For higher production volumes and more aggressive polymers, it is critical that the tool material has a high degree of mechanical hardness.

Using molten metal casting techniques, it is possible to cast around an accurate pattern with either aluminum- or zinc-based alloys with a two-week leadtime.

Given the casting temperature of both aluminum and zinc it is important to replicate the initial pattern into a material capable of withstanding such heat. Using silicone tooling, as detailed earlier, a cavity is produced around the model. However, rather than a resin copy being made, the silicone cavity is then filled with ceramic. After drying, the ceramic facsimile is placed into a bolster and covered with the molten metal.
Cast aluminum and zinc kirksite tooling offer a simple and low-cost method of tooling. Disadvantages include a distortion of tools, accuracy problems due to shrinking, and geometry limitations (i.e., no fine features).