Following is a visual explanation of how a bronze sculpture is created.
These pieces were cast and finished with the help of sculptor Richard Forbes
The original work is created in clay, plasticine or any other material from
which a mould can be made.
Step one of the rubber mould is to create a wall out of plasticine
around the artwork.
The front half of the sculpture is covered in liquid rubber
and left to dry.
Once the rubber is dry, it is covered in hard plaster that acts as a mother mould. The plasticine wall is removed and the process is repeated on the back of the sculpture. Then the clay is removed.
Next, the mould is filled with hot wax and left to cool. When opened, the mould reveals a positive copy of the original in wax.
The wax positive is then touched up
to remove any seems or bubbles.
The wax positive is coated in a
heat resistant ceramic shell.
The shell is heated in an oven until all of the wax is emptied out.
The recovered wax is saved and
can be used again.
When the oven has cooled sufficiently,
the empty shell is removed.
The cooled shell is planted in a sand pit to await the molten bronze
Bronze ingots are melted in a crucible at 2000 degrees
The liquid bronze is held with metal clamps and poured, by people braver than myself, into the upturned shells.
The bronze is left to cool in the shells
for an hour or two.
When the bronze appears black, it’s cooled.
The ceramic shell is smashed away
with a hammer.
The bronze sculpture is
After sand blasting, the bronze has a
shiny, gold appearance.
Finally, the colour is created by applying a patina solution to the heated metal resulting in a chemical reaction. Once the desired colour is achieved, the metal is cooled with water to stop the reaction.