Bronze casting

The casting process for bronze casting

Two main casting processes are used for bronze casting: the sand casting process and the wax casting process. Both processes are "lost mould" processes, i.e. only one casting is possible with this mould, as it must be destroyed after casting in order to remove the finished bronze object. The lost wax process is also a "lost mould" process, as it is made of wax, also known as "lost wax".

Sand casting process

The sand casting process is comparatively simple: an original object or master model is moulded directly in a special, oil- or water-bound moulding sand – the model can then be removed again, so it remains intact. The cavity in the moulding sand is provided with sprue and venting channels, which are drilled into the sand so that the bronze can flow in and air can escape if necessary. Finally, the cavity is filled with molten bronze. The mould can consist of one or more parts.

 Unlike the lost wax process, it is not possible to cast very complicated objects or sculptures with many undercuts. The sand casting processis very suitable for reliefs and simple moulds. Objects or sculptures up to a diameter of approx. 3 cm can be solid cast. Hollow moulds can also be produced using the sand casting process.

Once the bronze has solidified and cooled, the sand is removed and the casting mould is destroyed (lost mould), i.e. only individual casts can be made using the sand casting process. The sand can then be reused. Depending on the number of bronze casts made with the same sand, the sand may need to be reconditioned (regenerated) after a certain time, as its pressure resistance and mouldability diminish.

Lost wax process

The lost wax process is much more complex than the sand casting process and involves significantly more work steps. However, this process can also be used to cast very complicated moulds with many undercuts.

Occupational safety

Melting and casting metals and alloys generates very high temperatures, over 1000° C for bronze casting. Ensure that your workplace is suitable for bronze casting work and that all fire safety regulations are observed. Wear suitable protective clothing at all times! When working with high temperatures, never wear clothing made of highly flammable materials.

When working with a melting furnace, make sure that no moisture can get into the molten metal and that all materials and tools are dry before they come into contact with the molten metal. Ensure that there is a suitable container under the furnace in case molten metal needs to be collected.