Figure 10-9.–Washing film in processing roll-film tank.
through the tank and around the film at a rapid rate. By
discharging the water from the top of the tank, you can
remove more hypo in a shorter time.
Roll film also can be washed in the roll-film tank in
which it was processed. To wash roll film in a roll-film
processing tank, simply push a small hose down into the
center of the reel and have the faucet turned on, so the
water overflows steadily from the tank (fig. 10-9).
TIMERS
Every darkroom should have a reliable timer.
Ideally, the timer should have both a minute hand and a
sweep second hand. The timer most commonly used in
the Navy is a Gray Lab timer (fig. 10-10). Not only does
this timer have a minute and sweep second hand but the
numbers and hands are fluorescent so they can be seen
in the dark A Gray Lab timer also has an alarm (buzzer)
that indicates when the time for processing is up.
PROCESSING METHODS
No matter how many rolls or sheets of film you
develop, it helps when you carry out the processing in
three distinct phases, beginning with preparation. First,
your work area must be clean, and the equipment needed
must be arranged so it is easy to locate in the dark The
second phase is processing. If you are not familiar with
darkroom work, you should complete ALL the
processing steps with dummy or practice film and water
to substitute for processing solutions under white light
and then practice a few times in the dark. The third phase
is film drying.
Figure 10-10.–Gray Lab timer.
302.285
To make the latent image visible and permanent,
you must process the film in different chemical
solutions. There are five steps in the black-and-white
processing phase. The first step is development. In this
step the film is placed in a developer that transforms the
latent image into a visible black metallic silver image.
In the second step the developing solvents are
neutralized, and development is retarded or stopped by
a rinse bath or acid stop bath, respectively. The third step
involves placing the film into a fixing bath to remove
the light sensitive, undeveloped silver halides. The
fourth step is to wash the film to remove all the
chemicals, and the last step is to dry the film. Each of
these steps is explained further in this chapter, since
there are certain controls that must be applied to each
step.
Some of the processing steps may be carried out in
white light, while others must be done under appropriate
safelight conditions or in total darkness. The steps that
must be done in darkness or under suitable safelight
conditions begin when the film package, holder, or roll
is opened and end when the film is removed from the
fixer.
As discussed earlier, there are five steps in film
processing. The steps and the lighting conditions under
which they are carried out are as follows:
1. Development-dark or appropriate safelight
2. Rinse or stop bath-dark or appropriate safelight
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