6 Metal Sculpture Materials and How to Determine the Difference Between Them

There are a number of circumstances when a metal sculpture owner may need to determine exactly what material a piece is made of. Perhaps they need to write a description of the item to sell or insure. In other cases a piece has been damaged and when inquiring about getting it repaired the restorer/conservator needs to know the material in order to give a quick estimate.

In any case, people often assume metal sculptures are bronze which is not a bad guess since it is the most often used material for cast metal sculpture. But cast metal sculpture can also be poured from iron, zinc, lead, gold or silver. There are several indicators that can lead to a conclusion of which metal you have.

First of all look at the surface of the piece. If it has been exposed to the weather without proper finishing and waxing then the piece may show corrosion. Corrosion will have a different appearance on different metals. Secondly, if a part is broken from the sculpture this is an opportunity to look at the raw unfinished material which can be very helpful. There are a couple other tips for different metals which I will discuss under each topic.

BRONZE. Most of the older European bronzes were poured in what is called a "red brass" which is 85% copper, 5% tin, 5% lead and 5% zinc. This combination of metals was used to improve the performance of the metal during the pouring, finishing and patination process. A corroded bronze sculpture will have a light greenish cast and possibly a patchwork of irregular black and green areas.

At a break, the metal will have a slightly reddish, golden quality to it. When you try to scratch the inner part with a sharp object it may leave a slight scratch but will be somewhat hard and will not leave a burr on the edges of the cut.

ZINC. A very common metal for the less expensive sculptures but can still be highly prized. The casting process requires a reduction in heat as the melting temperature is lower. Zinc is a metallic element and is normally a gray silver color. Corrosion on zinc will be white. Many of the fine zinc pieces are copper plated then patinated and sealed. Over time, both the patina and plating can become worn and disappear all together.

The color of the metal at the break will be very bright and have a large crystalline structure. Some of the facets of the structures will be extremely shiny especially if it is a new break. The inner surface of the break is soft and can be easily scratched and you will feel a raised burr at the edge.

GOLD. Very few sculptures are made from pure gold with the exception of many Egyptian and pre-Columbian pieces. A more widespread use of gold is to plate bronze sculpture with a coating of gold. Gold does not tarnish with time but if not kept clean it can look discolored from dust and grime.

SILVER. There are a few sculptures out there made with pure silver but a more common use is to plate bronze or zinc sculpture. Just like silver jewelry or tableware it will tarnish to black when not kept polished.

CAST IRON. Place a small magnet near the surface of your piece. If it attracts then your piece is probably cast iron.

LEAD. There are a few sculptures made from pure lead. They are extremely heavy and corrosion will be white.

Source : Ezinearticles