The Casting Process:
Creating a Finished Bronze Horse
 from a sculpted clay model

The horse is first modeled in clay, shown above and below.

Next the clay model is coated with liquid rubber.

Layers of rubber are added after each coat dries.
After the third coat of rubber, aluminum shims are added to
allow the mold to be opened when it is completed.

Mesh is embedded in the rubber after the fourth coat of rubber,
then more coats of rubber are added to finish the rubber part of the mold.

(Above) Paper shims are added to divide the pieces of the fiberglass Mother Mold.

(Above) The fiberglass mother mold is built around the rubber mold

 Wax is poured into the mold, the wax sculpture is cut into pieces to allow it to make a good casting. A bronze of very much size at all must be hollow in order for the bronze to cast well.  The walls of the wax piece must be relatively thin, 1/4 inch or less.  In bronze casting, a thin bronze is a good bronze because there will be less shrinkage or distortion in the sculpture.
The wax pieces are then attached to a wax cup with wax "straws" or sprews.

(Below) The wax is then coated in slurry and covered with sand

(Below) Successive layers of slurry and sand begin to build a ceramic
or "rock" shell around the wax. 

(Below) The first layers of sand are a fine grit that picks up all of the detail of
the sculpture, even down to the artists fingerprints that were left on the piece.
Then the later layers are a coarse grit to add strength to the shell.

The "rock" or ceramic shell that coats the wax sculpture is placed in a burnout furnace
where the wax is melted out and the shell is heated to about 1800 degrees.
(Below) Loading the burnout furnace.

(Below) placing the lid on the burnout furnace.

Meanwhile bronze ingots are heated in the crucible furnace until they are liquid and also about 1800 degrees.
Then the shell is pulled out of the burnout and placed in a sand filled cart which is wheeled under the crucible.
The liquid bronze is then poured into the shell.
(Below) Pouring the bronze.

The shell is set aside to cool. 
(Below) When it has cooled the shell is broken off to reveal the bronze sculpture.

The piece is then sand blasted to clean it, and any parts that were cut off
to cause the piece to cast better are welded back on. (Shown below)

The welds are ground down and textured in a process called "metal chasing".
A final sandblast and check are then done on the piece to prepare it for the patina.
(Below) The raw bronze sandblasted and ready for patina.
Bronze if left in this state will naturally go darker and darker,
eventually becoming nearly black or, if exposed to water, green
due the the copper content of the bronze metal.

(Below) The finished bronze horse after patina (color) has been applied,
the finish has been sealed with a coat of hot wax, and the piece has been
 mounted on a beautiful walnut wood base.

 (Above) The finished bronze horse sculpture!
To see more photos of this piece, click on the above photo.

Photos taken at Atlas Bronze Casting, Kearns, Utah.