Metol(Elon) Developing Agent is used as a developing agent, usually with hydroquinone, but sometimes by itself as in Kodak D-23.
Although metol is easily soluble in water, it is not soluble in a strong sodium sulfite-solution. It does dissolve readily in a weak solution of sulfite. Metol bulds image detail rapidly, and it keeps well in solution.
Metol has low-fogging tendencies and responds well to the addition of bromide, giving a very clean-working developer without any staining of film or fingers.
The energy of the developer is only slightly affected by low temperature and is only slightly reduced by the addition of bromide.
Metol alone with either sodium or potassium carbonates give a rapid working developer when the alkalies are in high concentration, but the speed of the development can easily be controlled by dilution.
The use of caustic alkali (e.g., sodium hydroxide) is not recommended with metol as there is a tendency to excessive fog. When used with sulfite alone, without additional alkali (Kodak D-230, metol provides a slow-working, fine-grain developer. This type of film developer often works well with a mild alkali, such as borax, which accelerates the rate of development without increasing the grain size appreciably (Kodak D-25).
Developers containing metol as the sole developing agent are not widely used but metol with hydroquinone provides the most widely used developer combination.