Variability in copper and bronze casting technology as seen at Bronze Age Godin Tepe, Iran

Excavations at Godin Tepe - a Bronze Age site in the Kangavar Valley of the west-central region of Iran - yielded a metal assemblage of 202 artifacts of which 91 are curated at the Royal Ontario Museum, Toronto, Canada. The assemblage consists of decorative objects (figurines, vessels, bracelets, rings, needles, pins) as well as weapons and tools (chisels, blades, daggers, and projectile points). Secondary dendrite arm spacing was measured on polished and etched metallographic sections of the eight samples that display cast structures. Cooling rates were calculated base on these measurements along with the average composition of the metal. Comparison to reference data shows that these cooling rates group into ranges typical of quenched and furnace cooled environments. In addition, the maximum temperatures reached during smelting and casting were estimated based on the microstructure and composition of technical ceramics and slag fragments. Composition and microstructure information was obtained for these artifacts with the use of scanning electron microscopy and electron beam microprobe.