3-51. LOW TEMPERATURES
Temperatures below 60F inhibit the activity of one of the reducing agents. If the
x-ray specialist is not certain of the temperature, the appearance of the film may lead
him to believe that insufficient exposure has been given. Hence, the exposure time is
usually increased in a futile effort to increase radiographic density and a cycle of
overexposure and underdevelopment occurs, resulting in poor radiographic quality. If
solutions gradually warm up to a more normal temperature and the fact are not
observed, the sequel is that no compensating reduction in exposure time is made. Over
development of an overexposed film ensures and results in deposits of excessive
density on the radiograph. Know the correct temperature at all times so that optimum
developing times and correct exposures can be used.
3-52. HIGH TEMPERATURES
A developer at 80F requires less time to produce a satisfactory image, but the
density of the image is likely to be excessive. This high temperature will cause rapid
oxidation of the solution, which will then produce an underdeveloped, fogged
radiograph. Besides all this, the emulsion may melt from the film unless the solutions
are specially treated. When development must take place with temperatures of 75F
and above, the special procedures described later in this subcourse must be used.
Developer begins to age as soon as it is mixed and is fresh only while the active
chemicals are still in approximately the same concentrations as when the solution was
originally mixed. Each film developed not only removes solution by absorption and
surface cohesion, but also weakens the developer in the tank. The developer solution
should never be used after three months, because a weakened solution will produce
weak images and may cause chemical stain or fog. During development, chemical
reactions take place, which exhaust the solution. The developing agents are destroyed
by their action in reducing the exposed silver bromide crystals in the emulsion to and
bromide, as well as oxidation products, slow up the speed of development. Other
factors that shorten the usefulness of the developer are high temperatures, dilution with
3-54. DATE OF DEVELOPMENT
The rate of development is affected by the chemical activity of the developer.
This activity is determined by the type and quantity of the ingredients used for the
solution, the dilution of the solution, the degree of its exhaustion, and the temperature.
The nature and concentration of the reducing agents and the effective alkalinity
of the solution affect the composition of the developer.