3-56. DILUTION OF DEVELOPER
The solution is often improperly mixed because of a disregard for the
manufacturer's instructions. Poor radiographic quality may result from using solutions,
which do not have the required strength. Sometimes this happens because processing
tanks have a greater capacity than is supposed. Many so-called "five-gallon" tanks
actually have a capacity of six or more gallons. Hence, although the time-temperature
method of development is strictly adhered to, the radiographs receive 20 to 25 percent
less than normal development because of developer dilution. Always ascertain the
exact capacity of the tanks to a level one-inch below the top of the tanks. Dilution of the
developer also occurs when water is used to maintain the required level of the solution.
If the developer is low, always restore the correct level by adding fresh solution.
3-57. EXHAUSTION OF THE DEVELOPER
The exhaustion of the developer is affected by the rate of oxidation (through
contact with the air or by use), the number of films processed and their average density,
contaminating substances, and accumulation of by-products of the development
reactions as well as secondary changes in the developer (of mechanical or chemical
origin such as the formation of sludge or the accumulation of insoluble matter). The
manner in which exhaustion of the developer occurs is illustrated in the chemical
reaction described earlier in this subcourse. Development of the silver bromide
emulsion oxidizes the developing agent; releases acid hydrogen ions (which reduce the
alkalinity of the solution) and liberate bromine ions (which accumulate in the solution
and inhibit its activity). All of these changes lower the activity of the developer. To
maintain a developer solution with good working properties, use the replenisher system.
3-58. AGITATION OF THE SOLUTION
a. To assure uniform activity over the entire surface of the x-ray film during
processing, it is necessary after a period of activity to stir the developer and fixer
solutions thoroughly, using different paddles. Stirring is particularly important in the
case of the developer. When the developer solution is not stirred in the tank, there is a
tendency for the lower areas of the film to receive less development than the upper
areas because the temperature of the solution is usually lower at the bottom of the tank
than it is at the top. Also, the reaction products of development that tend to restrain
development are heavy and settle to the bottom of the tank. The lower temperature and
higher concentration of reaction products at the bottom of the tank cause unequal
development of the film.
b. Some agitation of the developer should be made by moving the hanger up
and down several times during the development period because as development takes
place, reaction products diffuse out of the emulsion and film downward over the film
surface, affecting the development of film areas over which they pass. Some agitation
serves to disperse the reaction products throughout the solution as they emerge from
the emulsion and thus to prevent local development abnormalities.