How a Bronze Sculpture is made

There is an eternal fascination with the way in which a Bronze Sculpture is created - probably because the process has changed little over the 4000 or so years that Bronze art has existed, although the materials used have improved technically. The end result is completely dependent on the relationship between the Sculptor and the Foundry Master and on the fine interplay between the artistic endeavours of the sculptor and the heavy industrial techniques used by the foundry.

Michael Mawdsley has always worked with Kim Goodwin (+27 (0)33 234 4646) at the Goodwin Foundry in Lidgetton, as have many KZ-N sculptors over the years, since his expertise and that of his team has had an enormous influence on the development of the Midlands artistic community. Kim built his Foundry in 1995, having previously trained as a sculptor and then worked in the Natal Technical College Foundry with Andries Botha and Etienne de Kock for 5 years.

So, how is a Bronze Scuplture made?

The Sculptor creates the sculpture in clay - or in fact it may be created using any number of materials including wood, stone or metal, but whatever is used, the material has to be pliable and useable during what may be a very long period of creativity and refinement. Detail is critically important at this stage. When the creation is complete, it then goes to the Foundry, where the following processes are required to complete the project:

  • Making the Mould
  • Layers of liquid rubber are applied over the sculpture to create a flexible mould which is itself then coated with a fibreglass or plaster “mother” mould to create a supportive shell. Many large sculptures require several parts to make up the whole, so the torso may be done separately from the head or legs, for example.
  • Wax Casting
  • When the mother mould is cured and ready, it is removed from the original sculpture, then re-assembled & filled with molten wax. The aim is to create a perfect, hollow, wax replica of the original so any surface imperfections have to be corrected at this point and if the sculpture is to be a limited edition of, say, 30, then 30 individual Wax Castings have to made from the same mould.
  • Sprueing and Gating
  • Hollow wax rods (gates) are attached to create channels into which the molten metal will be poured and to allow trapped air to escape during the pouring.
  • Creating the “Investment”
  • The Wax Casting replica is dipped in a vat of heat resistant ceramic “slurry”, and then coated in a heat resistant sand or “stucco” to build up the final mould which will eventually take the bronze. This process may take up to a month to complete because there could be as many as 10-12 coats required, and each coat has to dry before the next one is applied.
  • Losing the Wax
  • The ceramic mould (or Investment) is then cut at one end to expose the Gates or channels and is then heated in a kiln to cure and strengthen the shell. This causes the wax to melt and run out - hence the term “Lost Wax” - leaving a space to fill with bronze.
  • Bronze Pouring
  • Molton ingots of bronze, which have been heated to 2200 degrees, are poured into the ceramic shell.
  • The Bronze revealed and finished
  • When the bronze has cooled, the ceramic shell is broken apart and the gate stubs and casting marks removed. This is a highly skilled and labour intensive process and is often referred to as “metal chasing”.
  • Colouring the Bronze
  • The oldest method of colouring bronze was simply to bury the piece, sometimes for several months, to encourage natural oxidisation. Such colouring is called a Patina. Modern techniques allow Patinas to be applied using various chemicals and, sometimes, acryllics. Finally, a thin coat of wax is applied to protect the finished sculpture.