3-24. RINSING PROCESS
When the film is removed from the developer, the gelatin emulsion is swollen and
like a sponge, saturated with all the soluble chemicals of the developer solution. Also,
the gelatin contains the black metallic silver image and unexposed, undeveloped silver
bromide crystals. The bulk of the soluble developer chemicals should be removed from
the film before it is placed in the fixing bath and these chemicals replaced by either
fresh or acidified water. Such treatment is necessary to stop the reaction of
development, to neutralize the alkalinity of the residual developer, and to remove the
oxidation products of development. There are two methods of removing these
chemicals--rinsing the film in fresh water and rinsing the film in acidified water.
3-25. WATER RINSE BATH
After development, the film should be rinsed for 30 seconds in circulating fresh
water and drained before being placed in the fixer. This rinse should remove the
soluble developer chemicals form the surface of the film and the pores of the emulsion.
The emulsion on a 14 by 17-inch film holds at least three ounces of developer. To stop
development, the residual developer must be quickly diluted with water. If films are
insufficiently rinsed and repeatedly placed directly in the fixing bath, the chemical
balance of the fixer is eventually upset and its useful life materially shortened. Poor
rinsing causes the acidity of the fixer to be rapidly reduced, the hardening action to be
destroyed, and stains to appear on radiographs. Still, water should not ordinarily be
used for rinsing. An accumulation of developing solution in the rinse bath eventually
oxidizes and when it is carried over to the fixing solution, it streaks and stains
3-26. ACID RINSE BATH
a. Acid rinse baths prolong the life of the fixer and ensure maintenance of the
hardening action. An acid rinse bath eliminates the need for running water (required by
a water rinse bath). The most efficient rinse (stop) bath is one consisting of a dilute
solution of acetic acid in water made according to the following procedure. Add two and
one-half quarts of 28-percent acetic acid to one gallon of water. Stir thoroughly. Add
sufficient water to make five gallons of solution. This bath can be made in a five-gallon
tank and placed between the developer and fixer tanks. The bath immediately stops
development of the emulsion and neutralizes the alkali in the developer contained in the
emulsion.
b. Radiographs should be rinsed in the acid bath for 30 seconds but they may
be left in the bath for as long as one and one-half minutes. Do not overwork the acid
rinse bath. When the activity of the solution is reduced, it will accentuate rather than
prevent stains and streaks. The acid rinse bath will operate satisfactorily within the
normal range of processing temperature when the rapid x-ray developer is used.
During this useful life, the acid rinse bath will rinse about 200 14 by 17-inch films or their
equivalent per five gallons of solution.
MD0954
3-12