Abstract: A sharp imaging, non-smearing system for latent imaging and subsequent visual development of printed text or the like is provided which can be used on a variety of substrates (e.g., paper, metal, cloth, synthetic resins) and is extremely stable and easy to use. The system involves first imaging a substrate with an invisible ink containing a dissociable transition metal salt such as CuSO.sub.4, with subsequent application of a liquid developer containing a solubilized color precursor such as thiooxalic amide which complexes with dissociated transition metal ion to give a sharp, virtually instantaneously developing, long lasting color. Depending upon the metal salt selected, different colors can be obtained upon development. The system of the invention can be used in a variety of contexts, such as in self-testing materials or novelty items.

Abstract: A method and apparatus for the selective deposition of metal layers on a substrate. At least one metal layer is deposited in a self-aligned manner on conductive regions on the surface of isolating or semiconductive substrates, for which purpose the conductive regions are arranged facing a metal plate having at least one layer of the metal to be deposited, and Tesla currents are generated between the metal plate and the regions to be coated. The apparatus for implementing the method includes a metal plate, a Tesla transformer which is coupled to the metal plate or to a metal grid, spaced apart from the surface of the metal plate away from the conductive regions, having closely adjacent and regularly distributed spikes pointing towards the metal. This method may be used, for example, to produce conductors on or in ceramic modules, circuit cards and semiconductor elements.

Abstract: According to this method, copper is dry etched in a glow discharge containing compounds with at least one methyl or methylene group, particularly at temperatures close to room temperature.The method is applied in particular for making conductors on or in module substrates or circuit cards, solder spots, and the wiring of magnetic thin films.