When the developer is prepared with tap water, the solution usually appears cloudy, which fact is due to the lime salts of the water combining with alkali and forming a precipitate. This turbidity has no effect on the properties of the developer, but if the lime content of the water is high, it may result in an unpleasant deposit on the surface of the film.
In such cases the chalk precipitate should be allowed to settle, or the solution should be filtered before use. The formation of lime deposit may be avoided by the
addition of certain substances to the developer. The following are recommended :
- Calgon (sodium hexametaphosphate)
- 1 gram to 1 litre should be included when the sulphite is added to the developer solution.
- Sodium metaphosphate
- Prepare a 1:10 solution and add 3–5 mililiter per litre to the water that is to be used for making up the developer. It is essential that this solution is added to the tap water and not to the ready-made developer.