Metals from the Ages #2: Bronze Age

After the Copper Age came the Bronze Age. Again, it was a “mix (of) history, geography, physics, geology, and chemistry”, explains Tomas Pueyo in his post. But we are getting ahead of ourselves. First mankind had to find tin and lead. 


 Why those two? Again, from chemistry, same column (group) = similar chemical properties. In this case:

“Because you can make them in a normal fire pit!”

Lead melts at 327° C. A wood fire easily reaches 600-800° C. If the ore of lead found itself in a pit fire, the lead got separated.

“But lead is not very useful because it’s heavy and way too soft. It couldn’t work as a tool or as a hand-held weapon.”

The common ore of lead, galena, has traces of silver. It is likely that humans began to smelt galena for the silver and lead was just a byproduct.

~~

 

Tin has an even lower melting point of 232° C. But it is brittle and rare, hardly a candidate for a useful metal. But in many copper mines, tin is also present. And copper, if you remember from the earlier blog, needed very high temperatures to separate.

“Both metals (copper and tin) would go into kilns at the same time, forming bronze by accident. And bronze is very useful.”

 

How/why is bronze more useful than copper? (1) It is stronger and harder, enabling better tools and weapons. (2) It melts at temperatures achievable by those old human kilns, and the fluid metal could then be cast into different shapes. (3) Oxidized bronze protects the metal under it, unlike copper oxide which is flaky, falls off and so the copper continuously corrodes. (4) Bronze can bounce back into shape, so it began to be used for making axles, hinges and nails.

 

All of this meant bronze tools lasted longer, could be used to clear more forests for agriculture. Plus, those tools could cut wood like nothing before, allowing for the construction of boats and ships larger than ever before. Humans could expand their footprint with the improvements in transportation tech. And trade. It made for better swords and armours and thus facilitated greater militarization. All the pre-requisites for the age of empires were created thanks to bronze.

 

Funnily, as the importance of bronze grew, the need for that unimportant-in-itself metal, tin, also grew (to make bronze):

“The scarcity of tin drove trade.”

But why trade if you can conquer the mines? And so bronze triggered both trade and wars. All of which is why it is called the Bronze Age.

 

On a side-note, the fact that bronze set off both trade and war is similar to how rare earths triggered trade and now friction. As Mark Twain famously said, history doesn’t always repeat, but it sure rhymes.

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