How are bronze sculptures made?

Bronze casting is not as easy or straightforward to understand as one might hope. Behind every bronze sculpture lies a meticulous, multi-stage process that is steeped in both tradition and modern techniques. The traditional lost wax method, dating back thousands of years in places like Benin, Greece, Rome, and India, remains at the heart of bronze sculpture-making today, although it now benefits from contemporary tools and foundry environments.

Below, I’ll walk you through each stage of this intricate journey.

1. Mould making

The process begins by making a mould of the original sculpture, consisting of two-parts, or more parts for more complex forms.

• Flexible inner layer: a soft rubber is applied first, which captures fine textures and allows for easier removal due to its stretch.
• Rigid outer shell: then, a hard support jacket is built over the rubber, made from plaster, Jesmonite, or glass-fibre reinforced resin. This ensures the mould keeps its shape during the next steps.

Depending on the complexity of the form, multiple rubber and hard shell sections are used, with more divisions typically required in the rigid outer layers.

2. Wax casting

A hollow wax cast – about 5 mm thick – is made by brushing hot wax into the rubber parts of the mould in several layers. Once all sections are waxed and sufficiently hardened, they are reconstructed into a complete wax version of the sculpture.

At this stage:

• Hot tools are used to ‘touch up’ any seam lines or surface imperfections.
• The artist inspects the wax, may make small changes, and initials it with their signature and the edition number.
• Small sculptures may remain in one piece, but larger sculptures, like Family Group, are cut into sections to fit within the size limits of the furnace (Talos’s crucibles hold up to 40kg of molten bronze per pour).

3. Gating system: sprues and pouring cup

Wax rods known as sprues or runners are attached to guide molten bronze into the sculpture, and to allow air to escape:

• A pouring cup (shaped somewhat like a takeaway aluminium container) is added at the top to receive the molten metal.
• A riser is attached to let trapped air escape.
• Metal pins are inserted to hold the internal sections of the hollow sculpture and to support the next steps.

4. Shell formation (‘dipping’ or ‘Investment’)

The gated wax sculpture is repeatedly dipped into ceramic slurry and sprinkled with granular ceramic. Each layer is allowed to dry thoroughly, and the process is repeated several times to form a durable, heat-resistant shell around the wax.

To cast the sculpture hollow, a small hole or ‘window’ is cut into the wax and covered with wax paper. Later, the paper is removed, and a core mix (a different ceramic material) is poured into the sculpture . This then forms a slim interior cavity between exterior and interior ceramic walls, to be filled with the bronze liquid in the next stage of the process.

5. Wax removal (lost-wax)

Once the shell is fully dry, the entire piece is heated in a kiln. The wax melts out through the sprue system, leaving a hollow ceramic shell – an exact negative of the original sculpture.

6. Bronze melting and pouring

Bronze is melted in a furnace to around 1,000°C. The casting process is highly coordinated:

• Usually, three people are required: one to pour, one to support the crucible, and a third to skim off impurities just before the pour.
• Molten bronze is poured into the shell via the pouring cup, flowing down through the runners and filling the cavity as air escapes through the risers.

 

  

 

 

 

 

 

 

 

 

 

 

 

 

 

7. Cooling and shell removal (‘fettling’)

After pouring, the bronze-filled shells are laid in sand trays to cool and solidify.

Once cooled:

• The outer ceramic shell is carefully chipped away.
• Sprues, runners, risers, and metal pins are cut off and cleaned for recycling.
• The interior core mix is removed and the external surface is sandblasted.

8. Reassembly and ‘chasing’

Large sculptures – originally cast in separate sections – are welded back together using reference photos or the original sculpture to match form and texture.

Then comes chasing: a skilled process involving grinding, filing, and sanding the bronze to:

• Disguise welds
• Smooth seams
• Restore the artist’s texture and detailing

Chasing is an art in itself, requiring expert observation and a deep respect for the sculptor’s intent.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

9. Patination

Once assembled and cleaned, the sculpture is patinated:

• The bronze surface is heated (typically with a blowtorch) and treated with chemical solutions that react with the metal to create colours – ranging from earthy browns to greens, blues, or blacks.
• The artist is often invited to participate in this process, sometimes even bringing clients to choose colour tones.
• Patination is a highly skilled process, both on a technical and artistic level, usually performed by specialists equally knowledgeable about 2D (colours) and 3D (form). Patination is not just a finishing touch – it’s an important creative, artistic and emotional part of the sculpture’s final identity.

10. Sealing and finishing

To protect the patina:

• Wax or lacquer is applied to seal the surface.
• The wax is then buffed and burnished, creating a soft sheen and protective barrier.

Depending on whether the sculpture will live indoors or outdoors, different sealing methods are chosen to ensure its durability.

Are you looking to purchase a bronze sculpture?

Bronze casting is a sophisticated, layered process that marries ancient techniques with modern craftsmanship. Every stage – from mould-making to patination -requires precision, patience, and artistic sensibility.

If you’re looking to purchase a bronze sculpture or you’re exploring the idea, then please take a look at some of my work. I also offer a bespoke service, so if you would like to commission a bronze sculpture, please get in touch.