The synergistic behavior of MQ and PQ developers of lower pH at which hydroquinone is almost inactive has been examined in the context of pure physical development.
As a vacuum deposited gold layer was used as physical development nuclei, a linear ralationship between the development time and the mass of developed silver held in all developers except in Phenidone developers. The nonlinear relationship in Phenidone developers was found to due to the restraining action of oxidation products accumulated in developers.
The superadditivity of MQ and PQ combinations was observed to occur in pure physical development as large as in chemical development. It can be accounted for by the extended regeneration mechanism as follows. In MQ developers, Metol is simply regarded as a redox catalyst and promote the development reaction. The remarkable superadditivity of PQ combination can be interpreted as the mixed effect of both the catalytic action of Phenidone and the restrainer-removing action of hydroquinone.
View full abstract