Bronze Age Work Hazards

Or: How Hephaestus Got His Limp

At some point, a smith would connect the properties of the bronze ingot with the properties of the ores going into the smelter, which would save him a lot of work and charcoal blending ingot together. At this point the smith is truly master of his craft, and one can easily imagine that the best smiths would have routinely produced bronzes of much higher quality than normal. Smiths take on legendary or god-like form for the first time.

Arsenic ores are more common than tin ores, and make high-quality bronzes: there are no tin bronzes in Western Asia before 3000 BC. Arsenic bronzes do not cast as well, but are as hard as tin bronzes. The choice between arsenic and tin bronze may not have been easy, even when it became available. The choice may have depended on the ores available locally: arsenic/copper ores are common, while copper/tin ores are rare. We don't know accurately how often arsenate ores occur in copper deposits because the question is not important in modern mining. In this case, it is just possible that Chalcolithic miners were better informed than we are!

After 3000 BC, Cretan and Western Mediterranean bronzes were largely made with arsenic, Egyptian bronzes almost exclusively with arsenic, but Anatolian bronzes were made with both. We suspect that Anatolian bronzes were first made with tin extracted from the mineral stannite. It is difficult to distinguish tin-bearing stannite from the arsenic-bearing minerals arsenopyrite and enargite. Possibly the first use of tin ores stemmed from a simple mistake by prospectors searching for more arsenic-bearing ores.

Eventually smiths turned to tin ores even though they were more difficult to obtain than arsenic-bearing ores. Smelters work outside, so fumes can be dispersed in the wind, but a smith cannot help breathing in arsenic fumes as he heats, casts, and hammers hot arsenic-laced bronze. The symptoms of low-level arsenic poisoning develop slowly, usually over a period of years. The most obvious symptoms are gradual nerve damage in the limbs. Eventually smiths must have realized what was happening to them, and what was responsible; and eventually they recognized the danger of working with arsenic alloys. Except in Egypt, where arsenic was used until 2000 BC, tin bronze gradually became the alloy of choice, and the dominant metal of advanced civilizations in the Western World for 2000 years. The long agony of so many Bronze Age smiths has come down to us in legend, however: the Greek smith god Hephaestus and his Roman counterpart Vulcan were lame. This is not an occupational hazard of the Iron Age smiths that forged spears for the Greek hoplites and swords for the Roman legionaries. It reflects the centuries-old folk memory of their predecessors.
[Source is a UC Davis professor's set of notes on historical metalurgy]

That's so dang cool. I'm wishing I could work it into the Elementary Program story about the development of copper and bronze metalworkiing, but I can't think how to get it down short enough. (Having to explain arsenic and all...)