The ancient lost-wax process.
The origins of the lost-wax process of metal casting are lost in the ancient past more than four thousand years ago, but bronzes today are cast using the very same process. The high cost of a bronze sculpture is due to the many hours of hands-on-labor involved and the complexity of the process to cast a single bronze.
Negative and positive forms.
There are six basic stages in bronze casting turning around the concepts of positive and negative forms. A positive form is the original model such as it has been created by the artist. A negative form is the impression left by this original sculpture when a mold is created holding the sculpture inside.