Polymeric films cast from a polymer solution can develop a bulk porosity, if the conditions are favorable for phase inversion (PI), a physical chemical process based on fluid-fluid demixing of which there are two known major variants: wet and dry PI. As the formation of polymeric coatings often involves a polymeric solution or gel precursor, dry or wet PI phenomena may affect the structure formation of the final solvent-free coating. In this article we identify the situations under which lithographic films can develop a PI structure and focus on solid polymer layers undergoing postcasting wet processing. Examples are provided from the wet processing of a fractionated epoxy novolac resin currently used in lithographic patterning.