Silicones in Jewellery Manufacturing: How materials properties impact on innovative design and production

Investment casting, also known as lost-wax casting, is a well-known process widely used in many industrial sectors. In particular, it represents the main technique used for the production of jewellery items. One of its main strengths is the flexibility in terms of different castable patterns ranges, basically due to the use of wax models. The production of the wax models, to be replicated during the casting, is traditionally carried out via wax injection and, for this purpose, rubber moulds are used in the process. They were historically made up of natural rubber and, particularly in the last decade, are obtained using silicone rubbers. Jewellery industry, being related to fashion, is more and more focused on the use of new materials, basically in order to get thin and intricate shapes, hollow parts and innovative design features. This is leading to a substantial updating and upgrading of the process, with a constant innovation regarding technologies and modification of traditional materials. In this frame, a starting good quality wax pattern is the key-point for the optimization of the following processes. Aim of this work is the definition of a proper silicone/set of silicones with targeted properties in terms of strength, hardness and thermal conductivity, able to improve the control on the final quality of the injected wax patterns. The chance of getting a polymer based material showing high conductivity could open once verified new perspectives for the manufacturing of so far impossible-to-be-made-objects following the traditional processing (i.e: extremely thin filigrees) or for an easier processing of difficult-to-inject components (i.e: thick or massive parts). In case of the former components, a high thermal conductivity is the only possibility to get the parts, given the chance of controlling (and therefore tuning) the temperature of the silicone mould during the wax injection.