Métallurgie du fer et Sociétés africaines Bilans et nouveaux paradigmes dans la

Métallurgie du fer et Sociétés africaines Bilans et nouveaux paradigmes dans la recherche anthropologique et archéologique Édité par Caroline Robion-Brunner Bruno Martinelli BAR International Series 2395 2012 Cambridge Monographs in African Archaeology 81 Series Editors: Laurence Smith Cambridge Monographs in African Archaeology XX Series Editors : John Alexander and Lawrence Smith Métallurgie du fer et Sociétés africaines Bilans et nouveaux paradigmes dans la recherche anthropologique et archéologique Caroline Robion-Brunner et Bruno Martinelli BAR International Series XXXX 2012 Published by Archaeopress Publishers of British Archaeological Reports Gordon House 276 Banbury Road Oxford OX2 7ED England bar@archaeopress.com www.archaeopress.com BAR S2395 Cambridge Monographs in African Archaeology 81 Métallurgie du fer et Sociétés africaines: Bilans et nouveaux paradigmes dans la recherche anthropologique et archéologique © Archaeopress and the individual authors 2012 ISBN 978 1 4073 0988 0 Le colloque a été organisé avec le soutien des institutions suivantes Centre d’Etudes des Mondes Africains (CEMAf-UMR 8171) Maison Méditerranéenne des Sciences de l’Homme Université de Provence Programme ANR Systèmes de Savoirs et d’apprentissage (SYSAV) Laboratoire Archéologie, Terre, Histoire, Sociétés (ARTeHIS-UMR 5594) Programme CORUS 2 (6116) Impacts anthropologiques et climatiques sur la dynamique éolienne et les aérosols terrigènes Laboratoire Travaux et Recherches Archéologiques, Cultures, Espaces et Sociétés (TRACES-UMR 5608) Comité scientifique Caroline Robion-Brunner (TRACES-UMR 5608), Bruno Martinelli (Université de Provence), Philippe de Barros (Palomar College), Alain Gallay (Université de Genève), Annabelle Gallin (LAMPEA- UMR 6636), Eric Huysecom (Université de Genève), Gaspard Pagès (Université de Liège), Vincent Serneels (Université de Fribourg) Comité d’organisation Caroline Robion-Brunner (TRACES-UMR 5608), Bruno Martinelli (Université de Provence), Caroline Testanière (CEMAf-Aix) Graphisme Couverture : Antoine Constans; Mise en page : Antoine Constans; Gestion des fichiers : Caroline Robion-Brunner et Antoine Constans Printed in England by CMP (UK) Ltd All BAR titles are available from: Hadrian Books Ltd 122 Banbury Road Oxford OX2 7BP England www.hadrianbooks.co.uk The current BAR catalogue with details of all titles in print, prices and means of payment is available free from Hadrian Books or may be downloaded from www.archaeopress.com The Bloom Refining Technology in Ufipa, Tanzania (1850-1950) Edwinus C. LYAYA1,2, Bertram B. MAPUNDA2, Thilo REHREN1 1 UCL Institute of Archaeology, London 2 UDCASS, Department of History and Archaeology, Dar es Salaam La variabilité des processus sidérurgiques en Afrique a occasionné une classification de ses vestiges peu claire. Le but de cet article est de découvrir si l’on peut rapprocher ou différencier macroscopiquement, chimiquement et microscopiquement le processus de raffinage de celui de la réduction de fonte. Macroscopiquement, les sites de raffinage sur le terrain peuvent être différencié de ceux de réduction sur la base de la taille du secteur, la morphologie des scories, la quantité et la composition des déchets. Chimiquement, il est difficile de distinguer les deux processus, toutefois il y a une différence significative lorsqu’on analyse leurs microstructures respectives. La scorie de raffinage contient principalement des prill de fer de forme arrondie indiquant un important processus de réduction, alors que celle de réduction comprend des particules de fer ferrique de forme plus angulaire. Ces résultats indiquent que le processus de raffinage a dû agglomérer des fragments de scories et de fer à l’intérieur d’une masse de métal riche en carbone. Analyses métallographiques et chimiques, loupe de réduction et de raffinage, prill de fer arrondi, scorie, Tanzanie. The classification of African metalliferous relics generally lacks clarity, because African ironworking involved variable processes. The purpose of this paper was to find out how the refining process was related to or different from the smelting process, macroscopically, chemically, and microscopically. Macroscopically, refining sites or clusters in the field can be differentiated from smelting clusters based on attributes such as area size, slag morphology, quantity and composition of the remains. Chemically, it has been difficult to draw a line between the two processes, but there is a significant difference between the two based on microstructural analyses. Refining slag principally contain roundish iron prills indicative of a highly reducing process if compared to the smelting process, which results in more angular ferritic iron particles. These results indicate that the refining process was meant to consolidate incoherent and slag-rich bloom fragments into larger, denser and possibly more carbon-rich metal ready to be forged into high-quality implements. Metallography and chemical analysis, smelting and refining bloom, roundish iron prills, metalliferous, slag, Tanzania. 