Bronze is a metal alloy produced by blending copper and tin in various amounts, depending on the application. Additional elements such as manganese, lead, and phosphorous are added to create bronze with specific properties. Bronze is found in bells, statuary, bearings, gears, valves, pipes, and other plumbing fittings, and it is a sturdy, durable metal when well cared for. Humans have been working with bronze for over 3,000 years in various parts of the world, using it for weapons, coins, tableware, and an assortment of other household purposes.
Bronze is made by smelting copper and tin together. When bronze is cast for use in statues, it contains between two and 20% tin, while bells use a higher percentage of tin: 15-20%. Additives are included when the bronze needs to be more workable, harder, or easier to cast. For example, phosphorous is added to harden bronze for use in tubing and various machine parts, while lead is included to make bronze take more readily to casting. Bronze is often confused with brass, an alloy of copper and zinc, but the two alloys have different properties and are used for different things. In addition, bronze is much harder than brass.
Bronze has several properties that make it valuable in industrial applications. The first is that the metal causes minimal friction, making it highly useful for machine parts and other applications that involve metal on metal contact, such as gears. Bronze is also non-sparking, so it is often used to make tools for use in combustible environments. The resonance of bronze also makes it ideal for use in casting bells.
One of the more unique properties of bronze is the natural patina that forms on it, turning the bronze a dark, dull color. This patina is actively encouraged with most bronze, because it provides a protective layer, preventing oxidation below the surface of the bronze. Before being shipped, most bronze is coated with a thin layer of lacquer to protect the metal and the patina, making the metal very easy to care for.
Bronze looks its best when it is minimally treated. The metal should be kept very clean with a soft cloth, and can be waxed every couple of years to renew the patina, but it should not be heavily polished or scrubbed, and abrasives should never be used on bronze. If the bronze becomes very dirty, it can be gently brushed or washed with a solution of one tablespoon of salt to three quarts of boiling water, as long as the bronze is rinsed clean and dried afterwards. Rarely, bronze will be attacked by “bronze disease,” a type of corrosion that eats into the bronze. If a bronze piece starts to corrode, it can be washed in multiple changes of boiling distilled water, or professionally treated.
What's it worth? Take a look at this Bronze price guide: sold listings for a value indication.