Abstract: The present invention concerns: plates for use in wet offset printing, which have been lightened in an original manner; the preparation of said plates; and their use in the context of wet offset printing. In characteristic manner, said plates comprise two groups of small non ink-accepting lightening surfaces in at least part of their lightened ink-accepting surfaces.

Abstract: The present invention concerns an original method of copying a printing plate. Said plate, intended for wet offset printing, comprises a base substrate and a photosensitive layer which is soluble in a solvent. As is conventional, said method comprises selectively eliminating said photosensitive layer at suitable locations and is characterized in that said selective elimination comprises: depositing droplets of said solvent at said suitable locations; and rinsing the plate to evacuate the deposited solvent, which by then is charged with the photosensitive layer eliminated from said locations and is inactive.

Abstract: The present invention concerns an original method of copying a printing plate. Said plate, intended for wet offset printing, comprises a base substrate and a photosensitive layer which is soluble in a solvent. As is conventional, said method comprises selectively eliminating said photosensitive layer at suitable locations and is characterized in that said selective elimination comprises: depositing droplets of said solvent at said suitable locations; and rinsing the plate to evacuate the deposited solvent, which by then is charged with the photosensitive layer eliminated from said locations and is inactive.

Abstract: The present invention relates to the use of the frequency-modulated screening or stochastic screening for lightening the printing surfaces, in waterless or wet offset printing techniques. It also concerns the films and plates used in these printing techniques which, in characteristic manner, generate printing surfaces lightened by means of a stochastic screening (or frequency-modulated screening).

Abstract: An offset printing plate and method of manufacturing comprising providing a hard, hydrophilic supporting base material of steel, depositing a layer of dull, porous, ink-rejecting chromium directly onto the surface of the steel base material, the chromium layer having a thickness no greater than one micron and being sufficiently thin and porous to permit the desirable properties of hardness and hydrophilicity of the subjacent steel base material to manifest themselves through the chromium layer during printing, and sufficiently thin to permit removal of the chromium layer from a selected area of the offset printing plate by scraping to expose the subjacent surface of the steel base material.

Abstract: An offset printing plate comprising a steel base with two layers of chromium, said layers having a combined thickness no more than 1.mu..

Abstract: The present invention relates to new offset plates wherein the surface of the steel-containing support is coated with a thin water-accepting layer of chromium and chromium oxide.