Abstract: A presensitized plate which comprises a roughened and anodized aluminum plate having provided thereon a positive working light-sensitive composition layer which comprises a dye and can be made soluble in a developer upon exposure to light, wherein the dye concentration in the portion of the light-sensitive layer adjacent to or near the substrate is lower than that in the other portions of the light-sensitive layer.The presensitized plate according to the present invention has less color staining than PS plates of the prior art do and thus has excellent examining properties for plate-quality. The presensitized plate also has remarkable advantages of less stains around image-deleted areas during printing and high printing durability.

Abstract: A light-sensitive printing plate precursor is disclosed. The printing plate precursor is comprised of an aluminum support base having provided on a grained and anodized surface. The surface is coated with a layer which is comprised of a positive working light-sensitive composition and an oxonol dye. The printing plate has high printing durability, high water retention ability and high color stain resistance. When used the plate precursor provides an image having high contrast. The plate precursor forms less color stain than conventional plates whether used with a fresh developing solution or a fatigued developing solution. The plate precursor does not result in causing uneven development when using manual development methods.

Abstract: A development method which comprises imagewise exposing a positive acting light-sensitive planographic printing plate comprising an aluminum support and a light-sensitive layer of an o-quinonediazide compound formed thereon, and then developing the exposed plate with a developer, comprising an aqueous solution of an alkali metal silicate, adding a supplementary solution comprising an aqueous solution of an alkali metal silicate to the developer to compensate for the degradation of the developer brought about by development and/or by carbon dioxide in the air; wherein the developer comprises an aqueous solution of an alkali metal salt having an [SiO.sub.2 ]/[M] ratio of from 0.5 to 0.75 and an SiO.sub.2 concentration of from 1 to 4% by weight based on the total weight of the developer, where [SiO.sub.2 ] represents the concentration of SiO.sub.