Fuel Efficiency of Ancient Copper Alloys: Theoretical Melting Thermodynamics of Copper, Tin and Arsenical Copper and Timber Conservation in the Bronze Age Levant*

摘要

The melting of pure or alloyed copper, tin and arsenical copper ingots or recycled objects was a drain on the timber and dung fuel resources of many cultures. This paper suggests formulae grounded in thermodynamic principles in an attempt to estimate the energy requirements necessary to melt copper alloys common to both Old and New World cultures, with the goal of identifying consumption and conservation patterns. It has been suggested that tin bronze metallurgy was first adopted in the Levant during the Early Bronze Age (EB) IV, at the onset of the Late Holocene climate episode (c.2300-2000 bc), becoming the most desired alloy by the Middle Bronze Age (MB) II (2000-1530 bc) due to the ease of melting tin. To test this hypothesis, the formulae are applied here to all published Levantine EB IV - MB II copper alloys. Fuel conservation rates are proposed based on the thermodynamic formulae. Tin bronze is demonstrably more fuel efficient than pure copper. Due to the inherent difficulties in predicting the behaviour of arsenical copper compounds, it is suggested that melting experiments with representative alloys are conducted to further test and refine these energy relationships.