AMP_05_July_August_2021_Digital_Edition

A D V A N C E D M A T E R I A L S & P R O C E S S E S | J U L Y / A U G U S T 2 0 2 1 2 4 M etals and alloys constitute an essential part of the develop- ment of societies from Neolith- ic times, and the earliest process metal- lurgy, melting and consolidation of na- tivemetals, may be tracedback to about 6000 B.C. The importance of metals technology in ancient societies is shown by referring to the main periods of post- Neolithic prehistory as the Copper, Bronze, and Iron Ages [1] . Approximate dates for the beginnings of these tech- nologies in the Near East areas are: cop- per (6000 B.C.), bronzes (3500 B.C.), and iron (1500 B.C.). However, recent data suggest that complex tin bronzes were smelted much earlier in the Balkans, around 4500 B.C. [2] , but this technology was effectively lost after 4000 B.C. Understanding process metallurgy in the ancient world is a major remit of archaeometallurgy. Over the last 50 to 60 years there have been international efforts to establish and promote scien- tific studies of (i) metallurgical process- es and artifacts, from raw materials to final production, and (ii) by-products, tools, and equipment, e.g., slags, cruci- bles, and furnaces (Fig. 1). These studies use a wide range of modern scientific methods and labora- tory instruments to better understand the complex processes involved, and also the artifacts themselves and their eventual deterioration (especially cor- rosion) over the millennia. This latter aspect is directly linked to conservation and restoration techniques. The difficulties that had to be overcome are well demonstrated by ex- perimental archaeometallurgy, i.e., py- rometallurgical experiments to smelt metals from ores in ancient-style cru- cibles and furnaces. Even with modern scientific knowledge these experiments may be only partially successful and sometimes fail completely. Such exper- iments enable a veritable appreciation of the empirically derived skills of an- cient metalworkers. This article gives a brief overview of the production and processing of ancient bronzes and silver in the Old World, and also mentions post-pro- cessing problems including corrosion and embrittlement, owing to long-term burial before archaeological recovery. ANCIENT COPPER ALLOYS The first evidence of using na- tive copper to make small and decora- tive objects comes from the Near East and Caucasus and is dated to about 8000 B.C. [1] . Processing native copper by melting and casting began around 6000 B.C., and reduction of copper ores (smelting) to derive copper began around 4000 B.C. It is important to note that the ores were mined from copper sulfide deposits, where the weathered upper lay- ers consisted mostly of copper carbonates and ox- ide. These could be simply added to smelting cruci- bles and furnaces. How- ever, continued mining reached the sulfide depos- its, and these had to be oxidized (roasted) before smelting. ARCHAEOMETALLURGY OF COPPER AND SILVER ALLOYS IN THE OLD WORLD The production and processing of advanced materials, namely metals and alloys, began in the Old World about 8000 years ago and developed over many millennia, providing a lasting legacy for modern civilizations. Omid Oudbashi, Art University of Isfahan, Iran Russell Wanhill, Emmeloord, the Netherlands Fig. 1 — Schematic of the main aspects of archaeometallurgical studies. Adapted fromBayley et al. [3] .

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