The bitterness of poor quality remains long after the sweetness of low price is forgotten! – Benjamin Franklin
Signs of a Quality Bronze Sculpture
When considering purchasing a bronze sculpture what do you need to know? Is the sculpture a high-quality casting? Is it a high quality original or a low-quality reproduction? Is it even really a bronze sculpture? These questions become very important if the piece is considered either an antique or a piece by a well-known artist.
Is It Really Bronze?
Is the sculpture really made from bronze? True bronze is an alloy of copper and tin. However, many modern bronzes are made from a silicon bronze alloy which uses little to no tin and a certain amount of silicon. It is well regarded as a sculpture casting medium and provides for high accuracy in casting.
Not all bronze alloys are made equal in quality. Some antique and inferior quality bronze alloys have higher tin content or incorporate dangerous additions such as lead, arsenic, and manganese.
It may not even be bronze…
Recognizing Bronze
Bronze clear of any patina or paint has a color that ranges from golden to a rose gold hue. Antique bronze will tend to have more of a rosy color due to a higher copper content.
Some false bronzes include: Cold cast resin bronzes, spelter, and brass.
Cold Cast resin bronzes are made from resin with bronze dust mixed into the resin. They are mostly resin and so are much lighter than bronze, but they are occasionally weighed down in the bases. If the base feels heavier than the bronze it is probably resin.
Spelter is a zinc-lead or zinc-aluminum alloy that was developed in the 1500s.It can be patinated or painted to look like bronze. Spelter is a lighter and softer metal than bronze. If you examine a scratch in a spelter piece it will look more of a white or silver color than the gold or rose gold of a true bronze. Spelter in antiques is more common in pieces dating from the 1860s or during World War I due to bronze shortages. It was also very popular during the Art Deco period.
Brass is another copper-based alloy. It typically is a mixture of copper and zinc. Brass will have the closest color to a true bronze because it does include copper. However, the zinc will give it a lighter color than true bronze and the finished metal will be harder than bronze but also more brittle. Bronze is more likely to dent or bend while brass will break or crack.
Evidence of a Quality Casting
Looking at a bronze sculpture there are several areas to examine to recognize a high-quality bronze casting.
The first area to examine is the fidelity of the casting.
Details
How accurate is it? If you have images of the original clay or a known original casting, compare the casting to that original. How close do the faces, fingers, and feet match the original? Research the original pieces. Were originals mounted on bases? Frederic Remington is one sculptor whose popularity has led to many reproductions being made. However, his original pieces were never mounted on bases.[1] Compare signatures. Examine for foundry marks and edition numbers.
Compare the size
Bronze shrinks as it cools between 2-3% in size. If you know the size of the original and the piece in question is smaller, then it is likely that the piece was molded from an original and is a reproduction.
Also, if you do your research and the artist worked within a specific size range and the piece in question is a known piece but the size is different it is probably a reproduction.
Process Quality
Making a bronze sculpture requires skilled labor in a variety of areas. The lost wax process involves molding, wax casting, investment, metal casting, metal working, and patination. We could look at each aspect and find areas that indicate a lower quality piece. However, today we will focus on the bronze casting and metal finishing aspects.
Voids or holes in a bronze casting can be an indication of defects in the casting caused by trapped gas or shrinkage. These holes should be filled during the metal finishing stage. Irregular metallic crusts that appear on the surface that are a different color could indicate dross or slag inclusion which means the metal was not skimmed for impurities enough before pouring.
Metal working defects can range from unfinished or shallow welds, mismatched seams, and improper chasing. Unfinished welds leave holes or cracks that can allow moisture to gather inside the sculpture. This can be especially damaging to outdoor installations as the moisture can then freeze inside the sculpture creating larger cracks in the sculpture.
Shallow welds result in uneven thickness of the metal leaving weaker spots in the structure of the piece. Shallow welds can also cause uneven application of the patina due to non-uniform heating of the metal. Mismatched seams or unfinished texturing at weld points lead to an unfinished look to the sculpture and visually obvious seam marks in the sculpture. Chasing is the process by which the seams of a piece are aligned before welding. Improper chasing can result in bulges or divots at the seams of the sculpture. This can cause the piece to look damaged or unfinished.
[1] https://fredericremington.org/sculptures-c32.php#:~:text=If%20your%20sculpture%20is%20secured,a%20sign%20of%20a%20reproduction.