How Bronze Sculpture is Made

A step-by-step look at casting a piece of bronze sculpture

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Just how "original" is a piece of bronze sculpture? By observing the process of creating such a piece, either one-of-a-kind or one in a limited-edition series, it becomes clear that each is unique.

Dating back centuries, the lost-wax method of casting is used by New Mexico's world-renowned foundries to realize bronze sculpture in a wide variety of images from Indian and western to impressionistic or abstract.

The process begins with the artist's original piece sculpted in clay, wax, wood or other material.

Mold

Figure 1
Rubber mold pulled from original

The "embedded mold" method begins with the original sculpture being halfway embedded in soft water clay. Silicone rubber is meticulously painted on the exposed half; then a plaster shell is fashioned over the hardened rubber. The piece is turned over, the clay removed, and the second exposed half is painted with the synthetic rubber and covered with a plaster shell. This method produces a rubber mold in two easily-separated halves which can be pulled away from the artist's original without causing damage. The completed rubber mold, a "negative" version of the artist's "positive" original, becomes the new master from which all copies in an edition are made.

The next step creates the second "positive" in the process: a wax duplicate of the artist's original. First, the interior of the rubber mold is painted with molten wax; the halves of the mold are then put together and the hot, liquid wax is "slushed" into the mold. The wax cools from the outside inward. When it cools and hardens to a thickness of 3/16" to 1/4", the excess wax is poured out. The rubber mold can then be opened and the wax duplicate removed. (The mold is then carefully stored in preparation for repetition of this process for each piece in the edition. When the final bronze in an edition is complete, the rubber mold is destroyed.)

At this point, the artist usually returns to inspect and correct the wax model. Hours, and perhaps days, of painstaking dressing (correcting) the wax assure faithful reproduction of the original. A unique edition number is incised into the wax at this stage (e.g. 2/10 means that this piece is the second casting in a total edition of ten.)

Next, a wax funnel is added to provide an entrance for the molten metal. A series of wax channels, or sprues is attached to provide a path for the liquid metal, and for air to escape, assuring an even flow of metal to all parts of the mold during the pouring (Figures 4, 5).

The next step in the process resembles battering and breading a piece of chicken! The sprued wax Figure is dipped into a viscous ceramic solution. It is then rolled or dipped in fine sand which gives detail, and then in a coarser sand which gives strength. This is repeated until the layers produce a strong ceramic mold about 1/4 inch thick-creating the second "negative" in the process.

Once hardened, the ceramic mold is heated to 1500 degrees F and "burn out" occurs. It is here that the wax is "lost" — in French, cire perdue — and, in the process, the mold is strengthened.

Sprues/channels

Figure 2
Placing sprues or channels

Pouring bronze

Figure 3
Pouring bronze

Molten bronze, an alloy of copper, silicone and manganese, is poured into the mold. After the bronze has cooled and solidified, the mold is broken open, discarded, and the casting--the final "positive"--is removed. Refining this raw piece is a delicate and demanding process that includes removing rods of bronze formed from the sprues, recreating the surface texture in these areas, and sandblasting remnants of the ceramic mold from the piece. In the case of a monumental sculpture or any sculpture cast in more than one piece, the sections are assembled at this time.

Now the patina, or surface coloring, can be applied. Years of experience, hours of labor, a variety of chemicals, and the help of high temperatures hasten what is actually a natural process, yielding subtle to dramatic coloration.

Vignir Johannsson's "Against the Wind" is now complete. A certificate is prepared to document the exact size and weight of the piece, identifying it as the "original" sculpture it is, with no other in the edition exactly like it. This documentation acts as a safeguard against fraudulent practices such as surmoulage, an unauthorized casting taken from a bronze sculpture rather than from the artist's original.

V. Johannsson's sculpture

Figure 4
Vignir Johnannsson
"Against the Wind"    27.5" H


By Pamela Michaelis, founder of The Collector's Guide and former host of “Gallery News” radio show on KHFM 95.5 remote, classical radio in Albuquerque.

Photography by Vignir Johannsson taken at Shidoni Foundry remote Tesuque, NM, during the creation of his piece entitled "Against the Wind."

Originally appeared in
The Collector’s Guide to Santa Fe, Taos and Albuquerque - Volume 14


Related Pages

Alternative Scupture Media article
Touching Beauty - Michael A Naranjo
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Glossary of Bronze Sculpture Terms article


Collector’s Resources

Albuquerque

The Albuquerque Museum of Art & History | 505-243-7255
Barbara Burzillo rem By appointment | 505-228-3199
Concetta D Gallery | 505-243-5066
Weems Galleries pic Louisana Plaza and Plaza Don Luis | 505-293-6133
Tomi LaPierre Studio rem By Appointment Only | 575-523-7479
The Adobe Fine Art | 575-257-5795

Santa Fe

Alexandra Stevens Gallery | 505-988-1311
Altermann Galleries & Auctioneers rem 345 Camino Del Monte Sol | 505-983-1590
Patricia Carlisle Fine Art rem 554 Canyon Road | 505-820-0596
Chimayo Trading and Mercantile | 505-351-4566
Galerie Zuger | 505-984-5099
Glenn Green Galleries rem 136 Tesuque Village Road (CR 73), Tesuque, NM | 505-820-0008
Mark Yale Harris rem Represented by Reflection Gallery | 505-995-9795
Allan Houser Gallery & Sculpture Gardens | 505-471-1528
The Frank Howell Gallery | 505-984-1074
Manitou Galleries | 505-986-0440
McLarry Fine Art | 505-988-1161
Meyer Gallery | 505-983-1434
Michael Henington Fine Art Gallery rem 416 Agua Fria | 505-474-0791
Nedra Matteucci Galleries | 505-982-4631
Niman Fine Art pic 125 Lincoln Ave - Suite 116 | 505-988-5091
Oviedo Carvings & Bronze | 505-351-2280
Peyton Wright Gallery | 505-989-9888
Reflection Gallery | 505-995-9795
Tom Ross Gallery | 505-984-8434
Sage Creek Gallery | 505-988-3444
Shidoni Galleries / Sculpture Garden / Foundry | 505-988-8001
Ventana Fine Art | 505-983-8815
Susanne Vertel pic 1500 Wilderness Gate Road | 505-988-5516
Joe Wade Fine Art | 505-988-2727
Wadle Galleries Ltd pic 128 West Palace Ave | 505-983-9219
Windsor Betts Art Brokerage House rem 136 Grant Avenue | 505-820-1234
Zaplin Lampert Gallery | 505-982-6100

Taos

Total Arts Gallery | 575-758-4667
Walden Fine Art pic 125 Kit Carson | 575-758-4575

RESOURCE LISTS UPDATED WHEN VIEWED | ARTICLE CONTENT REVISED October 14, 2009

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