Description

Metol is an excellent developing agent for most continuous tone development applications, and has been widely used in published developing formulas as well as commercial products. However, it is difficult to produce highly concentrated developing solutions using metol, and therefore most metol developers are supplied as dry chemical powder mix. A developer containing both metol and hydroquinone is called an MQ developer. This combination of agents provides greater developer activity since the development rate of both agents together is greater than the sum of the development rates of each agent used alone (superadditivity). This combination is very versatile; by varying the amounts of metol, hydroquinone, restrainer, and adjusting the pH, the entire range of continuous tone developers can be made. Therefore, metol replaces most other developing agents, except for hydroquinone, phenidone (which is more recent than metol), and phenidone derivatives. Notable formulas include Eastman Kodak D-76 film developer, D-72 print developer, and D-96 motion picture negative developer.