We’ve all seen at least one bronze sculpture in our lives and admired its beauty. Same as any art form, some pieces are more appealing than others. What’s common for all of them is the process of making a bronze sculpture.
If you ever wondered how a bronze sculpture is made, wonder no more. Here is an introduction to the process of bronze sculpture making. The following method is known as the “lost wax” casting method and it dates back to ancient Egypt.
The original design is made in a material different than bronze. Most artists choose clay, wax, stone, or wood. Nowadays, most artists opt for some type of oil-based clay because it is very flexible for work and doesn’t harden like earth clay. If it is a smaller sculpture, artists tend to use wax. That way they skip the molding stage and use the original piece for casting.
Next, comes the armature which is essential for complex or delicate sculptures. The armature preserves the integrity of the sculpture from breaking or slumping during the making process.
The type armature material depends on the size of the sculpture as well as its complexity. For smaller pieces, a flexible and heavy wire is used, whereas, for larger pieces, makers and artists use large pipes supported by foam.
Sculpting comes after all the armature is in place. At this stage, it’s determined whether the sculpture will be textured, smooth, or a combination of both. Each of them has its own peculiar challenges and each has its own appeal.
Typically, silicon rubber or polyurethane mold is used as a molding material. The molding material is applied with a chip brush. Most times, three to five layers are applied to the original sculpture. On top of the layers, a final “outer jacket”, also known as “mother mold”, is added. Typically it is made from epoxy, resin, or plaster.
After the curing process is completed, the original clay sculpture is detached from the mold. Unfortunately, most times, the original sculpture is destroyed in the removal process.
Certain wax materials need to be preheated before the first layer of wax is added into the mold. The first layer is added at temperatures around 220° Fahrenheit, the second one at about 200° Fahrenheit, while the last coat on temperatures ranging from 180° to 185° Fahrenheit. After the wax is cooled, comes a process known as “chasing”. “Chasing” is a process in which imperfections such as air bubbles are being removed.
Series of solid rods are attached to the individual foundry pieces. They are like channels that direct the molten bronze to flow into the sculpture. Additionally, they are used as vents to get rid of any gases or air.
In this step, the sprued wax is taken to the shell room where another mold is created. There, the wax is dripped eight times into a slurry. Each layer adds strength and thickness.
After the ceramic shell is fully dry is placed into a large kiln in which the temperature is between 1,500° to 1,800° Fahrenheit. At this point, the pour hole is melted by the wax. That leaves you with a highly detailed ceramic mold.
The ceramic shell is taken to the pouring area. There the melted bronze is poured into the ceramic shell.
After the bronze and the ceramic shell is cooled down, the ceramic mold is taken apart. Most times you need sledgehammers to remove the ceramic shell because it is super tough.
Once the raw bronze is freed from its shell, the piece is sand-blasted. That’s done to remove any remaining shell.
This step includes metal chasing. The idea is to create a consistent surface with no imperfections. It is a labor-intensive process that involves a wide set of tools as well as the touch of skilled laborers.
Adding the patina is the last step. It is a complex process in which we add nitrates and oxides at a certain temperature. They are applied with an airbrush, spray bottle, or a patina brush. The final touch is applying a few layers of lacquer.