A method of making imaged elements such as lithographic printing plates is achieved by imagewise exposing an infrared radiation-sensitive positive-working imageable element to provide exposed and non-exposed regions. The imaged element is developed using a single processing solution having a pH of from about 9 to about 11.5 and containing carbonate ion and at least 1 weight % of one or more anionic surfactants, to remove predominantly only the exposed regions to provide an image and to provide a protective coating on the imaged surface. The imageable element comprises a substrate and a radiation absorbing compound, and has an imageable layer on the substrate that comprises a developability-enhancing compound and a poly(vinyl acetal) in which at least 25 mol % of its recurring units comprise pendant nitro-substituted phenolic groups.