Figure 1. shows the effects of Zn and Si on Vickers hardness of the sterling silver alloys produced by investment and metal mould casting. It is clearly seen that the samples prepared by the torch melting/metal mould route have higher hardness levels than the samples prepared by investment casting. The standard 935Ag sterling alloy cast in a metal mould has a hardness around 66 HV compared to around 56 HV for the alloy cast into an investment mould. The hardness level in investment cast samples is about 5-10 HV lower than for the equivalent samples cast in a metal mould. Independent from alloy composition the Vickers hardness depends on the cooling rate during solidification and isalways consistently
higher for samples obtained by metal mould casting due to the higher cooling rate