How did ancient civilizations make furnaces hot enough to melt metals like copper or iron with just charcoal, wood, coal, clay, dirt and stone?
In: Engineering
Iron furnaces made of clay and dirt – even if they do work, won’t last for long.
But stone is pretty much universal till today. Correct air flow, charcoal and bellows helped to increase temperatures even more. Worst that could happen to stone furnace is freezing temperatures at night – rapid cooling might crack or even explode the stones. That’s also why they were usually covered with a roof – since rain tends to cool things down way too rapidly.
Everything in nature has (freezing and) melting point, even stones (think lava), and finding out suitable material or type of stone was more or less matter of experimentation. But people, having used rocks (heated in campfire) to warm themselves at night for almost half a million years, were pretty knowledgeable about those by the time of metal smelting.
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