Imagine a picture hanging against faded wallpaper. Take down the picture and, on the wall, you will see a square where the wallpaper has not faded. The outline of the picture frame has been recorded by light shining on the wall. If you come back a few weeks later, the square on the wall, now exposed to light, will have faded. Eventually it will vanish altogether.

It was this kind of observation which made people wonder whether light could be made to "paint pictures". There were two problems. First, like the square on the fading wallpaper, the pictures didn't last long. When you brought the pictures into light in order to look at them, they faded. Then, there was the little matter of the exposures which took several hours!

A chemical was found which would stop the image fading. They called it "Fixer" because it made the image permanent. Then someone had the bright idea that though it took several hours exposure for the image to become visible, there must have been some effect on the paper after only a small time even though you couldn't see it. Another chemical was found which could enhance this "latent image". They called it "Developer".

Today, one other chemical is used; "Stop". It stops the Developer working and prevents the Developer contaminating the Fixer.

Negatives and Positives

On a negative the tones are reversed. That is, the places where the original scene was light appear dark in the negative, and where the original scene was dark, the negative is light.

The same thing happens when the negative is printed. This second reversing of tones restores to the image the tones of the original scene.

Developing and Fixing a Film

Wherever light falls on the emulsion grains of silver halide are formed. The Developer converts these grains to metallic silver; the black parts of a negative. Those parts of the emulsion where the light does not fall are still sensitive to light; fixing removes this sensitivity.

You can't develop and fix a film without some equipment! Most lists of equipment would include the following: Developing tank with a spiral for holding the film; Film Cassette opener; Scissors; Measuring Cylinders; Thermometer; Drying clips and a Timer or a clock with a large second hand. (Frankly, some of this is optional! Plastic clothes pegs are quite good as film clips, and a beer bottle opener will double as a cassette opener!)

There is a vast number of films and developers available. To start with, stick to one film and the developer designed for it.

Three factors in processing are of paramount importance. They are Time, Temperature and Agitation; they control the density and contrast of the negatives.

Mix the Chemicals

There are three chemicals to mix; Developer, Stop and Fixer.

All three should be at the same temperature after mixing (usually 20°C); a sudden change in the temperature can cause reticulation. This is a crazy paving effect in the film's emulsion.

The chemicals could come as liquids or powders; the only general instruction is "mix according to the manufacturers instructions".

NOTE: If you live in a hard water area, try to use filtered water and allow a day for the Developer to settle in an airtight bottle before using. Label the bottle with the mixing date and record the number of times the developer has been used.

Load the Film into the Tank

The film must be loaded into the tank in complete darkness and when the tank lid is securely in position normal room lighting may be used and all subsequent steps can be carried out without recourse to darkness.

Ensure spirals are dry. Do not force the film when feeding into spiral as any creases will show as under-developed crescents on the developed film.

Develop the Film

Pour the developer into the tank making a note of the time or start the timer and immediately tap the tank sharply on the bench to prevent air bubbles forming. Invert the tank 4 times over a period of 10 seconds and repeat these inversions at the start of every minute. These inversions are the agitation referred to above. The length of the developing time will be specified in the leaflet which came with the developer. Ten seconds before the time is over, pour the developer into a clean 300ml bottle and, if the instructions say you can use the developer more than once, store in a cool spot for future use.

Stop Bath

As soon as the development time has been completed, pour the stop solution and give constant agitation at the same rate as for the developer. Stop can be reused. Most modern Stop changes colour from yellow to blue when it is exhausted.

Fix the Film

The fixer is now poured in the tank. Which should be agitated as before. At the end of the specified time pour it away. Economically it is not worth saving for the next film unless you are processing two films in the same day.

Wash the Film

This is the last wet stage in the processing cycle. There are two simple ways of washing films but which ever way is chosen it is important to ensure the washing water is maintained within 3° or 4° of 20°C.

The first method is the least tedious and involves having a mixing connection between cold and hot taps which are adjusted to give a water temperature of about 20°C. Direct the flow into the centre if the spiral and leave for 20 minutes.

The second method is to refill the tank every three minutes and continue for 30 minutes giving 4 inversions between changes. Again, the optimum temperature for the water is 20°C.

Finally, fill the tank with water to which has been added a few drops of wetting agent. This speeds up the drying by enabling the water to run off more easily, and also prevents drying marks.

NEVER squeegee a wet film. One piece of grit in the squeegee and you will have scratches down the film's length.

Dry the Film

Finally, remove the film from the spiral, put clips on the ends of the film, and the film in a dust free place to dry. Never dry a film in an airing cupboard as these are invariably dust and lint havens.

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