To maintain developing stability, to decrease a red tone which appears in a medium exposure part, and to prevent corrosion in aluminum on the surface of a base body in a developing method of a photosensitive planographic printing plate with a replenisher supplying method by using an alkali metal silicate-contg. developer.
(1) The printing plate is developed in such a soln. that the molar concn. ratio of [SiO2]/[alkali metal] is between ≥0.15 and <0.5, the concn. of SiO2 is 1.0 to 3.0wt.%, and the developer contains ≥1.0% org. acid. (2) Changes in the developer due to the development specified by (1) is compensated by replenishig with a soln. having the molar concn. ratio of [SiO2]/[alkali metal] between ≥0.15 and <0.5 and the concn. of SiO2 between >3.0% and ≤4.0%. (3) Changes in the developer due to development is compensated by replenishing with a soln. having the molar concn. ratio of [SiO2]/{9146/28}alkali metal] between ≥0.15 and <0.5 and the concn. of SiO2 between >3.0% and ≤4.0%.
NAKAI HIDEYUKI
HIRAI YOKO
