The present invention discloses a continuos process for the partial demetallization of a first multilayer substrate, comprising at least one metallic layer 21, characterized in that a designed lacquer comprising at least one metal dissolving etchant 25 locally reacts with said metallic layer 21 and that the dissolved metal remains within said multilayer structure and that the dissolution of the metal allows the creation of a window in said metallic layer without the necessity of a washing step and in that said partial demetallization is suitable to be carried out on standard gravure or flexo printing presses or coating equipment.