Lost Wax Casting
This particular type of casting is time consuming and requires many detailed, precise steps.
Larry Young is one of the few artists in the country with his own foundry, where he can cast metal sculptures up to 17 feet high.
Join the artist in his foundry, where we follow the process step-by-step as he casts his 17-foot bronze sculpture, Nexus, for the Boone County Hospital in Columbia, Missouri.
Step 1
Building an armature to support the clay enlargement of the sculpture.
Using steel covered by chicken wire, an interior support structure is created. The water-based clay is pressed onto the chicken wire.
Step 2
Refining the clay sculpture.
Using a variety of tools, the clay is sculpted into its proper shape. You can see the maquette of the sculpture on a stand on the left side of the photograph. I am using a three-dimensional pantograph that helped to identify where points and edges needed to be on the enlarged clay.
Step 3
Making final preparation for remaining mold sections.
A plaster mold is made in sections around the entire clay sculpture. From this plaster mold I can make wax replicas of the sculpture to take through the lost wax bronze casting process.
Step 4
Mold making detail.
Here you can see the clay wall that is attached to the sculpture to form the parting line for the next section of the mold.
Step 5
Making waxes.
The plaster mold section is used to create a wax pattern of the sculpture in Victory Brown wax. The red wax rods provide support and a flow pattern for the molten bronze. Everything you see here in wax will eventually be melted out from inside a special mold.
Step 6
Making waxes.
The plaster mold section is used to create a wax pattern of the sculpture in Victory Brown wax. The red wax rods provide support and a flow pattern for the molten bronze. Everything you see here in wax will eventually be melted out from inside a special mold.
Step 7
Allowing the investments to dry.
After the first coat of investment dries, the process is repeated approximately ten more times. Once fired in a kiln this special mold can withstand the high temperatures of molten metal.
Step 8
Melting the wax out from inside the mold.
The waxes are placed inside an 1800 degree kiln. Once the wax is completely gone, there is a strong ceramic shell mold with a hollow space inside where the wax once was.
Step 9
Heating up the bronze.
Using a gas-fired furnace, the bronze is melted and heated to 2100 degrees F.
Step 10
Pouring the molten bronze
The molten bronze is poured inside the hollow space where the wax once was.
After an hour or so, the ceramic shell mold is chipped off the bronze. If the pour was successful, everything that was once wax is now bronze.
Step 11
Welding the bronze sections together.
Once cast, there is still a phenomenal amount of work that remains. The rough bronze is cleaned in a sandblaster. Then, each of the bronze sections are carefully aligned and welded together.
Step 12
Welding the last bronze section in place.
Step 13
Finishing the bronze.
Care is taken to grind each of the welds down to the intended form.
Step 14
Half way through the finishing process
Step 15
Installing the sculpture.
Half of the Nexus is lifted into place.
Step 16
Final finishing is completed on site.
Step 17
Applying the Patina
The final stage of the process involves applying the patina or coloration to the surface of the bronze. Since bronze alloys consist mainly of copper, sculptors usually apply chemicals to the surface of the bronze to cause a controlled chemical reaction that produces beautiful colors that will prevent corrosion if the bronzes are kept inside. Outdoor patinas need to be washed and waxed each year and eventually will need to be redone.
