Method for supplementing replenisher for developer in automatic developing machine for presensitized plate

A method for supplementing a replenisher for developer which comprises developing a large number of presensitized plates for use in making lithographic printing plates, which have been imagewise exposed to light, with a developer comprising an aqueous solution of sodium silicate or potassium silicate in an automatic developing machine, comprising the steps of determining an AC impedance of the developer contained in the automatic developing machine, obtaining a correction impedance from the measured impedance value and rate of replacement and supplementing a desired amount of the replenisher to the developer when the correction impedance reaches a predetermined value, wherein the correction impedance is determined by substituting the measured impedance and a rate of replacement into a predetermined calculation equation as follows:

• Y=X-(-ax.sub.n +b-c)
• x.sub.n =(x.sub.n-1 .multidot.A+B)/(A+B)
• x.sub.o =0
• wherein x.sub.n represents the rate of replacement;
• Y is the correction impedance value;
• X is the measured impedance value;
• a denotes the slope of the rate of replacement to the impedance value (b-c);
• b is an initial impedance value of the developer;
• c is the final impedance value thereof;
• A is the initial amount of the developer;
• B is the amount of the replenisher per supplementation;
• and n is the number of supplementation.