The following article is reprinted on November 29, 2005 with permission of the C. M. Russell Museum and is contained in Volume 2 issue 4, pp. 9-10 of Russell's West Quarterly, a publication of the C. M. Russell Museum. Individuals interested is learning about membership in the Museum may call (406) 727-8787 or visit their web site at www.cmrussell.org.
Caring for Bronze Sculpture
Once you have acquired a piece of bronze sculpture, how do you care for it? Although bronze is durable and will withstand a great range of atmospheric changes, it still can be damaged. Consideration goes into whether the intention is for natural aging of the surface or not. Even if the desire is for a naturally-aged patina, it may still be necessary sometimes to clean the surface.
Dusting periodically with a dry, soft cloth or brush reduces build-up. You can use the brush attachment of your vacuum cleaner, as long as the sculpture does not have any loose pieces that might be pulled away. If a bronze is very dirty or grimy, with caked-on residue (sometimes the case with outdoor sculpture or a piece that has been in storage), it can be carefully cleaned with a solution of a mild dishwashing detergent (soap will leave a residue; any cleaner containing abrasives will damage the surface, as will harsh chemicals) and distilled water.
Test a less obtrusive area first, using a cotton swab (to make sure none of the surface patina is removed). Let it dry thoroughly and check the surface. Continue cleaning the entire surface, using swabs and cotton pads (discard when they become saturated with grime -- you do not want to redeposit it). After cleaning is completed, rinse thoroughly by going over the surface with distilled water on a cotton pad to be sure all of the detergent is removed. If the sculpture is an outdoor installation, you can use a hose and a gentle spray to rinse.
Dry the piece completely, making certain no moisture remains in crevices -- a hair dryer set on low is an excellent tool. As this cleaning will have removed any protective wax, you may want to reapply some to an indoor sculpture. An outdoor piece will definitely need protection. Suggested waxes include Renaissance Wax (a pure microcrystalline wax that will not yellow, available at some art supply stores or online) and Johnson's Paste Wax. There are others, but be sure not to use one that contains any cleaning agent. Apply a very thin coat with a soft clean cotton cloth, being sure to cover the entire surface. (Using too much wax does not harm the bronze, but it will accumulate in the crevices and be difficult to remove.) Allow the wax to dry for several hours, out of the sun or strong light (outdoors, do this in a shaded area, or in the late afternoon after the sun is no longer bright). When the wax is dry, buff the bronze by hand, using another clean, soft cotton cloth. More coats of wax may be added, if a shinier effect is desired. Additional coats will not harm the bronze. In a highly humid climate, or an environment with a higher degree of air pollution -- a large city, or a location near industry -- you may wish to clean and wax more frequently. Observation of the surface of the bronze will be your best guide.
Collector's Questions: I have a bronze sculpture. How was it made? Do I have to do anything special to take care of it?
Objects made of bronze have been around for at least 6,000 years. An alloy composed primarily of copper and tin, bronze is an excellent medium for cast sculpture. It melts easily, but hardens to a durable finish. Around 4,000 years ago, Mesopotamian artisans were able to move beyond making tiny solid bronze pieces, devising a method that is still in use today. Called the lost wax method, it makes possible the creation of larger, more complex bronzes that are a thin shell of metal with a hollow interior.
A bronze sculpture is created in many steps. The artist first creates a model, which can be made from various materials such as clay. A master mold is made of the model by covering it in a durable material such as plaster. The mold is carefully cut into pieces and removed from around the model (which remains intact). If only a single casting is to be made, this mold is used for the bronze casting. If there is to be an edition of more than one piece the master mold can be used more than once. Wax is layered into the inside of the mold, producing a duplicate of the original model when the mold pieces are removed. The artist can make last minute changes or alterations at this stage. When the artist is satisfied with the wax model, it is then encased in plaster or ceramic mold material, vents and pour holes are added, and the molten bronze is poured into the mold. The hot metal melts and replaces the wax, which is then "lost" out of the mold. When the piece cools, the mold is broken away to expose the bronze sculpture. Because the master mold still exists, the artist can continue to make wax models and cast more bronzes.
Because the artist makes each wax model and oversees the casting, each bronze that results is considered original. The concept of limited edition is fairly new. The earliest multiples cast in the first American foundries in the late 19th and early 20th centuries, such as Roman Bronze Works in New York, were cast as orders came in; there was no predetermined number that would be cast. Artists such as Russell, whose first bronze, Smoking Up, was cast in 1903, sold works through retail outlets -- in Russell's case, Tiffany's in New York. A buyer would see an example, order it, and the piece would be cast. There are sometimes numbers on these casts, used by the foundries to record the pieces.
By the middle of the 20th century, artists and foundries began to create limited editions, determining in advance how many pieces would be cast. Editions are marked with the individual piece number and the complete number; for example, if the edition includes 50, the first one cast is 1/50 and the last one cast is 50/50.
After a piece is cast, it can be polished, creating a warm, rich surface that will eventually age (oxidize) to a natural, verdigris patina. The artist, though, can create a different type of variously-colored patina, applying chemicals to the surface of the bronze and exposing it to heat. A final polishing may be done to further enhance the beauty of the bronze.
Editor's note: RL readers may also enjoy TFAO's other Conservation resources.
Read more articles and essays concerning this institutional source by visiting the sub-index page for the C. M. Russell Museum in Resource Library.
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