195 E. C. Lyaya et al. Introduction Bloomery ironworking is generally assumed to have involved two processes, namely smelting and smithing. This two- stage technology has been documented in most parts of the Old World, including southern Africa (e.g. Miller and Killick 2004; Chirikure 2006, 147; Chirikure and Rehren 2006), west Africa (e.g. Filipowiak 1985, 36), eastern Africa (e.g. Sutton 1985; Larick 1986; Childs 1996; Barndon 2004, 76; Craddock et al., 2007), and central Africa (e.g. Van Noten and Raymaekers 1988, 106). These scholars have generally established that the bloom resulting from the smelting process was re-worked during the smithing stage in order to forge tools. Although this assumption is widely accepted, it ought to be rethought for some regions, because it does not give due weight to an intermediate process which involves bloom refining in a special furnace prior to smithing. A separate refining tradition set between smelting and smithing is well documented in central and eastern Africa (Greig 1937; Chaplin 1961; Brock and Brock 1965; Wembah-Rashid 1969; Davison and Mosley 1988; Mapunda 1995a; Barndon 2004), and is thought to improve the quality of the bloom prior to smithing, and possibly also to enhance the overall iron yield. Just as smelting and smithing processes, this second stage in the ironworking chaîne opératoire (Barndon 2004, 92) produced its own slag. The presence and acceptance of refining as a separate technological process calls for a rethinking of the classification of metalliferous relics. For this, we need to investigate what refining slags look like, and how they are different from smelting and smithing slags. Based on theoretical considerations, we expect that refining slag should look different from smelting and smithing slags, because the three ironworking processes were both technologically and functionally different from each other. In particular, based on ethnographic reports and the idea of re-smelting an incompletely consolidated bloom, the refining slag should reflect more reducing conditions and a larger contribution of fuel ash to the slag formation than the smelting slag. A full examination of the refining process is indispensable because it will give the process its due weight, and will enhance clarity on metalliferous slags. This paper presents the results of an initial archaeometallurgical study of Fipa refining slag from the Pito ward in Sumbawanga, Tanzania (Fig. 1), with the view of comparing it to associated smelting slags macroscopically, chemically, and microscopically. Background Information to Fipa Ironworking Technology The name Fipa comes from the word ‘lyamfipa’, meaning plateau people (Wembah-Rashid 1969, 65; Mapunda 2004, 75). The Fipa are famous ironworkers. Traditionally they lived in upland (plateau) regions, often where water, iron ore and termite mounds were plentiful, as these were essential for their basic needs, especially iron working (Mapunda 2010). The Fipa practised a three-stage ironworking tradition, involving smelting, refining, and smithing. Despite the fact that they were banned from smelting iron during the colonial period, they continued producing iron until the second half of the 20th century, due in part to the inaccessibility of Ufipa (the land of the Fipa), which not 196 Fig. 1 : Pito Ward, Sumbawanga, in Ufipa, SW Tanzania The Bloom Refining Technology in Ufipa, Tanzania (1850-1950) only impaired checks by the colonial authorities but also hindered the influx of imported metalware. Noteworthy that because Fipa ironworking medicines, which were important to help the smelt turn out successfully, were controlled by the master smelter, the Fipa are well-known for traditional healing in modern day Tanzania, which is a reflection of the socio-cultural impact of ironworking (Mapunda 2004). Because of these reasons, there is substantial information that has been published on Fipa ironworking technology. The Fipa ironworking historiography began with amateur ethnographers and anthropologists in the 1910s, followed by professional ethnographers and anthropologists in the 1960s. These early writers, including Wychaert (1914), Greig (1937), Wise (1958), and Wembah-Rashid (1969), focused on documenting and producing descriptive reports of Fipa ironworking, which were based on interviews with retired smelters and observations of smelting processes, especially when the retired smelters were commissioned to demonstrate the process. After the amateur and professional ethnographers and anthropologists, the period between the 1970s and 2000s was marked by the work of ethnoarchaeologists and historical archaeologists. These later researchers had a different approach to the investigation of the Fipa iron technology, and have systematically studied different themes of Fipa ironworking, including the social history, culture and socio-cultural implications of ironworking. This group includes Sutton (1985), Barndon (1992; 1996; 2004), and Mapunda (1995a; 1995b; 2003; 2004). According to archaeological research conducted so far in Ufipa and neighbouring areas, between 400 and 1000 AD ironworking was already being practised there (Clark 1974). This understanding is based on metallurgical relics found in association with the Kalambo pottery tradition, which is related to Urewe ware in the interlacustrine region, and the uploads/Societe et culture/ the-bloom-refining-technology-in-ufipa-t.pdf

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Société et culturerefining smelting technology slags ironworking
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