Bronze casting is used in many different ways and many different reasons. For now, we’re going to take a look at how it is used with sculptures.
The First Step
Bronze casting can only take place when a sculpture has been completed. Once it is complete, the sculpture is divided up into sections. This makes it so much easier to work with. Specialist saws will be used but the type of saw will depend on the size of the sculpture. If the sculpture is of a person, the arms, legs, head, and torso will be cut off. Any other forms that aren’t attached to the body will also be removed.
The Second Step
A rubber mold is now made from the original clay so every detail is captured. It is then prepared using layers of fiberglass cloth and silicone rubber. The next step is to add additional support. Once the support has been added, the clay is removed.
The Third, Fourth, and Fifth Step
The next step is to fill the mold with molten wax. This produces a casting. The castings are also known as a “Wax pattern”. When the wax is cooled, it is removed and hand-finished so it matches the sculpture. Step 5 involves using wax rods and applying them to the wax.
The Sixth Step
Now it’s time to start the shell casting process. The wax image will be dipped in a mixture of slurry and silica sand. This is a process that tends to take at least a few weeks. Once it is hardened, the poured bronze can detect very fine details such as fingerprints.
The Seventh Step
At this stage, the mold is placed into an autoclave. The ceramic will be left to bake, and the was will burn away. This will leave a completely hollow cavity. If any wax remains, it will be steamed out of the mold. When the molds are cooled they will be checked for cracks.
The next stage is to heat bronze ingots so they become liquid before the bronze is poured into the mold.
The Eighth Step
As soon as the sculpture is cool, the mold will be hammered and chiseled. This is to ensure that the bronze sculpture is revealed.
The Ninth Step
Now it’s time for sand particles to be blasted at the sculpture. These particles are blasted using air pressure and they’re used to remove any last traces or the ceramic shell.
The Tenth Step
An artisan will now take a close look at the raw casting. It will be their job to cut away the sprues and gates. The next stage is for the artisan to weld the bronze parts together. This is carried out by using air tools. When the pieces are all welded together, they will be completely aligned. At this stage, it is often necessary for the artist to work on some of the areas. This is to ensure that they look exactly right. Now, the sculpture is blasted with glass beads so the surface has a better finish.
The Eleventh and Final Step
It is now time to treat the sculpture with acid so it becomes the artist’s color of choice. 2-3 layers of a protective coating are added, helping to seal in the color whilst also helping to prevent oxidization. Stainless steel pipes are then welded inside the sculpture. The pipes are placed there so the sculpture is ready to be installed.
As you can see, the process of bronze casting a sculpture is a complex one. However, at the end of the process, you could be left with a sculpture that could last hundreds of years.