Casting - Investing

The next stage is to embed the wax tree with a refractory material that will become the hot mould for the metal casting phase.

For Gold and Silver alloys the refractory material is Gypsum based. This is just like plaster of Paris in appearance and performance, however, there are special additives for high temperature performance. When the Gypsum moulds have set, the rubber bases are removed and the whole mould is placed in a steam dewaxer to remove the bulk of the wax. This process results in better quality castings than trees that are placed directly in the furnace for the whole burnout cycle. When de-waxing is complete they are placed in a pre-heated furnace.

For Platinum casting a special Phosphate bonded material is required which is very pedantic regarding mixing requirements. The whole process is carried out under vacuum to get the optimum results. This material does not fully set at room temperature, and will not withstand steam dewaxing, so these flasks are placed directly into the furnace for the burnout cycle.