Bronze casting is a technical process used to make sculptures or models for centuries. The most popular method is low-wax casting which was discovered in the third millennium. The process has been rediscovered from time to time through experiments with various materials. Bronze is a metal that denotes eternity. Bronze artefacts are passed down through generations.
Introduction
The art of metalworking techniques like bronze casting has been applied for centuries to make everything from sculptures and utensils to jewellery and ornamental items. By pouring molten bronze into a mould that has been made, bronze can take on the shape of the mould and solidify.
Over time, different methods and techniques have been developed for the bronze casting process to produce different kinds of objects with varying degrees of complexity and detail. Bronze casting is still used in many fields today, including the arts, architecture and commercial manufacture.
In this article, you will learn the process and uses of bronze casting, as well as its development and history.
Did you know? Bronze is more expensive than silver! This is because it is more difficult to obtain and needs to be processed well before use.
History of Making Bronze Sculptures
A beeswax artist wrapped a vision in liquid clay and baked it over a fire to make the first bronze sculpture. Since then, bronze sculptures have been created using the low-wax casting method.
Egyptians were the first copper miners. The island of Cyprus, from which the name "copper" derives, was their primary supply.
The Phoenicians were renowned seafarers who had access to copper from Cyprus, Arabia and other locations, as well as tin from Britain and both these metals, as well as zinc and lead from Spain.
They became skilled bronze artisans and spread their craft to many countries.
Unfortunately, they also led to the loss of some early and outstanding bronze art, as metal was always in demand for the creation of weapons. Tin and copper were gathered, heated and poured into a fire-hardened clay hole.
Ancient social structures, cultures and religions are depicted in antique bronze castings. Bronze became popular as it was one of the earliest metals used to make a lot of objects considering its strength and appeal.
Also Read: All About the Ceramic Manufacturing Process in 10 Steps
What Makes Bronze a Good Choice for Making Sculptures?
Bronze is the most commonly used metal for casting sculptures due to its versatility and ease of casting. It expands before the setting, bringing even the most minor details to life.
It also shrinks as it cools, making removing the finished cast from the mould easier. It is convenient to use as it melts at lower temperatures than most metals due to its copper composition.
It is also an excellent material for casting musical instruments, weapons, medals, industrial parts and other items apart from sculptures.
Further, it is corrosion-resistant, making it a long-lasting option for sculptures and other applications.
Bronze Casting Process
Bronze casting requires a high level of skill, and different types of casting processes, including lost-wax casting, investment casting, sand casting, and centrifugal casting, may be used.
For centuries, bronze casting has been used to create sculptures, jewellery and other decorative objects.
The process includes melting bronze and pouring it into a mould to create the desired shape. The entire process takes three to four months to complete. It is a time consuming and highly skilled process.
Handling very high temperatures is dangerous and requires precision.
Let's see how to make bronze sculptures.
Step 1: Artwork Inspiration
Every sculpture begins with an idea and a design in our minds. To bring the project's vision to life, one must investigate the sculpture's history, meaning and purpose. For commissioned projects, designs must be approved before making the clay mould.
Step 2: Sculpting in Clay
Sculptors create a "bone structure" or armature by working with models and references. The piece is then divided into separate sections to ensure proper alignment and re-join each piece precisely. The size and complexity of the piece determine the number of divisions that need to be created.
Step 3: Clay Sculpting Step
To create the mould, liquid silicon rubber is applied to each section of the clay piece. The cured silicon is put in a plaster mother mould to keep the form in place. Moulds are designed like a "walnut shell" with two halves joined by a seam.
They are used to duplicate sculptures in a limited edition and are destroyed once the entire edition is cast. Before retirement, the moulds are only used once for one-of-a-kind pieces like 'They Breed Good Horses’.
This ensures that the artwork's uniqueness is preserved and no reproductions are made.
Step 4: Final Touch
When the wax cools down completely, it is taken off the mould. It is sculpted using various tools, such as dental and heating, to match the sculpture precisely. The artist supervises and adds the finishing touches.
The final product needs to represent the original sculpture accurately. When finished, the wax casting can be used as a mould to make a final bronze sculpture.
Step 5: Creating the Gating System
Molten bronze needs to be poured through an opening. The opening and channel created for this purpose are called Gating.
There must be a way for the gasses to escape. Sprues and branches are made using wax to allow for a clean flow of the molten liquid.
Step 6: The Shell Casting Process
The wax image is dipped into a mixture of silica sand and slurry to begin the investment shell casting process (a highly complicated glue-like mixture called liquid colloidal silicone). It takes a long time for the cast to cool and solidify completely.
It then forms a rock-like hardness that can withstand the extremely high temperature of the molten bronze. Highly complex parts, such as 12-inch fingers, can be cast in bronze. It even allows you to put more complex details like fingerprints and moles.
Step 7: Baking
Ceramic moulds must be baked at a very high temperature to become heat-resistant. For this, a special kiln called an autoclave is used. This completely burns out the wax, leaving the hollow mould to be filled.
Any remaining wax is steamed out of the mould to clean it. After the moulds have been waxed, they are cooled and checked for cracks.
Also Read: What is Electroplating 101? Procedures for Metal Plating
Applications of Bronze Casting
The bronze casting process has beneficial applications, which are:
1. For Artistic Sculptures: It makes an easy choice for artists and allows them to create sculptures that can be intricate and very long-lasting.
2. Jewelry Making: Many jewellery is made using the Bronze Casting process. It is used to create intricate traditional designs.
3. Marine Industry: Bronze casting is used in the marine industry to create propellers, ship fittings, and other components that require high strength and corrosion resistance.
4. Aerospace Industry: Bronze casting is used in the aerospace industry to create components for aircraft engines, landing gear, and other critical parts that require high strength and durability.
5. Automotive Industry: Bronze casting is used in the automotive industry to create engine components, transmission parts, and other critical components that require high strength and wear resistance.
6. Musical Instruments: Bronze casting produces musical instruments such as cymbals, bells, and gongs. The process allows for the creation of unique and high-quality sound.
The bronze casting process is widely used in various industries due to its versatility, durability, and strength.
Conclusion
Bronze is a metal that is easy to use and has longevity. It has been used for dramatic commemorations of rulers, military heroes and famous national historical figures rather than for magnificent sculptures.
Bronze sculptures also depicted gods and goddesses in ancient civilisations such as Greece and Rome. Bronze sculptures, especially those created by famous artists, are precious and treated as family heirlooms. The higher the price, the more likely the likelihood that it will be an excellent investment.
However, before purchasing, you should conduct extensive research. With proper care and maintenance, bronze can be a timeless piece suitable for use as a home decoration that lasts several lifetimes.
Follow Khatabook for the latest updates, news blogs, and articles on micro, small and medium enterprises (MSMEs), business tips, income tax, GST, salary, and accounting.
