Bronze Sculptures

Process and Materials

Bronze sculptures start with an original made of clay or wax that is built onto an armature. The armature represents a ‘skeleton’ of the subject and supports the weight of the sculpting material. Clay is kept damp and workable with water while wax can be cut or shaped with hot metal tools.

Good reference photos or drawings are essential, especially when sculpting portraits, and are used to build an accurate armature. If the armature is wrong the final sculpt cannot be right. Usually a simple form is made out of chicken wire, shaped and fitted over the armature ‘skeleton’ and then covered in plaster which will hold the clay or wax. Again this must be accurate and allow for a reasonable depth of sculpting material, particularly clay; if clay is too thin it will dry out and won’t allow for minor corrections.

Once the sculpture is finished a mould made of plaster, fibreglass or silicone rubber is put over it. The simplest mould is a ‘waste mould’; plaster sections taken directly from the original clay. The clay is removed, the mould re-assembled and a cast poured or laid into it. The plaster is then cut and chipped away to reveal the cast. Fibreglass or silicone rubber moulds are more complex but allow for repeat casts to be made.

For a bronze cast the foundry will first make a wax cast which is then coated in a ceramic material and heated in a kiln to fire the ceramic and melt the wax away. Hence this technique is called ‘lost wax’ or ‘cire perdue’ from the French. The hollow mould is then filled with molten bronze, allowed to cool and the ceramic mould is chipped away. The bronze cast can then be cleaned and polished or patinated.