How It's Made: Bronze Sculpture
/One thing the Gallery is known for is its vast collection of bronzes, which includes works of all sizes and styles. In one visit, you’ll find everything from portly snoozing bears to cowboys charging on their horses to soldiers in the midst of battle. What all these sculptures have in common, however, is a single, frequently-asked question: “How do artists make bronzes?”
So in this blog post, we answer that question with an overview of the casting process. You’ll also see examples with a few available sculptures at the Gallery.
There are several methods of casting, including sand-casting, centrifugal casting, and the “lost-wax” method, which have been used for millennia. Discovered during the Bronze Age (3000 BC), these processes were first used in the manufacture of weapons and shields. But it didn’t take long before our artistic ancestors realized the material’s creative possibilities.
The most well known and widely used method of bronze casting is “lost-wax” casting, also known as investment casting or cire perdue. This technique will be our focus.
The Process
Sculptors begin with an original figure, typically made from clay or wax. Starting from clay adds steps to the process, but it allows the artist to make more editions later.
Starting from clay, the first step after the figure is complete is to make a mould consisting of a soft inner layer and hard outer shell. For the soft layer, the clay is coated in silicone, latex, or polyurethane rubber. After setting, this is covered in plaster or fiberglass, which hardens into a reusable mould. The original sculpture is removed. (In direct casting, not covered here, the clay becomes part of the finished bronze.)
Molten wax is then poured into the mould until it reaches the desired thickness.
Once the copy is removed from the mould, chasing begins. This is when artists use more wax to smooth rough edges and mend imperfections until it looks like the finished piece.
From here, wax spruing is added along with a funnel-like cup left open at the bottom where the metal will be poured. Sprues are ventilation tubes attached to various parts of the piece, which allow hot air to escape and ensure metal fills every groove without air bubbles. (Such issues in this step make metal-chasing much more laborious later.)
Next, the entire wax piece–spruing and all–is dipped in a slurry, first of silica and then a stucco-like mixture. This is repeated until the coating is a desired thickness. It’s then fired cup-down in a kiln, which hardens the coating into a ceramic-like shell. Any wax melts away, leaving negative space in the shape of the piece.
Once the shells are tested for leaks, they’re ready for the bronze. The shells are placed in a bed of sand, cup sides up, while still hot. They must remain hot for the pour, otherwise the temperature difference would shatter it.
The bronze is melted in what’s called a crucible in a furnace before being poured into the shells. From there, the pieces sit and cool before the shells are hammered or sand-blasted away to unveil the rough casting.
Next, metal-chasing is done on the bronze piece. Grinders and other power tools remove spruing, seams, and any imperfections, while any additional pieces of the sculpture are welded together. (Most larger, more complicated works are cast in multiple pieces.)
Lastly, many artists choose to add patina to their pieces. Sculptures and antiques develop patina over time, but sculptors can easily replicate an aged or burnished look. Unique hues can be achieved using chemical reactions combining various acids and sometimes applying heat.
Process Diagram
Diagram by T. Simpson and S. La Niece (Source: https://www.researchgate.net/figure/b-Indirect-lost-wax-casting-T-Simpson-and-S-La-Niece_fig21_276883645)
Process In Pictures
(Photos by YouFine Sculpture)
Bronze Sculptures At the Gallery
Doug Hyde (b. 1946) - “Contemporary and Traditional Designs”, Ed. of 10, bronze, 16 x 18 x 16 in.
Doug Hyde is known for his confident work in stone and his excellent bronzes. In his individual process, Doug first carves his pieces in stone and from there, he makes moulds for casting.
Felipe Castañeda (b. 1933) - “Mujer con Guitarra”, Ed. of 7, bronze, 23 ½ x 15 ½ x 20 ¾ in.
Known for his captivating depictions of the female form, Felipe works in marble, onyx, and bronze. His casting process follows the typical method, and his pieces commonly have a gray-blue patina.
Dan Ostermiller (b. 1956) - “Rearing Elephant” Monument, Ed. of 6, bronze, 147 x 69 x 46 ½ in.
An avid sculptor of animals–particularly monument-size works and water features–Dan Ostermiller works first in clay. The carved lines that texture his sculptures are indicators of the original material. Pieces this large are cast in multiple parts and welded together.
Glenna Goodacre (1939-2020) - “Tug of War”, Ed. of 35, bronze, 16 x 21 x 10 in.
In this iconic Glenna Goodacre piece, five children are engaged in a game of tug of war. (Fun fact: As a child, the Gallery’s director was a model for this sculpture. He is the boy furthest to the right.) Preferring clay, Glenna’s works display crisp detail and expression that is difficult to achieve in wax.
Michael Naranjo (b. 1944) - “Justice”, Ed. of 10, bronze, 33 ½ x 10 x 11 in.
As a sculptor who just happens to be blind, Michael Naranjo imbues his pieces with stunning energy and emotion. Michael’s works are easy to attribute due to their black patinas and faces without defined features. The smooth texture of the sculpture, seen in the folds of Lady Justice’s dress, indicates that the original was likely created with wax.
Ed Smida (b. 1961) - “Healing the Divide” (Homage to Ernest Blumenschein), Ed. of 9, bronze, 25 x 21 x 16 in.
Sculptor Ed Smida favors working in clay to create his bronze editions. His sculptures often include stylized figures made from thick pieces of clay. Such complex bronzes, especially those with multiple figures, would certainly be made in multiple parts and require substantial chasing to achieve the final look.
JK Inson (b. 1946) - “Old School”, Ed. of 10, bronze, 8 ¾ x 9 ¾ x 4 ½ in.
JK Inson is one of the few sculptors who executes every step of casting himself. Though he occasionally collaborates with foundries, he mostly works out of his home and studio. JK sculpts in oil-based clay (which he frequently makes himself to get the right consistency) and completes the rest of the process–pouring molten bronze, welding, and all–without any outside assistance.
“Old School” is a great example of a sculpture completed in one solid piece.
For pricing or more information on any of these pieces, please contact the Gallery at (505) 982-4631 or email inquiry@matteucci.com.