The sword is a weapon full of imagery – of great armies and knights – but it also parallels the metallurgical developments that made its use possible.

Its invention, the date of which is still disputed, grew from the lengthening of daggers. These shorter weapons were originally made from copper, which although readily available is a  relatively soft metal unsuited to anything other than a short stabbing weapon.

The creation of the longer, sharp-edged, swinging and cutting weapon could not occur without the development of a harder metal.  For that reason, its first appearance is thought to be between the 17^th – 16^th century BC in the Black Sea region. This period would later  become known as the Bronze Age.

By adding tin to the copper, a harder alloy (bronze) could be created, which advanced the development of the sword; even though ancient swordsmiths may not have understood all the alloy’s properties, there is evidence that they were able to vary the composition to create different effects depending on their battle priorities. For example, early Chinese swordsmiths preferred to use a higher percentage of tin (circa 20%) to create a harder, though more brittle, sword, whereas other regions used a lower percentage of tin (circa 10%) for a sword less likely to break in battle, although more likely to bend.

It was not until the Iron Age (12^th – 13^th century BC), however, that longer, sturdier swords could be developed.

By smelting raw iron (iron ore) using extreme heat and coal to bind the oxygen in the iron ore, swordsmiths were able to produce swords of almost pure iron with carbon dioxide as a by-product.

Smelting was first made possible through the use of bloomeries, now superseded by the blast furnace. At the time, iron’s high melting point meant that swordsmiths could only produce a porous iron mass called a bloom, which then had to be hammered out over several cycles of heating and cooling in order to produce a sword. It must be said, however, that these iron swords were only slightly better in terms of strength and hardness than the bronze swords before them, but iron was very widely available, and the process was far simpler than that of producing a bronze sword, allowing for larger scale production and bigger, sword-carrying armies, with predictable consequences.

Over time, swordsmiths discovered that by adding charcoal (carbon) during the iron smelting process, and by quenching to increase hardness, then tempering to take away the brittleness, they could make far harder and resilient swords which did not lose their shape. The process was, however, not easy to control and it took centuries before the smiths learned to create the new alloy – steel – in any consistent way. The result was swords of vastly varying quality; indeed into the early Middle Ages, some swords were still being made from iron. It was centuries before the true properties of  steel were understood.

Video: ‘Liquid Fire’ to Metal Sword in minutes, A History of Ancient Britain—Ep4, BBC2  https://www.youtube.com/watch?v=eEWIuyeNp2k

Sources: Gonzalez, R  A brief history of the ancient science of sword making http://io9.gizmodo.com/5831683/a-brief-history-of-the-ancient-science-of-sword-making

The Japanese Samurai Sword