Copper Castings – Methodology

Copper ore has been mined and refined for thousands of years; there are estimates that it was first used in about 9000 B.C. Since then, copper has been made into weapons, drinking vessels and of course jewelry by many different ethnic groups in varied areas of the world.

Not only is copper a good conductor of heat and electricity, but it can also easily be worked and added to other various metals in order to form alloys such as bronze or brass for example.

The Bronze Age found copper being mixed with zinc or tin to make bronze or brass; the ancient Egyptians used the mixtures in casting statues. Bronze is harder then copper so those countries that developed the copper alloy became more powerful than their neighbors. Brass, the alloy of copper and zinc, became popular with first the Greeks, then the Romans.

Using heat was the most common process to reduce copper ore to pure copper ingots. Generally speaking, a hole would be dug about twelve inches deep, after which it would be lined with either rock or clay. The crushed copper ore would then be placed inside the hole and covered with a layer of charcoal, and then it would be set alight. In order to maintain the ideal temperature, oxygen was pumped from bellows.

At the end of the process, you would be left with a large lump of slag with the pure copper in the center. A special pottery vessel would then be used in order to refine the copper ore even further. This also made it easier to use the high grade copper for the purpose of copper castings.

One of the later methods was to let water run across the copper ore, which resulted in the high amount of copper. Iron is then added which evaporates, and the copper takes its place. Christopher Columbus had his ships hulls coated with copper to prevent corrosion and resist damage by marine pests.

The method of flash smelting which is used with ores that contain sulfur and copper, it is more environmentally safe then other methods. Developed in Finland, the ore is dried and powdered before being sprayed over a fluidized bed reactor and reduced to a molten state. The sulfur is reduced to a solid form which less toxic to the environment.

Today, the refinement of copper ore is done by electric furnaces and the ore is used for many applications. It conducts heat well so is used for wiring in homes and also in plumbing due to the resistance to corrosion. Copper and copper alloys are used in the casting of art objects as well as plating surfaces in hospitals that are touched often because the alloy is resistant to bacteria and germs.

Mark Smith is Manager of AA Alloy Foundry, a Copper Castings and Products Company situated in Johannesburg, South Africa. For more information on Copper Castings and Products, go to Copper Castings and Products
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