c. Thermometer. Since films must be processed at an exact and
predetermined temperature, a thermometer is needed to register the temperature of the
d. Timer. Because of the direct relationship between temperature and time in
processing, the dental specialist must know the exact time any given film is to be left in
each solution. A good watch may be used for this purpose, but it is much better to use
an interval timer. The interval timer is a small clock giving the time in minutes and
fractions of minutes. When set for the exact time required for development, it sounds
an alarm at the expiration of that time.
e. Film Holders. There are three types of film holders (figure 3-2). The frame
type is used for extraoral films and the clip and hinge types are used for intraoral films.
Figure 3-2. Film holders for processing intraoral and extraoral films.
f. Illumination. A photographically safe light must be used to illuminate the
darkroom. The standard for a safelight is that it must be possible to permit
underdeveloped film to be exposed to the light at a distance of 4 feet for 1 minute
without the least evidence of fogging.
g. Sink. A sink is useful in the darkroom for mixing solutions, washing hands,
and disposing of used chemicals. Remember that the fixing solution is not disposed of
like other chemicals. It is retained for silver recovery.
h. Solutions. There are two types of processing solutions. One is used for the
automatic processor and another for the manual processor. They are not designed to
work interchangeably. Before changing the processing solutions, check the
manufacturer's instructions to be sure that you have the proper chemicals for the
processor you are using. Also, follow manufacturer's instruction when preparing them.
Some will require several chemicals mixed with water while others may be used directly
from the container.