Abstract: Process for formation of a hardened, insoluble or crosslinked stencil or resist image on a substrate, e.g., having a metal surface such as copper, and modifying the substrate or image surface comprising:A. forming an image on the substrate by applying a solvent-soluble thermoplastic copolymer of ethylene and .alpha.,.beta.-ethylenically unsaturated acid having an acid number of at least about 30, the copolymer reacting thermochemically with the substrate;B. fusing at a temperature and for a duration to induce the thermochemical reaction at a rate sufficient to partially insolubilize, harden or crosslink the polymeric image and adhere the polymeric image to the substrate surface to facilitate subsequent removal therefrom;C. modifying the uncovered substrate surface or the polymeric image surface, e.g., etching, plating, depositing, soldering; andD. removing the polymeric image.The image can be formed on the substrate by printing, electrostatic means, etc.