No matter how many rolls or sheets of film you develop, it helps when you carry out the processing in three distinct phases, beginning with preparation. First, your work area must be clean, and the equipment needed must be arranged so it is easy to locate in the dark The second phase is processing. If you are not familiar with darkroom work, you should complete ALL the processing steps with dummy or practice film and water to substitute for processing solutions under white light and then practice a few times in the dark. The third phase is film drying.

Figure 10-10. Gray Lab timer.

To make the latent image visible and permanent, you must process the film in different chemical solutions. There are five steps in the black-and-white processing phase. The first step is development. In this step the film is placed in a developer that transforms the latent image into a visible black metallic silver image. In the second step the developing solvents are neutralized, and development is retarded or stopped by a rinse bath or acid stop bath, respectively. The third step involves placing the film into a fixing bath to remove the light sensitive, undeveloped silver halides. The fourth step is to wash the film to remove all the chemicals, and the last step is to dry the film. Each of these steps is explained further in this chapter, since there are certain controls that must be applied to each step.

Some of the processing steps may be carried out in white light, while others must be done under appropriate safelight conditions or in total darkness. The steps that must be done in darkness or under suitable safelight conditions begin when the film package, holder, or roll is opened and end when the film is removed from the fixer.

As discussed earlier, there are five steps in film processing. The steps and the lighting conditions under which they are carried out are as follows:

1. Development-dark or appropriate safelight

2. Rinse or stop bath-dark or appropriate safelight

3. Fix-dark or appropriate safelight

4. Wash-white light

5. Dry-white light

In addition to exposure, there are four factors in development that control image density, contrast, and, to a limited degree, the uniformity of individual densities in a negative. These four factors are the type of developer used, development time, temperature of the developer, and agitation as follows:

Type of developer. One type of developer cannot cover all film exposure/processing situations. For example, film exposed under poor lighting conditions may require a vigorous developer to bring out as much image detail as possible, while film exposed under normal conditions requires a normal working developer. There are many different developers, each provides a different activity and quality of development. The actual choice of the developer to use depends on the following: the type of film, conditions under which it was exposed, type of negative required, developing time that is best for the method of development to be used, and the manufacturer's recommendation.

Time and temperature. Many factors must be considered if you want to ensure correct development during film processing. Two of these factors are the length of time the film is allowed to develop and the temperature of the developer solution. Both factors can have a significant impact on the quality of the processed film.

As explained earlier, the activity of a developer increases as its temperature increases. Film development carried out for a given time at a given temperature produces both predictable and desired results-assuming, of course, that the film has been exposed properly. When film is developed for a given time at a given temperature, it is called "time and temperature development."

In the time and temperature method of film processing, as in any method of film processing, if the film is developed for too short a time or at too low a temperature, a weak, low-contrast image results. Underdevelopment can result in insufficient highlight density. On the other hand, if the negative is developed for too long a period or at too high a temperature, the result is a negative having too much density. The developer solution overdevelops the exposed areas and may even develop some of the unexposed silver halides.

For correct development, both time and temperature must be accurately controlled. Within limits, time can

be adjusted for a given temperature, or temperature can be adjusted for a given time.

There is a definite correlation between time and temperature. When it is impossible to maintain solution temperature at the desired level, time can be shortened or lengthened to compensate. As the temperature increases, developing time must be decreased to provide equivalent development. As the temperature decreases, development time must be increased.

The normal temperature for hand processing most black-and -white film is 68F (T-Max film with T-Max developer is 75F). There are several reasons for this standardization. At a temperature of 68F, the gelatin swells sufficiently to allow adequate penetration of the developing solution without oversoftening to the point where it is easily damaged (which occurs at higher temperatures). Temperatures lower than 68F slow development excessively. Only when time is of the utmost importance are accelerated temperatures used. In most instances when high temperatures are used, the film is treated in a hardening bath before processing, or the film is designed specifically for being processed at such temperatures. Since a rise of several degrees in temperature shortens development only a small amount, there is little to be gained by deviating from standard processing temperatures.

When you know the time and temperature relationship for a given film and developer combination, processing in total darkness becomes simple. You simply adjust solutions to the prescribed temperature and then process the film for the required time. Assuming proper exposure, time and temperature processing can produce a correctly developed negative without your having to see what is happening in the solution.

All solution temperatures (developer, rinse, fix, and wash) should be as close to each other as possible. When there is considerable difference in the temperature of the solutions, excessive graininess may result, or the emulsion may be subject to excessive expansion and contraction that causes it to wrinkle or crack This effect is called reticulation. Since reticulation is not correct-able, it causes the negative to be useless for printing.

The temperature of solutions may be adjusted by surrounding them with hot water, cold water, or ice. Never add water or ice directly to a solution because it dilutes the developer to an unknown degree. Ice may be placed in a container and suspended in the solution. An immersion heater may be used in the solution to raise its temperature.

Agitation. If a film is placed in a developer and allowed to develop without movement, the chemical action soon slows down because the developing agent in contact with the surface of the emulsion becomes exhausted and bromide (a restrainer) is released as a by-product. When the film is agitated, however, fresh solution is continually brought to the surfaces of the film, and the rate of development remains constant. Therefore, agitation also has an important effect on the degree of development. An even more important effect of agitation is it prevents uneven development. If there is no agitation, the exhausted solution that became saturated with bromide from the emulsion may flow slowly across the film from the dense highlight areas and produce streaks. Constant agitation is usually recommended for the first 30 seconds of tank development and for the entire developing time when the film is being processed in a tray. After the initial 30-second agitation cycle, the film should be agitated for 5 seconds, once every minute during the remaining time.

The time, temperature, and amount of agitation required for a film/developer combination are recommended by each manufacturer of film or developer. These recommendations are in the instructions that accompany the film or developer. Another reference source is the Photo-Lab-Index.

There are three different methods of processing film by hand. These are as follows: the tray, the sheet-film tank, and the roll-film tank. Each method is discussed here with an example of the darkroom arrangement used.