18 Dec

Pewter casting in high temperature silicone

Every once in a while we like to try our hand at something different, so this time it was casting metal in high temperatue silicone moulds.

We start the process by mixing the two part silicone and pouring that over the object we want to cast. Where the object sits flat, we can make a one piece mould and pour the molten pewter into the mould from the bottom. For objects that do not have a flat side, we need to make the mould two sided. To do that we mount the object in clay (sulphur free as sulphur can react with the silicone and stop it from curing) and pour silicone on to the exposed side. Then when the silicone has cured, we flip the mould over remove the clay, apply mould release to the cured silicone and with the object still in place, we can pour the second side. Don’t forget to add some mating features in the clay to make it easier to align the two halves of the mould.

With the mould fully cured we can remove the source object and where necessary cut in a pour hole and air holes (to avoid trapped air). For a two part mould secure the halves together with elastic bands or a clamp.

Next we melt the Pewter bars. We used a stainless steel kitchen ladel heated with a blow torch.

When there is enough molten Pewter, skim the oxiditation (dross) off the surface with a spoon. Then pour the metal into the mould.

When the mould has cooled down enough you can demold the cast Peweter parts.

Remove any flashing and clean up with files or a dremel and polish with a cotton wheel if you want a shiny finish.

Last Updated on 18 December 2020 by Chaz