One hears about the iron age and the bronze age—eras in which people discovered metallurgy. But how did that happen? Was it like:
1. Look at rock
2. See shiny
3. Try to melt the shiny out of the rock
4. Profit?
Explain it to me!
In: 1643
I’m no expert, but I’m into this topic. So keep in mind, I’m not very well-sourced in my statements, just giving a general accumulation of knowledge that may or may not be entirely accurate.
First thing to know is, mankind has pretty much always been messing around with rocks. We have records of alchemy being practiced in ancient Greece, China, India, and Egypt, where they tinkered with different plants, minerals, and other materials in all sorts of ways. Some of the records we’ve found suggest that cultures have been doing this as far back as 10,000 BCE, with the implication that the practice went back even earlier than that, and we just don’t have the written records that we can read to confirm it. At some point, as has been said, we’re pretty confident that we started messing with rocks before we figured out writing. So it’s pretty hard to know exactly when it started.
But before we got to metals, we were making tools out of stone. We figured out that, while stones are really hard, they can be broken down. In some areas, people ground the stones against each other, filing away bits from the outer surface of both rocks, until they formed a rough shape that could be used. But the lucky places had minerals like flint and obsidian: those could be broken, chipping away big shards from the rocks. This is good for tools, because it could create really sharp edges that were awesome at cutting. And with some practice, you could control the angle that you broke bits off from, and shape the flint into specific tools.
Our first records of metallurgy (that is, extracting and shaping metal from rocks) go back to the 9th millenia BCE in the general area of the Middle East. We’ve found shaped metal objects, primarily tools, that we dated to get that origin time. Probably the first metal to be worked in this way was lead, with copper, silver, gold, tin, and eventually iron following behind.
One of the processes used in metallurgy is smelting, or melting the rocks until the metals can be separated from the rest of the stone they’re found in. This was likely figured out by accident, because lead and tin actually melt at temperatures that could be reached by a regular campfire. We figured out that, if we separate the metals from the rocks and throw the rocks away, the metals left behind are much stronger and easier to work with. From there we figured out casting (melting the metal, and pouring it into a shaped container, so that the metal cools into that shape), and forging (shaping the metal with tools, often while it’s hot and more flexible).
Lead and tin are dense, but not very hard (lead being more so). So they weren’t very good as weapon or tool materials. But lead bullets, which could be fired from slings, have been found. Metals like silver, gold, and tin, being relatively soft, were often used for ornamental items, like jewelry, cups, and other objects that weren’t expected to take a lot of force in their use.
Copper was slightly harder to work out, because it melts at a higher temperature than those metals. The current theories are that ancient peoples used something like a pottery kiln, which was also in use around the time, and which could produce hotter temperatures. But before we figured that out, we were already working copper cold (that is, just beating it into shape with no heat added). Because copper is pretty soft, as far as metals go, it can be worked in that way. But despite being that malleable, it can still be worked into weapons and tools with sharp edges. Thus, we got copper weapons that worked better than stone ones. And it was such a big deal, we named a whole age after it.
Bronze was the next big development, around 4,200 BCE. Someone combined tin (or arsenic) and copper (in what might have been a chocolate/peanut butter kind of accident), and discovered alloys: combinations of minerals and metals. The resulting alloy, bronze, was still workable with the technology mankind had figured out at the time, but when cooled it was much harder than copper. So we turned it into the main material for weapons, armor, and tools. And it was such a big deal, we named a whole age after it.
Then there was iron. Iron is a lot harder than any of those metals, and it needed to be heated to even higher temperatures to work with, so it took longer for us to get to that. But we have examples of worked iron from as far back as Ancient Egypt. The theory was that, instead of getting impure iron from the ground, the earliest iron items we found were made from meteoric iron: large chunks of relatively pure iron that came from space. Meteors were also easy to reach, since they land on the Earth’s surface, compared to digging large veins of iron from the ground. But because there was only so much workable iron available, it wasn’t put into common use by anybody yet.
The process for smelting iron ores was eventually figured out around 1,200 BCE. It’s credited to the Hittites of the Middle East, but was likely figured out by other peoples separately as well. Things like charcoal (which reached higher temperatures than regular wood), and bellows (which blew air into the fire and made it burn hotter for a time) were used to help this process. The process involved constructing bigger and badder furnaces, such as bloomeries, which created controlled temperatures that could separate the iron from most of the rock, but wasn’t hot enough to actually melt the iron. The iron “bloom” then had to be reheated and folded over and over, to separate the slag and impurities from the metal.
But true iron-working was figured out in the 5th century BCE in the area of China. They built furnaces that were finally hot enough to melt iron, and thus the metal could be cast and worked. The resulting metal was *pig iron*, which had a lot of carbon in it, and other impurities like silica. While it was hard, it was also quite brittle. Much later, in the 13th Century CE, people figured out processes to refine the iron, melting it back down again in a process designed to oxidize some of the carbon and impurities, and give us an iron that’s stronger and easier to work with. We finally had iron that we could work reliably. And it was such a big deal, we named a whole age after it.
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