Abstract: A composition for improving the ink receptivity of lithographic printing images comprises an organic solvent liquid capable of softening the surface of the printing image and a film forming alkali-resistant oleophilic material such as a liquid hydrocarbon solution of a normally solid hydrocarbon or fat. The composition is for use in the case where the printing image is formed by alkaline development of an image-wise exposed radiation sensitive coating such as a phenol formaldehyde resin in admixture with a sensitiser. The composition may be applied before exposure to form an alkali resistant oleophilic layer on the radiation sensitive coating or it may be applied after image-wise exposure but before alkali development.

Abstract: The amount of water present on a lithographic printing plate during printing is determined by measuring the amount of water present on a surface which is other than that of the printing plate but which carries an amount of water related to the amount of water present on the printing plate. The surface upon which the measurement is made may be the surface of a control pad mounted on the printing roller in the gap between opposite ends of the printing plate, the surface of one of the rollers of the damp train applying water to the printing plate, or the surface of an auxiliary roller contacting one of the rollers of the damp train applying water to the printing plate. The amount of water subsequently applied to the printing plate may be regulated in dependence upon the amount of water determined as being already present on the printing plate.

Abstract: A desensitizing composition comprises an aqueous solution comprising (i) a polymer containing structural units derived from acrylamide and from 1% by weight to 25% by weight of structural units containing carboxyl groups and (ii) desensitizing acidic material in an amount such that the pH of the solution is less than 5.5. The carboxyl group containing structural units may be derived from acrylic acid and/or an acrylic acid salt and the desensitizing acidic material may be phosphoric acid. The composition may be used as a substitute for gum arabic solution in lithographic plate making processes and lithographic printing processes.