Stop Bath Solution

T.O. 33B-1-1 6-76 b. Only the amount of replenisher that is consumed in a one-week period SHALL be mixed for use. c. Developing solutions that are not mixed for use or replenishment SHALL be maintained in their closed, original manufacturer's containers. d. Developing solutions SHALL not be used two years past the date of their manufacture. 6.7.7.1.1.1 As was pointed out earlier, all developing agents have a tendency to deposit silver in the unexposed parts of the film emulsion after a certain period of time. This tendency may be retarded or restrained if bromide is added to the solution. However, the addition of the restrainer also tends to slow up development. Therefore, the proportion of bromide in an X-ray developer should be just enough to prevent chemical fog without materially reducing the activity of the solution. It has already been seen that bromide is removed from the film emulsion during development. Therefore, since bromide is a restrainer it is also evident that as each film is developed, restrainer is being added to the solution. In addition, the developing agents gradually lose potency, and as each film is processed the developing time for the next film must be theoretically increased. The most important characteristic of any developing formula is its ability to produce and reproduce a certain degree of film blackening for a particular quantity of absorbed X-ray energy. A consistent end result can be secured only by maintaining constant developer activity. To achieve this stability, the developing solution SHALL be tested and replenished as per process control requirements and manufacturer's instructions. Whenever these two sources of information are in conflict, the process control requirements within this technical order SHALL take precedence. 6.7.8 Stop Bath Solution. WARNING Glacial acetic acid should be handled with adequate ventilation, and great care should be used to avoid injury to the skin or clothing. Always add glacial acetic acid to water slowly, with constant stirring. Never add water to the acid that may cause boiling and splatter strong acid on the hands or face, causing burns. NOTE It is most important that while developer solution is draining off of the radiograph, it SHALL not be allowed to drain back into the developer solution tank. The developer solution that is draining becomes oxidized and reduces the useful life of the working bath. A stop bath solution is used to stop development in the shortest period of time and prevent uneven area of development and subsequent film streaking. The stop bath consists of a mild glacial acetic acid solution designed to neutralize the alkali of the developer. The stop bath also protects the fixing solution, which is slightly acid, from the alkalis of the developer, thereby extending its useful life. The stop bath will become contaminated with developer solution. Much of this contamination can be eliminated by allowing the radiograph to drain for one or two seconds prior to being placed in the stop bath. If sodium carbonate is used to formulate the stop bath it must be used between 65°F (18°C) and 70°F (21°C); otherwise, it will cause carbon dioxide blisters to form in the film's emulsion. Stop bath SHALL be used during hand developing radiographic film, when allowed by the operational environment. 6.7.9 Fixing Solution. After development, the emulsion contains all of the unexposed and undeveloped grains of silver bromide. The undeveloped silver bromide must be removed from the emulsion if the image is to be permanent. To do this a fixing solution or fixer is used. There are only two chemicals in common use that will act as clearing agents by dissolving the undeveloped silver bromide in thin film emulsion. They are sodium thiosulfate (hypo) and ammonium thiosulfate.