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 2 1 9 A previous contribution to AM&P’s series on archaeometallurgy pre- sented a brief overview of production and process metallurgy for copper and silver alloys in the Old World[1]. Consistent developments of these technologies began around 3500 B.C., with bronzes becoming so important that the period from about 3300 to 1200 B.C. is commonly referred to as the Bronze Age. However, dates vary considerably according to geographical locations, and the Bronze Age is usually subdivided into Early, Intermediate, and Late periods, again with differing dates. Thisarticleprovidesabroadlysimi- lar overview for the Iron Age, which dates from approximately 1200 to 500 B.C. As before, the dates vary according to geographical locations and the relative sophistication of the production and processing techniques. A recent survey of the beginnings of iron in the Near East is given by Erb- Satullo[2]. He argues, like others, that iron- smelting technology was derived from the earlier developments of copper- smelting. This is very likely because the technology is complex, with many difficulties to overcome. This has been amp- ly demonstrated by modern-day experimental archaeometallurgy. These difficulties are described in this article. Before discussing ancient iron pro- duction and processing, note that without these and much later developments, beginning in the mid-18th century A.D., the Industrial Revolution would have been more problematic. Although there were many contributing causes of the Industrial Revolution, the development of large-scale iron and steel production, particularly for manufacturing industrial machines and tools, played a major role. ANCIENT IRON PRODUCTION The very beginning of iron smelting is uncertain. From the middle of the 19th century A.D. until the 1970s the concept of bowl furnace smelting was generally favored[3]. However, experiments have shown that this method is usually unsuccessful[4], but it is possible to obtain small amounts of partly consolidated iron using high-quality iron ores[5]. Regular iron smelting in the Old World was preceded by about 2000 years of copper and bronze production, by which time shaft furnaces for copper smelting were well-developed[1]. Thus, it might seem logical that iron smelting could be done in a similar fashion. However, there were, and are, major differences. Firstly, iron cannot be melted in a shaft furnace, but accumulates as a porous mixture of iron and slag called a “bloom.” Secondly, the operating conditions are (much) more complex. A schematic of an iron smelting shaft furnace and the various production stages and their locations is shown in Fig. 1. This schematic is based on experiments with a Hungarian shaft furnace design from the 10th century A.D.[6] In the present context this is anachronistic, but the design is generically representative, and the experimental study has the considerable advantage that it is combined with details of the production stages[6]. The schematic in Fig. 1 shows that shaft furnace iron smelting consists of pre-roasting iron ore and its subsequent reduction in a multistage process. The complexity of this furnace reduction would not have been recognized by the ancient ironmasters. Successful smelting also requires[7,8] (and would have required) an empirically determined optimum combination of the following parameters: furnace size, tuyère position, forced air volume, the type and size of ore particles, size of the charcoal, and the sequence of adding charcoal and ore[7,8]. Much more information about shaft furnace iron smelting is given in Ref. 6‒8. When a bloom is removed from the furnace it is spongy, consisting of a mixture of iron and slag. It is therefore first consolidated by hammering that squeezes out as much slag as possible. If too large to be hammer-forged by hand, the bloom is then split with a maul driven by sledgehammers. ANCIENT IRON PRODUCTION AND PROCESSING IN THE OLD WORLD A look at processing and production of iron during the Iron Age, 1200 to 500 B.C., including early unintentional forms of steel. Omid Oudbashi, Art University of Isfahan, Iran Ümit Güder, Alexander von Humboldt Fellow, Max-Planck-Institut für Eisenforschung, Germany Russell Wanhill, Emmeloord, the Netherlands
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