How Bronze Sculptures Are Made From Clay – Lost Wax Casting

Lost wax casting process that was used to create bronze sculptures centuries back has remained unchanged for ages. Ancient Greeks and Romans primarily made sculptures either of bronze or marble due to their remarkable beauty and durability. In ancient Asia, Egypt, Africa and China, lost wax method of casting bronze sculptures was prevalent. There have been found bronze sculptures from as far back as 310 B.C. – The Victorious Youth from Greece dates 310 B.C., Brunswick Lion from Germany dates 1166, and The Orator of Etrusco-Roman dates 100 B.C. Bronze was then used for creating stunning sculptures that stood the test of time. The same lost wax casting is still widely used in the 21st century to create beautiful bronze sculptures and art pieces.
Lost Wax Bronze Sculpture

What is Lost Wax Casting?

‘Lost wax’ is the term given to the process of creating a bronze sculpture from clay. The wax melts away at a certain stage in this process, giving it its name ‘lost wax’. The process itself is laborious and has a number of steps. To understand how a bronze sculpture can be originally created from clay, let us look at the complete process.

Step 1 – Creating the Original Clay Sculpture

The artist first creates the sculpture in clay. Depending upon the artist’s preference, oil-based clay, water-based clay or self-hardening clay can be used to create the model. The original clay model is created with all details that are required in the bronze sculpture. In case of large sculptures where the clay might slide off the surface due to its weight, armature (a skeleton made out of wire, aluminum, etc.) is used as support.
Lost Wax Process

Step 2 – Applying Rubber Layers

After the clay sculpture is created in all its perfection, multiple layers of Polyurethane Molding Compound or silicon rubber are applied to it. These layers of rubber are put directly on the clay surface. When the first layer of rubber dries, the second layer is applied, and so forth. Completion of this step can take several days.

For large sculptures, separate moulds are created for each part of the sculpture. For example, the head will have a separate mould, the torso another and the legs another. Later, when the sculpture is finally ready in bronze, the different parts are joined together.

Step 3 – Making a Wax Replica

Molten wax is now poured into the mould from a hole at the top. The wax is poured in stages, at different temperatures so that it covers the inside surface of the mould properly. Since the wax replica needs to be hollow from the inside, only sufficient wax is poured so as to cover the inside surface of the mould. When the wax cools, the hollow wax replica is removed from the mould.

Step 4 – Putting the Sprues

In preparation of pouring molten bronze, wax rods called sprues are attached to the wax replica. Sprues allow molten bronze to reach the different areas of the sculpture and also make a channel for trapped air to escape. Special care is taken of areas that are difficult to reach.
Clay to Bronze Sculpture

Step 5 – Creating a Ceramic Shell or Investment

Next, a ceramic shell is created by dipping the wax model into a heat resistant mixture called slurry. When it is dry, it creates a hard exterior to the clay model, which will later hold the molten bronze as the wax melts away. Since this part of the process is just prior to the pouring of molten bronze, extensive care is taken to get the details right.

The wax model is dipped into a solvent to clear it of any dust, dirt or debris. It is then dipped into another solution (prewet) and layered with extremely fine slurry. After this coat has dried, it is put into different types of slurry to create from six to twelve coats. This part of the process is time consuming and may take from one to two weeks to complete.

Step 6 – Melting of Wax

Now that the ceramic mould is ready, the wax is melted away by placing the mould in high temperatures. The melted wax becomes “lost” and the ceramic shell becomes harder and stronger. This losing of wax has given the process its name ‘lost wax’.
Bronze Sculpture Foundry

Step 7 – Pouring Molten Bronze

Bronze is heated at temperatures of approximately 2200 degrees Fahrenheit to create liquid bronze. Very carefully, molten bronze is poured into the ceramic shell through sprues. It is then left for cooling. For more information about metal casting and the ‘lost wax process’ please click here.

Step 8 – Breaking the Ceramic Shell

When the molten bronze and its ceramic shell have cooled down, the ceramic shell is broken with a hammer or other tools to bring out the beautiful bronze sculpture. Sprues are cut away and the sculpture is sand blasted. If the sculpture was done in parts, its individual parts are joined together. Metal chasing and sand blasting is done on the sculpture to create a fine finish and polish, and bring back the details that may be lost in the process.
Demolding Bronze Sculpture

Step 9 – Patination

A bronze sculpture undergoes patination if it needs to be given a different colour than its original golden. In patination, the bronze is exposed to chemicals that react with it and change its colour and/or texture. Colours such as brown, red, white, beige and silver can be obtained through patination. A protective coat is applied to the patina to give the colour longevity.

The process of creating a bronze sculpture is laborious and takes weeks. It needs high craftsmanship to create the original clay sculpture and handling of different materials for casting. Through this highly strenuous and painstaking work comes a single piece of bronze sculpture.
Bronze Sculpture Patination
AARNE has been creating exquisite bespoke bronze sculptures that speak of the beauty of high art. These premium sculptures add splendor to their surroundings, leaving us with a newfound appreciation of art. Our high-end bronze sculptures stay true for centuries, giving generations upon generations the pleasure of owning a unique sculpture nowhere else to be found. If you wish to own a premium handcrafted bronze sculpture for your residence or workplace, AARNE welcomes you to discuss your needs.

For more information about our bronze sculptures, please click here.

If you have any questions or queries, or if you are interested in getting a sculpture manufactured. Please contact us using the contact form on the ‘Contact Us‘ page. Or alternatively please email us at info@aarne.co.uk and we will get back to your enquiry as soon as possible.

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