Archeologists use the term "Iron Age" to describe a stage in the technological development of human cultures, not a specific time period. Iron Age cultures used iron extensively for tools and weapons, rather than relying on earlier technologies such as stone or bronze. The Iron Age began and ended at different times in the histories of Europe, China, Africa and Central Asia.
Discovery of Iron
Metalworkers used bronze for many centuries before the discovery of iron, creating bronze weapons, agricultural tools and ornaments. Ancient smiths knew how to melt copper and tin, remove any impurities, combine them into a bronze alloy and cast the desired implement using a mould. Iron melts at temperatures higher than ancient smiths could create, so they couldn't use the same method to make iron implements. According to "The European Iron Age" by John Collis, ancient smiths must have been experimenting with new techniques for a long time before discovering the secrets of forging iron.
To make a useful iron tool such as a blade, a smith would take lumps of iron ore and heat it in a furnace mixed with charcoal, creating a large chunk of iron called a "bloom." To remove impurities, the smith had to hammer the bloom into the desired shape on a forge, producing a wrought iron tool or ornament. Wrought iron tools are harder than bronze tools, but they also require much more work. In the early Iron Age, bronze was still used for most tools and weapons and iron was largely a prestige item rather than a practical option for most people. In the early European Iron Age, some warriors were buried with especially long iron swords, as if to display their elite status.
Earlier smiths only knew how to make wrought iron, but later smiths discovered that they could create steel by quenching the hot iron and reheating it repeatedly. Heating the iron in the charcoal over and over caused the iron to absorb enough carbon to transform into steel. Steel blades are harder than either bronze or wrought iron and they can take and hold a better edge. Early steel tools and weapons didn't contain enough carbon to become steel all the way through, so even though the edge was hard, the center of the blade was still too soft. Smiths solved this problem by developing increasingly sophisticated methods of combining hard and soft layers to produce highly effective steel weapons and tools.
The Iron Revolution
Because iron-working was so complex, it took centuries to perfect the technology. However, once iron tools and weapons started to become widely available, they revolutionized ancient life. Iron ore is much more common and widely available than copper and tin, so communities could make their own tools and weapons without having to import the necessary raw materials. Iron plows had heavier blades capable of getting to the more fertile layers of soil at the bottoms of valleys, enabling Iron Age farmers to produce more crops with less work. Farmers using iron scythes could cut more hay, allowing them to keep larger herds of animals. Warriors using iron swords had a military advantage, because iron swords could be made harder and longer than bronze weapons. After the widespread adoption of iron technology, trade increased and society rapidly became more complex, wealthier and more stratified.
- European Prehistory - A Survey; Sarunas Milisauskas
- The European Iron Age; John Collis
- Chinese Studies in the History and Philosophy of Science and Technology Volume 179; Fan Dainian and Robert S. Cohen
- Nigeria's Diverse Peoples - A Reference Sourcebook; April A. Gordon
- History of Civilizations of Central Asia, Volume 1; Ahmad Hasan Dani, Vadim Mikhaĭlovich Masson
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