Bronze casting, crafted through the "lost wax"
method, has remained almost the same for over 5000 years. The process begins with the sculptor designing their inspiration in clay. It is then turned over to the foundry for the artisans to begin by making a rubber mold of the piece. After the rubber sets up, a plaster mold is made over the rubber to keep it from distorting when the mold sections are taken apart. This is called the "mother mold"
and all details of the sculpture are perfectly imprinted. The mold is
then cleaned of clay, reassembled, and a 1/4" layer of wax is applied to the rubber. The sculpture
is now in a wax form, to which wax rods are attached that lead to a
funnel for the purpose of pouring bronze. The wax sculpture is then
dipped in a silica sand mixture forming a rigid ceramic shell.
Heating in a burning-out oven, the wax is melted away leaving a hollow
shell. This is where the "lost wax" terms applies.
After heating the shell, the bronze, which has been heated to over
2000 degrees F, is poured into the shell. When the bronze has cooled
the shell is broken off with a hammer and the bronze sculpture
remains. (For the sculptor this experience is like Christmas!) The piece
is then sand blasted to remove any of the remaining ceramic shell. The
surface is then chased to remove any imperfection. The patina, color,
is applied with heat using different chemicals. The sculpture has gone
thru many steps and handled by experience craftsman.
version of this process is to think of the clay being a positive form,
the mold as a negative form, the wax back again as a positive, the
ceramic mold as a negative, and finally the bronze as a positive.
Each step is important to ensure a replica of the original