Casting Platinum Jewellery Alloys

There are numerous platinum jewellery alloys available today. Two commercially available general purpose alloys that are in common use by manufacturing platinum jewellers are platinum-5% copper and platinum-5% ruthenium. In South Africa, the copper alloy is normally preferred for casting because of its lower melting point and greater fluidity, while the ruthenium alloy is preferred for hand-working and machining, although some jewellers use either alloy for all applications. In order to provide a scientific basis to the differences in finish and workability, as experienced by jewellers, we set out to compare casting characteristics of platinum-copper and platinum-ruthenium jewellery alloys and look for any substantial differences between them. We also examine factors affecting their different characteristics, and how working conditions can be manipulated to optimise the performance of each alloy in jewellery manufacture.