How did ancient civilizations make furnaces hot enough to melt metals like copper or iron with just charcoal, wood, coal, clay, dirt and stone?

Question

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

Answer 1

Lets look at temperatures first.

Charcoil burning temperature 980 C. With propper air pumping it goes to 1200.

Copper melting point around 1100.
Bronze (copper and tin) melting point 913 C
Iron 1538C.

So charcoil is enough to completly melt copper to nake more usefull bronze. That allows to to puur liquid bronze into forms for mass production ( eg arrowheads, swords, sizors etc)

Iron is a bit different story. While it is possible to malt iron in furnance it creates a lot of problems for iron quality. Which greatly limits iron use (it easy to bend, has no retraction, does not keep edge etc). Thats why iron require forging with hammer to reduce impurities. That for long time was expensive ( mire expensive than making bronze tools) activity which produced low quality tools. Basicly sole iron usage untile 8 century CE iron mainly used in chainmails as non of it negative traits were important in chainmails.