(4) To sight develop a film, you may place a finger behind the densest part
of the film and then view it against a safelight. If the shadow of the finger cannot be
seen through the film, development should be terminated. To avoid causing aerial fog,
the x-ray specialist should be particularly careful not to keep the film out of the
developing solution for too long a time.
b. Solutions of Unknown Temperature and Strength.
(1) It is not advisable to process films by the sight method if the temperature
and/or the strength of solutions are unknown. For consistency in film quality,
standardized processing times must be established for both the developer and the fixer.
This may be done by using the following methods.
(2) A simple test for proper development time can be carried out within a
few minutes. Using an eight by 10-inch, cassette, flash-expose half the film to x-rays
while covering the other half with lead. Then, in the darkroom, cut the exposed film into
strips so that each strip has one exposed and one unexposed end. Only one strip is
used in making the test, so the remainder of them should be stored in a lightproof
container. Using a stopwatch with a second hand, place the strip of film in the
developer so that it can be easily observed by the safelight illumination. The instant that
the exposed half of the film becomes different in appearance from the unexposed half,
note the time elapsed in seconds. Then, divide the number of seconds elapsed by 10;
the result gives a suitable development time in minutes. For example, if it took 35
seconds for a density to appear on the exposed half of the film, then the proper
development time for that solution at that temperature would be 35 divided by 10,
or 3-1/2 minutes.
(3) To estimate the proper fixing time, place a film in the fixer (the first film
processed will do satisfactorily) and note the time it takes for the film to clear. Triple this
time for the complete fixing of all films. For example, if it took six minutes to clear a film,
then all films left in the fixer for 18 minutes would be satisfactorily hardened.