BRONZE CASTING PROCEDURE
ARMATURE CONSTRUCTION
 |
Basic construction of the armature is wood and foam. |
| Wire and metal foil is added to insure that clay bonds well to the surface. |
 |
 |
Armature is covered with Non Sulphurated Plasteline. |
MODEL DEVELOPMENT
 |
|
| Various approaches are tested to establish the style of the piece and to achieve the likeness and character of the subject. |
 |
 |
MOLD MAKING (front)
 |
Model is divided into front and back halves with thin metal
shims. Clay dam is built to contain mold material. |
| Several layers of flexible urethane rubber are applied to model surface to a uniform thickness. |
 |
 |
Plaster " Mother Mold " is used to hold the flexible urethane mold form in place. |
MOLD MAKING (back)
 | |
 |
Process used in making the front mold is repeated for the back half. |
| |
BUILDING WAX POSITIVE
 |
Molten wax is applied to the inside of the urethane mold
with a natural bristle brush. |
| Many layers of wax are slowly built to assure uniform thickness of approximately ¼ ". |
 |
 |
Back section is built to same uniform thickness. |
| Wax is released from mold after sufficient cure time to prevent warpage. |
 |
 |
Front and back sections are joined together with molten wax and joint seams are " chased " to appear seamless. |
CERAMIC MOLD
 |
Sprue and vent systems of wax are attached to the wax model by which the heated wax will later flow from the mold and the molten bronze will enter, then the dipping process begins. |
| The wax model is coated with a refractory ceramic material then coated with sand. |
 |
 |
The refractory-sand process is repeated several times over
a period of days under constant temperature and humidity requirements until a desired thickness is reached. |
| After the shell is thoroughly cured the piece is placed in a kiln for hours to remove any moisture and eliminate the wax creating a positive void in which will be poured the molten bronze. |
 |
CASTING
 |
The heated ceramic shell is placed into a steel container and held in place with sand. |
| Molten bronze of approximately 2,200 F is prepared for the pour. |
 |
 |
Pouring molten bronze is a team effort. |
| The cast piece remains in sand allowing the bronze to solidify and the molecules to align in a certain matrix. |
 |
SHELL REMOVAL
 |
The ceramic shell is carefully removed so as not to damage the bronze. |
| As much shell is removed by hand as possible. |
 |
 |
Air tools are employed in interior areas. |
| Sprue systems and vents are removed with carbon abrasive cut-off wheels. |
 |
BEAD BLASTING
 |
100 mesh silica under 100 lb. Air pressure is used to remove remaining shell. |
 |
METAL CHASING
 |
All final remains of the sprue feeder system is removed. |
| TIG welding utilizing bronze rod eliminates any imperfections. |
 |
 |
Separately cast pieces attached with the use of the TIG welder and bronze rod. |
| Metal is "chased" ... ground filed and sanded. |
 |
 |
After chasing process the entire sculpture is again bead blasted to create a uniform surface. |
PATINA PROCESS
 |
Bronze is heated to a uniform temperature of approximately
350 F and a chemical solution is applied in light successive layers to achieve desired color. |
| When the bronze has reached the right color and has sufficiently cooled the waxing process begins. |
 |
 |
Half a dozen coats of wax is applied to assure surface protection. |
 |
 |