Which Compound Is Used As A Developer In Photography?

In photography, the developer is the primary chemical in which the processing film or paper is bathed. The typical developer solution is a compound that usually contains the following chemical components: developing agents such as metol, hydroquinone and phenidone; alkalies such as soda, borax and potassium hydroxide; restrainers such as potassium bromide and benzotriazole; preservatives such as sodium sulphite and water.This photographic emulsion is sensitive to light. It contains crystals of silver halides. If these silver halide crystals are exposed to light, sensitivity specks are produced.

Around these sensitivity specks, the developing agents start the process of chemical reduction, which turns the silver ions in the crystals into silver atoms. Big clumps of silver atoms are brown or black and form the image. The developer's activity is increased by the alkali and the restrainer protects the unexposed crystals from developing. Sodium sulphite acts as a preservative and protects the developing agent from reacting with the atmospheric oxygen.

Some developers, especially developers for small and medium-format films, also contain a silver solvent which reduces the size of the silver clumps formed. This silver solvent is usually sodium sulphite, and gives a finer grain. The water swells the gelatine layer and carries the other chemicals into it in solution. Thus the role of the water is one of the most important of all the components that make up the developer.

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