Abstract: A pattern capable of reducing thereon a precious metal is generated on a suitable substrate by first coating selected portions of the substrate with a solution, called a photopromoter, which contains a metal salt. The metal salt possesses two characteristics:(a) the oxidation state of the salt (i.e., of the metal ion) is alterable (either increasable or decreasable) by exposure of the salt to radiation of the proper wavelength; and(b) in either the original or the altered oxidation state (but not in both states) the salt is capable of reducing a precious metal, e.g., a metal of the platinum group such as palladium, platinum or rhodium, from a salt thereof.The photopromoter-coated substrate is next selectively exposed to the proper wavelength radiation to produce a pattern of the photopromoter salt capable of reducing the precious metal. The remainder of the salt is incapable of reducing the precious metal.