Materials in Today's World

Why Did it Take So Long Between the Bronze Age and the Iron Age?


The beginning of the Bronze Age occurred around 3500 BCE and the beginning of the Iron Age began around 1000 BCE. Why did it take 2000 years for bronze to be replaced by iron? Looking around us we see structural steel and concrete seemingly everywhere in our modern cities. However, the processing of iron is not a trivial process.

Due to limitations in furnace designs, i.e., the maximum obtainable temperatures, the availability and quality of iron varied greatly. As we’ll see in the next lesson’s video, Secrets of the Viking Sword, throughout history there have been legendary quality swords, i.e., Damascus and Samurai to name just a couple. These swords were produced using time-intensive and, many times, ritualistic processes. These blades were produced in areas known in the modern day as Iran, Japan, and China. Most of the iron used in weapons during the Iron Age, i.e., Roman swords, was a low-density iron sponge-like material. This sponge-like iron was then pounded to shape, densify, and remove impurities. Bronze was superior to the iron produced commonly, so why did iron ultimately replace bronze?

Bronze weapons were indeed of higher quality than the common iron weapons typically produced. However, tin, which is required for the production of bronze, is not abundantly available. As a consequence, bronze weapons were the weapons utilized by nobles, royalty, pharaohs, etc. The common foot soldier was not going to possess bronze weapons; there were not enough to go around.

Unlike tin, iron ore is readily available. So, although inferior to bronze, an army of hundreds or thousands could be equipped with iron weapons, which was not practical with bronze weapons. So, the ability to produce large numbers of iron weapons overcame the advantages of bronze. Eventually, time and further development allowed for the production of these so-called legendary swords which supplanted bronze as the weapon material of choice for the nobility. But it wasn’t until much later, during the advent of the Industrial Revolution, that advancements in furnace design and process control enabled the reliable and massive production of the iron alloy known as steel. In this lesson’s video, the importance of steel and how the production of steel was changed during the beginning of the Industrial Revolution will be showcased. We will return to this topic at the beginning of the next lesson on metal alloys.

Now, let’s take a step back from our discussion on the historical development of metal processing and begin an introduction to the structure of metals.