Sterling silver provides manufacturers and craftsmen with a versatile and reliable material. A disadvantage appears when it is heated in an oxidising atmosphere, allowing copper oxide to form. This oxide penetrates to some depth below the surface and produces a dark sheen, known as firestain. Firestain has been accepted as an inevitable deficiency in sterling silver. In practical terms the labour required to remove or cover up firestain, represents additional cost.

This paper summarises a research project undertaken between Metaleurop S.A. and Middlesex University to explore the use of germanium in sterling silver to prevent firestain. The mechanical properties, corrosion resistance, and welding potential of germanium additions to silver alloys are introduced. Also presented is 1948 research to prevent firestain using aluminium alloyed with sterling silver.

Author: Peter Johns