Abstract: A method is disclosed for removing ink accepting areas of a printing surface of a lithographic printing master by treatment with an atmospheric plasma. Preferably, the plasma is directed to the printing surface as a plasma jet while the printing master is mounted on the plate cylinder of a printing press. The method enables to clean a support of a printing master and then reuse the cleaned support for making another printing master. Preferably, all the following steps are performed on-press: (i) making an imaging material by providing a support with an image recording layer; (ii) making a printing master having a printing surface comprising ink accepting areas by image-wise exposing and optionally developing the imaging material; (iii) starting a pressrun; (iv) a cleaning step using an atmospheric plasma and then repeating steps (i) to (iv).

Abstract: According to the present invention there is provided a method for making a lithographic printing plate comprising the steps of applying a first magnetic field to a dry, light absorbing powder, which comprises a magnetic material and a hydrophobic thermoplastic binder, thereby coating said powder on a surface of a metal support; image-wise exposing to light the powder in contact with the surface of the metal support, thereby increasing the adhesion of the powder to the surface of the metal support, without substantially ablating the powder; and removing the non-exposed magnetic powder from the surface of the metal support under action of a second magnetic field with a polarity substantially opposite to the first magnetic field.

Abstract: According to the present invention there is provided a method for making a negative working non-ablative imaging material, suitable for making a lithographic printing plate, including the steps of applying a dry powder containing at least a compound capable of converting light into heat and an organic compound on a surface of a non-electrically charged metal support, characterized in that the amount of organic compound in the powder ranges from 51 to 95% by weight.

Abstract: According to the present invention there is provided a thermosensitive imaging element for obtaining a lithographic printing plate comprising on a hydrophilic surface of a support a layer comprising an organic metallic salt and in the same or an adjacent layer an organic reducing agent and a compound capable of converting light into heat, said organic metallic salt being reducible on heating by said reducing agent to an ink-accepting compound or to a compound which can react with a hydrophobizing agent to an ink-accepting compound, characterized in that said layer comprising an organic metallic salt comprises a hydrophobic binder in an amount between 0.00 g/m.sup.2 and 0.25 g/m.sup.2 and a hydrophilic binder in an amount between 0.00 g/m.sup.2 and 5.00 g/m.sup.2.

Abstract: The present invention provides a method for preparing an image receiving element comprising an aluminum foil as support comprising the steps of roughening and anodizing said aluminum foil and applying an image receiving layer containing physical development nuclei on said aluminum foil characterized in that said roughened and anodized aluminum foil is posttreated with an aqueous solution containing one or more organic compounds having at least one cationic group.

Abstract: The present invention provides a method for making an offset printing plate according to the silver salt diffusion transfer process using rinsing water, characterized in that alkali is added to said rinsing water before washing at most 20 m.sup.2 of said exposed and developed imaging element and/or before being in use for more than 24 hours in such an amount that a pH in said washing water between 10.5 and 13 is obtained.

Abstract: The present invention provides an imaging element comprising in the order given (i) a hydrophilic grained and anodized aluminum support with an aluminum oxide barrier layer of at least 10 nm thickness, (ii) an image receiving layer containing physical development nuclei in an amount of at least 0.7 mg/m.sup.2 and (iii) a photosensitive layer containing a silver halide emulsion being in water permeable relationship with said image receiving layer. The invention also relates to a method for making lithographic plates with said imaging element.

Abstract: The present invention provides a method for making an offset printing plate according to the silver salt diffusion transfer process using rinsing water, characterized in that said rinsing water before washing at most 20 m.sup.2 of said exposed and developed imaging element and/or before being in use for more than 24 hours is brought in contact with (i) a metal of the group IB or IIB or VIII of the periodic table or (ii) with an alloy containing at least one of said metals or (iii) with a salt containing an ion of at least one of said metals.