, the radiograph should be placed in a heavy manila envelope of
proper size and all essential identification written legibly in the space provided on the
face of the envelope. Given to the radiologist in this condition, it is ready for subsequent
Section III. FACTORS AFFECTING FILM PROCESSING
3-40. MECHANICS OF SILVER DEPOSITION
a. With the exposed emulsion considered as a whole rather than as its
constituent silver bromide crystals, the various stages of development are illustrated in
figure 3-1. Assume that an aluminum step wedge (A) is exposed using an x-ray film (B)
as the recording medium. If the film is represented in enlarged cross-section, upon
exposure, (C) a latent image of the object is produced in the silver bromide emulsion.
The latent image is represented by the dotted area, and it consists of representations of
the six portions of the wedge. The radiation reaching the film is of varying intensity after
its passage through the wedge and the relative absorption of each step of the wedge is
represented. The radiation passing through step number one of the wedge (A) is only
partially absorbed; hence, more silver bromide is exposed than on that portion of the