Carving a Stone Mould for Bronze Casting — Open-Face and Bivalve Moulds

Before lost-wax casting existed, Bronze Age metalworkers carved moulds directly into stone. Soapstone (steatite) was the preferred material — soft enough to carve with flint tools, yet heat-resistant enough to survive repeated pours of molten bronze at 1,000 °C.

This blueprint covers both the simple open-face mould (one half, open top) and the more advanced bivalve mould (two matched halves clamped together for fully enclosed castings). The open-face mould produces flat-backed tools like axe heads and ingots. The bivalve mould produces symmetrical three-dimensional objects like spearheads and pins.

Alignment notches, vent channels, and pouring funnels are carved to ensure clean castings. A soot or tallow release coating prevents the bronze from bonding to the stone. A well-made stone mould can survive dozens of pours.