REDUCTION OF COPPER IN SODA LIME SILICATE GLASS BY HYDROGEN

The reduction of copper in soda-lime-silicate glasses by hydrogen was measured as a function of time and copper content within the temperatu re range 440 to 650-degrees-C. Copper is reduced to the metallic state in a surface layer whose thickness increases with time and temperatur e and decreases with copper content. A well developed periodical preci pitation of copper particles is observed in the reduced layer. The red uction is accompanied by an alteration of the glass composition in whi ch there is an increase of the copper content and a reduction of the c alcium content. The growth kinetic of the reduced layer, followed by o ptical spectroscopy and measurement of the layer thickness, is analyze d with regard to the tarnishing model.