Some Interesting Historical and Metallurgical Facts About Copper by David Smith

Making copper weathervanes is like alchemy, in that there is a division of the work into practical effort and visionary reward. George Washington, Paul Revere and Thomas Jefferson were, among other things, outstanding coppersmiths. Washington made for his Mount Vernon home a famous weathervane he called "Dove of Peace." Paul Revere, a coppersmith par excellence, made many weathervanes and the world's largest copper company today--Revere Copper--is still owned by his family. (All sheet copper I use in my work has a purity of 99.999%, and is made by Revere Copper Company.) Revere also fabricated a bronze (an alloy of copper) cannon for the USS Constitution. Thomas Jefferson, being the brilliant artist, innovator, and inventor that he was, took the weathervane a step further: he made a copper weathervane for his Monticello home that featured an indoor indicator arrow that he could view from his living room.
There are no books on how to make copper weathervanes nor are there any standard tools. My only tools consist of an 8- and 16-ounce ball-pein hammer, an oak stump on which I hammer my work, duckbill shears for cutting sheet copper, a propane torch and silver alloy solder. Occasionally I'll look for a "found object"--a piece of metal with a unique form--for making certain textures. That's all there is to it. In all my weathervane designs I adhere to the form follows function principle associated with modern architecture and industrial design in the 20th century. The principle is that the shape of a building or object should be primarily based upon its intended function or purpose.

Form follows function: Detail of a grotesque weathervane by David J. Smith. (2002)
Private residence, Sandwich, Massachusetts.

Some interesting facts about copper:

Copper has very powerful anti-microbial properties. For example, a stainless steel sink will contain germs for two weeks while a copper sink will be germ-free in two hours. This was confirmed by a recent EPA study and is why most hospital door knobs, handrails, etc., are made of copper or plated with brass (a copper alloy).

Copper often is referred to by economists as "The Ph.D Economist." It's used in everything from wiring to pipes and any fluctuation in its demand is a good indicator of the health of the economy.

Copper is man's oldest metal. Its use dates back 10,000 years to the ancient Egyptians and a copper pendant found in what is now northern Iraq dates back to 8,700 BC.

Copper is an element. Its symbol in The Periodic Table of Elements is "Cu." Copper is in the family of "heavy metal" elements which also includes cobalt, manganese, molybdenum, vanadium, strontium, zinc, mercury, lead and cadmium. For artistic purposes copper is a wonderfully malleable metal and has a melting point of approximately 2,000 F. Unlike steel which hardens upon cooling, copper retains its softness. Repeatedly hammering copper will cause it to become progressively brittle (called work hardening); heating it (called annealing) will return it to its original softness.

Copper in its pure state is rarely found in nature, but is usually combined with other chemicals in the form of copper ores. There are about 15 copper ores mined commercially in 40 countries around the world. The most common are known as sulfide ores in which the copper is chemically bonded with sulfur. Others are known as oxide ores, carbonate ores, or mixed ores depending on the chemicals present. Many copper ores also contain significant quantities of gold, silver, nickel, and other valuable metals. Semi-precious copper-based minerals such as azurite and malachite are prized by collectors for their strikingly beautiful colors. Turquoise--my birthstone--is an opaque, blue-to-green mineral that is a hydrous phosphate of copper. It is rare and valuable in finer grades and has been prized as a gem and ornamental stone for thousands of years owing to its unique hue.

Copper is 100% recyclable without any loss of quality whether in a raw state or contained in a manufactured product. Copper is the third most recycled metal after iron and aluminum. It is estimated that 80% of the copper ever mined is still in use today.

Copper is a component in many alloys. For example, bronze is an alloy made by combining copper and tin; brass is a copper alloy with many commercial applications and is made by combining copper and zinc as well as other metals such as nickel and aluminum. There are dozens of copper alloys, each having its own unique metallurgical properties such as melting point, tensile strength, conductivity and corrosion resistance. "Admiralty brass" contains 30% zinc, and 1% tin which inhibits dezincification in many corrosive environments and is used in the ship-building industry, along with its cousin "naval brass," which is 40% zinc and 1% tin. "Alpha brasses" with less than 35% zinc, are malleable, can be worked cold, and are used in pressing, forging, or similar applications. "Beta brasses" with 45-50% zinc content, can only be worked hot, and are harder, stronger, and suitable for casting. Manganese brass is a brass most notably used in making golden dollar coins in the United States. It contains roughly 70% copper, 29% zinc, and 1.3% manganese. Muntz metal is about 60% copper, 40% zinc and a trace of iron, and is used as a lining on ships. Nickel brass is composed of 70% copper, 24.5% zinc and 5.5% nickel used to make pound coins in the pound sterling currency.

Copper oxidizes to a characteristic green or bluish-green color. This green patina that forms naturally on copper and its alloys (bronze and brass), sometimes called verdigris or noble rust, usually consists of a mixture of chlorides, sulphides and carbonates (copper carbonate, copper chloride or copper sulphide). A copper or bronze work of art can take a minimum of 30 years to develop a verdigris patina; cleaning an antique of its patina can diminish its value by up to 85%. For artistic purposes a patina on copper, bronze or brass can be created with the use of chemicals such as liver of sulfur, sodium thiosulfate, ferric chloride, ferric nitrate, cupric nitrate, cupric sulfate, and ammonium chloride among others. These chemicals are applied either in cold or hot solution--depending on the formula--and can yield colors ranging from dark bronze to green, blue, bluish-green, or straw yellow.
--David J. Smith
Sugar Land, Texas