White golds: A question of compromises

Abstract

The initial review of white gold research, summarized at the 1992 Santa Fe Symposium on Jewellery Manufacturing Technology was extended into an investigation of the physical properties of numerous white gold formulations. Attributes such as colour, hardness, melting temperature, tensile strength, cold working performance, investment cast form filling, fire-cracking tendency and nickel allergy response were quantified. Properties of experimental alloys developed from the work of previous studies or new combinations of elements were compared to nickel bleached carat gold materials. Secondary base metal bleaches such as iron and cobalt did not improve the performance of nickel white golds. Formulations based on the bleaching action of palladium combined with copper exhibited comparable or improved physical properties and commercial viability. Free from nickel, with significantly reduced melting temperatures compared to palladium-silver formulations, these materials were directly compared with conventional carat alloys. Positive opinions from field testing reinforced laboratory results. Nickel remains the least expensive commercially viable bleach of gold. The cost of palladium additions is a detrimental factor restricting widespread application for high volume, low cost jewellery. Where the unique properties of palladium white golds are beneficial for hand crafted items, their additional cost can be justified.