and replacing it with another metal from solution all previously known electroless silver plating compositions are poorly autocatalytic and give only a thin silver film of less than 0 25 micron a true electroless bath will plate on a continuous surface of a support metal which does not dissolve in the bath for example an electroless or electrolytic nickel layer to give a thick deposit although the disclosure hereof is detailed and exact the formulations listed in the examples are merely illustrative of useful plating bath formulations any formulator skilled in the art can utilize these examples and this concept to prepare many workable solutions in addition to those shown in the examples test articles were one ounce per square foot copper foil clad epoxy glass laminate printed circuit board material these boards were cut into 2 5 cm by 7 5 cm sections for convenience of use the test boards were prepared for electroless silver plating tests by coating them with a medium phosphorous 6 9 electroless nickel any effective preparation cycle and electroless nickel are suitable the boards were cleaned catalyzed with a palladium chloride hydrochloric acid solution and plated in a standard electroless nickel to 0 2 mils 5 microns thickness the electroless silver plating composition consisted of a solution of 200 g l sodium thiosulfate 20 g l.