hands, a photographer can process as many as 10 sheets of film at one time. Some metal multi-sheet film frames are available for handling multiple sheets as one; they require larger trays than the stacking methods, and generally preclude any stacking for risk of film damage. The drawbacks of tray processing are that the photographer must spend the entirety of the processing time in the dark, with their hands in the various chemicals (some wear gloves, but they can reduce the ability to feel the individual sheets of film). Some photographers also have problems with scratching of the film's emulsion when using this method. Tank processing Tank processing is also referred to as "deep tank" processing or "dip and dunk" processing. The equipment requirements are greater than for tray processing; a tank for each processing solution is required, along with film hangers for each sheet of film the photographer wishes to process. A film hanger is a metal frame with perforated edges which holds a single sheet or multiple sheets (usually four) of film. The films are inserted into the film hangers, and then submerged into the tank. Agitation is performed by lifting the hangers out of the tank, tilting them to one side to allow them to drain for a brief moment, resubmerging them, lifting and tilting to the other side, and resubmerging. Many photographers will bang or tap the hangers on the tank's top after the second tilt, to dislodge any air bubbles that have stuck to the film. Tanks are also helpful for long development techniques such as "stand" development. Stand development is very individualized, and every practitioner has his or her own routine, but in general, after an initial agitation in the developer, film is simply allowed to stand motionless in (generally highly dilute) developer, with no agitation, for very long intervals, up to hours. Large tank processing has higher equipment requirements, and a larger volume of solution is required for each step. A tank for film can require 2 litres (64 ounces) of chemistry, and most tanks for film require from to . Many large tanks come with floating lids to reduce possible oxidation of solution. Also, despite such large chemical volumes, some tanks do not allow very many films to be processed at a single time; generally six to ten or so. However, film hangers that hold four sheets of film when used in