How a Photographic Film is Developed

How a Photographic Film is Developed

You surely remember the cameras from the 80s that used to actually have a film, but do you know how this film is developed? We, for our part, have always been wondering how this is achieved and have finally received the chance to find out more about the techniques of developing a photographic film. Now we will take you on a behind-the-scenes tour of the entire process.

There are several development processes that can be used to develop the photographic film and we have chosen to explain the developing tank. Most of these methods only differ in the containers that are used for carrying the chemicals. They use, however, more or less the same chemicals in the actual process. The developing tank is more convenient since it allows photographic films to be developed in a daylight environment instead of a darkroom.

To begin the process of converting the latent image into a visible picture, the film needs to be loaded onto a film reel. This, however, has to be done in a completely dark environment since any light contact could result into badly developed pictures. Once the reel is loaded, it is put inside the developing tank. Then, the lid is screwed onto the tank which allows to continue the process in the daylight. In order to dissolve the outer layer of the film, the film needs to soak in cold water.

The outer layer is simply a very thin skin of gelatin  which is sensitive to water and protects the film from any scratches during the handling. After the protective layer is dissolved in water, the film is exposed to the developer solution. The solution’s primary function is to make the latent picture visible. The developer solution is comprised of a combination of chemicals, consisting of alkali and metol or hydroquinone mixed with water. One chemical within the developer solution, namely metol, reduces the sub-micron sized grains of silver halide crystals in the emulsion to black metallic silver. The developer solution has to be diluted with water according to the measurements. Once the developer is poured carefully into the tank and the push-cap is placed on top of it, the whole tank needs to be slowly flipped a few times.

After this, the developer has to be poured out completely for the next step.  The next crucial step in the developing process is the stop bath. This bath consists of a glacial acetic acid, usually around one to two percent, or water. The purpose of the stop bath is to simply halt the development of the film. There are two ways for achieving this. One way is by rinsing out the solution with water. However, during the rinsing the developing process continues at a low level for an uncontrolled period of time. If an immediate stop of the development is desired, the stop bath consisting of a glacial acetic acid is used.

This bath neutralizes any excessive development of the silver crystals when alkalis and acids are mixed together. The neutralization of the alkalinity of basic developers can help to preserve the strength of the fixer. The function of the stop bath is highly important since an overdevelopment of the silver crystals results in an image that is virtually impossible to discern. Pouring the stop bath into the tank needs to be done exactly the same way as with the developer solution.

A developing process, however, cannot be finalized without the fixer. It is a chemical mix and often also called hypo, which is the abbreviation of “hyposulphite”. In most cases, the unexposed silver halide remains on the photographic film and thus becomes sensitive to further action by light. Therefore the fixer is very important as it stabilizes the image and makes it light-resistant by dissolving the remaining silver halide salts. After the unexposed silver crystals are removed, the fixer then hardens the remaining crystals in the emulsion. This is the process that enables to preserve the photographic image over time.

Once the film has been developed, the process needs to be completed with two steps. Firstly, the film needs to be carefully rinsed with water in order to remove all the chemicals used in the steps before. If any chemicals remain, a deterioration of the image could be caused. Lastly, the film is dried in a dust-free environment, cut and placed into protective sleeves and finally ready for viewing.

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