Editor’s note: We are pleased to present a series adapted from biologist Michael Denton’s book, Fire-Maker: How Humans Were Designed to Harness Fire and Transform Our Planet, from Discovery Institute Press. Find the whole series here. Dr. Denton’s forthcoming book, The Miracle of the Cell, will be published in September.
Copper smelting requires temperatures between 1,150° and 1,250° C,1 but the smelting of iron requires even higher temperatures,2 more reducing conditions,3 and a “greater blast of air.”4 This required more advanced kilns and more sophisticated techniques.5 Iron smelting was only mastered later, around 1200 BC,6 providing mankind access to the most useful and important of all metals, iron, thus initiating the Iron Age.7
A Leap for Mankind
This was a landmark advance. Because of the ready availability of iron ores throughout the world and the great utility of iron and its alloys (including steel) for the manufacture of all manner of strong and durable tools, from ploughshares to needles, the use of metal tools and knowledge of iron metallurgy spread throughout the old world. The importance of metals, particularly iron, and the importance of the discovery of metallurgy can hardly be exaggerated.
Of course, metallurgy was only one of a host of fire-assisted technologies which followed the mastery of fire, for as Stephen Pyne comments in his Vestal Fire:
In fact almost no device or pursuit has lacked an element of combustion technology… Fire distilled seawater into salt, wood into tar, resin into pitch and turpentine, grain and grape into alcohol; it transformed wood into ash and then into soap, and cooked calcitic rock into lime. Plaster and cement, in turn, encouraged new construction.8
But while ceramics, glassmaking, chemistry, and the host of other fire-enabled technologies were all of great importance in drawing man from the Paleolithic to the 21st century, the birth of metallurgy overshadows all others in importance.
The mastery of fire and the subsequent development of metallurgy and our ability to make and shape complex metal artifacts prepared the stage for the coming of the industrial revolution and the invention over the past five centuries of all manner of complex artifacts and machines, from telescopes and microscopes, to the building of the first artificially powered locomotives. Inventions followed thick and fast: dynamos and electric motors ushered in the modern electric age, the internal combustion engine, the first airplanes, jet engines, and the development of the electronic computer during World War II.
Tomorrow, “Combustion Is Anything but Ordinary.”
- Wilson, 15; Lee Horn, “Fuel for the Metal Worker.”
- Jay King, “The Emergence of Iron Smelting and Blacksmithing: 900 B.C. to the Early Roman Empire,” Roman History, Coins, and Technology Back Pages, 2006, accessed May 17, 2016, http://www.jaysromanhistory.com/romeweb/glossary/timeln/t10.htm.
- The extraction of metals from their ores requires not only heat but reducing conditions to draw the oxygen from the metal. See “Smelting,” Wikipedia, https://en.wikipedia.org/wiki/Smelting; From the article: “Reduction is the final, high-temperature step in smelting. It is here that the oxide becomes the elemental metal. A reducing environment (often provided by carbon monoxide, made by incomplete combustion, produced in an air-starved furnace) pulls the final oxygen atoms from the raw metal.” That the reaction C + O in the kiln not only produces heat but at the same time the highly reducing CO (essential for iron extraction) is an intriguing element of fitness in nature for metallurgy.
- King: “The techniques developed by the copper workers did not generate enough heat to cause iron ore to give up its oxygen. Also, the quantities of carbon monoxide [which generates reducing condition in a kiln] had to be much greater than required for copper. Not only does iron melt at a higher temperature than copper, but iron oxide holds its oxygen atoms much more tenaciously than copper oxide does….The answer was to first make a high quality charcoal from hardwoods….The iron ore would be totally surrounded by charcoal and the furnace had to be more enclosed, having only a chimney to exhaust the fumes and inlets for the bellows supplying the air. Charcoal would first be loaded into the furnace, followed by the iron ore and more charcoal. The fires were lit, and the bellows operators pumped furiously to generate heat capable of adding enough energy to the iron oxide to make it loosen its grip on the oxygen atoms.”
- Harris; “Iron Age,” Wikipedia, May 18, 2016, accessed May 23, 2016, https://en.wikipedia.org/wiki/Iron_Age.
- Stephen J. Pyne, Vestal Fire: An Environmental History, Told through Fire, of Europe and Europe’s Encounter with the World (Seattle: University of Washington Press, 1997), 42-43.