Abstract: Emulsion developers for diazo-sensitized printing plates are disclosed which are characterized by an oil phase containing a partially water-soluble aliphatic cyclic carbonate having the formula: ##STR1## where n is an integar from 0-2, and Z is selected from hydrogen, C.sub.1 -C.sub.3 alkyl, hydroxyl alkyl or chloroalkyl, chlorine, hydroxy or phenyl. The preferred carbonate is propylene carbonate.

Abstract: A developer is provided for lithographic plates or the like having a layer including a diazonium material, which developer enhances the effectiveness of the photolysis to which the plate had been subjected, with the result that the exposure time needed for the plate is substantially reduced. The developer, which thus enhances the apparent photospeed of the plate, includes an insolubilizing reactant that reacts with diazonium groups of diazonium materials on the plate that were not removed by photolysis during exposure in order to decrease the solubility of the diazonium material.