Tanks used for developing sheet film come in a variety of shapes and sizes. They are usually made of stainless steel.

To process sheet film in tanks, load the film into sheet film hangers and then place it into the developing tanks of solutions (fig. 10-5).

FILM WASHING EQUIPMENT

Film washing does not require special equipment. Sheet film can be washed in the same type of tank or tray that is used to process the film or in tanks designed for film washing.

When a tray is used, only one film at a time should be washed. When more than one piece of film is washed at a time, the films will probably rub together and be

Figure 10-5. Film developing tanks.

Figure 10-7. Film washing tank

Figure 10-6. Washing film in trays.

Figure 10-8. Rapid roll-film washer.

scratched. Only line copy types of negatives are usually washed in a tray.

The most effective washing method in a tray is when a siphon device is attached to the edge of the tray. The device siphons water from the bottom of the tray, while fresh water enters at the top (fig. 10-6). Because fixer is heavier than water, it sinks to the bottom of the tray.

The best way to wash hand-processed sheet film (especially more than one sheet at a time) is in a sheet-film washing tank. Film hangers hold individual negatives suspended separately in the tank. Fresh water flows into the bottom of the tank and runs out around the sides at or near the top of the tank (fig. 10-7). When you place the film hangers into the tank, ensure the negatives are separated, so sufficient fresh water reaches all areas of each negative.

WARNING

Aboard ship, hoses attached to potable water spigots can back siphon chemicals or wash water from the trays or sink into the drinking water supply. These hoses must have a backflow preventer installed in the plumbing ^system.

A rapid roll-film washer is excellent for washing hand-processed roll film. It is a cylindrical tank, large enough to hold several spiral reels. The washers come in a variety of sizes that will wash from two 35mm reels to as many as six or eight 120 reels (fig. 10-8).

The rapid roll-film washer is constructed so the wash water enters the tank at the base and flows up

Figure 10-9. Washing film in processing roll-film tank.

through the tank and around the film at a rapid rate. By discharging the water from the top of the tank, you can remove more hypo in a shorter time.

Roll film also can be washed in the roll-film tank in which it was processed. To wash roll film in a roll-film processing tank, simply push a small hose down into the center of the reel and have the faucet turned on, so the water overflows steadily from the tank (fig. 10-9).

TIMERS

Every darkroom should have a reliable timer. Ideally, the timer should have both a minute hand and a sweep second hand. The timer most commonly used in the Navy is a Gray Lab timer (fig. 10-10). Not only does this timer have a minute and sweep second hand but the numbers and hands are fluorescent so they can be seen in the dark A Gray Lab timer also has an alarm (buzzer) that indicates when the time for processing is up.