Sterling silver alloys are comparably soft in the as-cast state (60-70 HV). A higher strength is often required, e.g., for filigree items, and has a positive influence on polishing properties. The hardness of sterling silver alloys can be increased significantly up to ca. 150 HV by suitable heat treatments. Although the process has been well known in principle for decades, it is seldom applied because it is time-consuming, and significant improvements are sometimes not easy to achieve. More recently, new sterling silver alloys have been developed with grain refinement, fire-stain resistance and improved investment casting properties. The as-cast hardness of these alloys is even lower than for standard sterling silver (around 50HV). The presented paper first reviews the basics of strengthening sterling silver alloys by age hardening. This will be followed by an overview on hardening properties of the new sterling silver alloys. The possible influence of different alloy constituents like Zn, Si, Ge, Ir and B will be discussed, as well as the advantages/disadvantages of the new alloys compared to standard sterling silver.

Author: Dr. Jörg Fischer-Bühner