An important development of the Bronze Age was the evolution of metallurgy, which resulted in the discovery of bronze. Certain metals, notably tin, lead and (at a higher temperature) copper, can be recovered from their ores by simply heating the rocks in a fire or blast furnace, a process known as smelting. The first evidence of this extractive metallurgy dates to Serbian sites from the fifth and sixth millennia BCE.
In approximately the fourth millennium BCE in Sumer, India, and China, it was discovered that by combining copper and tin, a superior metal could be made, an alloy called bronze, representing the beginning of the Bronze Age. The discovery of bronze enabled people to create metal objects that were harder and more durable than previously possible. Bronze tools, weapons, armor, and building materials such as decorative tiles were more durable than their stone and copper predecessors.
Initially, bronze was made out of copper and arsenic, forming arsenic bronze, or from naturally or artificially mixed ores of copper and arsenic, with the earliest artifacts so far known coming from the Iranian plateau in the fifth millennium BCE. It was only later, approximately in 3500 BCE that tin was used, becoming the major non-copper ingredient of bronze. Tin bronze was superior to arsenic bronze in that the alloying process could be more easily controlled, and the resulting alloy was stronger and easier to cast. Furthermore, unlike arsenic, metallic tin and fumes from tin refining are not toxic. In the Bronze Age, two forms of bronze were commonly used. "Classic bronze," about ten percent tin, was used in casting. "Mild bronze," about six percent tin, was hammered from ingots to make sheets. Bladed weapons were mostly cast from classic bronze, while helmets and armor were hammered from mild bronze. The flag pictured below was also likely hammered from mild bronze.
Bronze flag (third millennium BCE)
Found in Shahdad, Kerman, (now Iran).
In many parts of the world large hoards of bronze artifacts have been discovered, suggesting that bronze also represented a store of value and an indicator of social status. In Europe large hoards of bronze tools, typically socketed axes with little to no signs of wear, have been found. Axes were the most valued tools of the period.
Socketed axe blades.
A hoard of axes from the Bronze Age found in modern Germany. Archaeological Museum of the state of Brandenburg.
Although bronze was originally used for producing weapons, metal workers soon applied the alloy to the production of art. Among the oldest and most common method of producing bronze sculptures is through the lost wax process, which creates hollow one-of-a-kind sculptures in whatever form the artist chooses. Dancing Girl (c. 2500 BCE), from Mohenjodaro in the Indus Valley, is perhaps the first bronze statue of the world. Although it is in a standing position, it was named Dancing Girl with an assumption of her profession. This is one of two bronze art works found at Mohenjodaro that show more flexible features when compared to other more formal poses. The girl is naked, wears a number of bangles and a necklace, stands in a naturalistic position with her right hand on her hip, and holds an object in her left hand, which rests against her thigh.
Dancing Girl (c. 2500 BCE)
Bronze. 4 1/8 in × 2 in. National Museum, New Delhi.
The Únětice culture arose at the beginning of the Central European Bronze Age (2300-1600 BCE). The culture is distinguished by its characteristic metal objects including ingot torques, flat axes, flat triangular daggers, bracelets with spiral-ends, disk- and paddle-headed pins and curl rings which are distributed over a wide area of Central Europe and beyond. An interesting mixed media object from this culture is the Nebra Sky Disk (c. 1600 BCE), which consists of a blue-green patina inlaid with gold symbols. These symbols have been interpreted generally as a sun or full moon, a lunar crescent, and stars (including a cluster interpreted as the Pleiades). Two golden arcs along the sides, marking the angle between the solstices, were added later. A final addition was another arc at the bottom surrounded with multiple strokes (of uncertain meaning, variously interpreted as a solar barge with numerous oars, as the Milky Way, or as a rainbow). Likely produced through a combination of hammering, the disk is possibly an astronomical instrument as well as an item of religious significance.
Nebra Sky Disk (c. 1600 BCE)
Bronze and gold. 30 cm diameter. Pergamon Museum, Berlin.