Treatment of diazo-sensitized lithographic plates

Claim 1

A METHOD OF PREPARING FOR PRINTING BY TREATMENT WITH A SINGLE LIQUID COMPOSITION AN EXPOSED LITHOGRAPHIC PLATE HAVING PRINTING AREAS COATED WITH WATER-INSOLUBLE OLEOPHILIC LIGHT-DRCOMPOSITION PRODUCTS OF A DIAZO COMPOUND AND NON-PRINTING AREAS COATED WITH A WATER-SOLUBLE DIAZO COMPOUND; COMPRISING THE STEPS OF POURING ON THE PLATE AN OIL-IN-WATER EMULSION DEFINING SUCH SINGLE LIQUID COMPOSITION HAVING AN OIL PHASE COMPRISING A FILM-FORMER SELECTED FROM THE GROUP CONSISTING OF ALUMINUM STEARATE AND ASPHALT, AND AN ORGANIC SOLVENT FOR SUCH FILM-FORMER, ANS A WATER PHASE COMPRISING WATER, A DESENSITIZER SELECTED FROM THE GROUP CONSISTING OF SODIUM CARBOXYMETHYL CELLULOSE AND GUM ARABIC, AND A LIQUID WATERMISCIBLE GLYCOL CONSISTING ESSENTIALLY OF LIQUID POLYETHYLENE GLYCOL, RUBBING SUCH EMULSION AGAINST THE PLATE TO REMOVE THE WATER-SOLUBLE DIAZO COMPOUND FROM THE NONPRINTING AREAS BY THE WATER PHASE WHILE DEPOSITING AT LEAST SOME OF SUCH DESENSITIZER ON SUCH NON-PRINTING AREAS TO INCREASE THE WATER-ATTRACTIVENESS THEREOF, AND SEPARATING THE OIL PHASE FROM THE EMULSION BY SUCH RUBBING TO DEPOSIT THE FILM-FORMER AS A FILM OVER SUCH PRINTING AREAS TO INCREASE THE INK-ATTRACTIVENESS THEREOF.