Indigenous African Furnace Types and Slag Composition—Is there a Correlation?

Within variation, three major iron smelting furnaces were used in the Iron Age of sub‐Saharan Africa, ranging from the natural draught driven tall shaft to the forced draught powered low shaft and bowl furnaces. These furnace types are, however, mostly known from the ethnographic context. Often, archaeologists are confronted with remnants from the smelting process, forcing them to speculate on the anatomy of the extant furnaces. The presence of multiple fused tuyeres has been used to identify natural draught furnaces in the archaeological record. However, working back from smelting remains such as slag to the furnace type using physical and chemical evidence has generally proved to be ‘undoable’. Thus, when randomly selected, the chances are high that one cannot separate bowl furnace slags from those that formed in their tall or low shaft counterparts. This observation is hardly unexpected; analogous thermodynamics and thermo‐chemical reactions governed bloomery smelting irrespective of furnace type. Rehren et al. (2007) have labelled this phenomenon the ‘tyranny of system driven constraints’. In this study, we argue that the hierarchical use of statistical methods may add another layer of evidence which, when coupled to archaeological indicators, may be useful in correlating slag chemistry to furnace types used in antiquity.     

An assessment of the magnetic response of an iron‐smelting site*

The magnetic response derived from an iron‐smelting site was investigated by comparing magnetometry and magnetic susceptibility geophysical survey data and laboratory analyses of the magnetic characteristics of the furnace and slags. Magnetic analysis and microscopy (optical and SEM) of samples from the furnace lining and the slag deposits demonstrated the heterogeneity in the magnetic, morphological and mineral compositions of both materials. The comparison of the magnetic characteristics of the material with the geophysical survey data illustrated the importance of using both magnetometry and magnetic susceptibility survey techniques to maximize the information from an iron‐smelting site. The furnace was dated archaeomagnetically to the 14th century ad . The results demonstrate that the magnetic analysis of iron‐smelting sites is highly valuable, both to characterize sites and to improve the understanding of early iron‐working technology.     

斯里兰卡的冶铁考古

介绍了斯里兰卡20世纪80年代以来冶铁考古研究所取得的成就。古代斯里兰卡的铁产品主要是块炼铁和高碳钢,冶铁技术主要有阿腊口腊瓦瓦的自然通风竖炉和以季风为鼓风动力的撒马纳腊瓦瓦开放性矮炉两种,可能与缅甸的自然通风竖炉、日本的踏踏拉以及西非的多哥兰地区抽风式竖炉存在某些历史联系。     

A Rock‐Magnetic Quest for Possible Ore Sources for the Ancient Iron‐Smelting Industry in the Olkhon Region (Lake Baikal,Siberia)

Rock‐magnetic techniques were used to examine the topsoil layer of Kurma archaeological site (in the Olkhon region, on the north‐western coast of Lake Baikal, Siberia) in an effort to determine the possible sources of iron ores for iron‐smelting centres (at about the bc /ad boundary). Measurements have shown a magnetic enhancement of the topsoil due to magnetite grains resulting from weathering of strongly magnetic crystalline rocks. They have also revealed a preliminary picture of the distribution of strongly magnetic topsoils around the ancient iron‐smelting centres. Perhaps, in addition to traditional sources of raw materials, the ancient metallurgists used black sand talus as an ore deposit.     

A discussion of magic and medicines in East African iron working: actors and artefacts in technology

Through an inquiry into locally constructed, pre‐industrial Tanzanian iron smelting practices this article looks beyond social representation of technologies and suggests a more nuanced perspective than the more familiar rituals of transformation and gendered procreative paradigm. It is demonstrated that among the Pangwa and Fipa peoples iron smelting symbolism was not merely a social representation of “something” else and of something of greater significance such as religion, economy and politics, rather there were no real distinctions between technology and other spheres of life; there was no (ontological) difference between humans and non humans. Drawing on inspiration from phenomenology and semantics, as well as Actor Network Theory, I will argue that among Fipa and Pangwa iron workers the use of magic and medicines, as well as an overall thermodynamic conception of the body, was transferred from personal and collective lived experience by metaphorical imagination to the iron smelting furnaces.     

GIS在北京延庆大庄科辽代冶铁遗址群景观考古研究中的初步应用

以北京延庆县大庄科乡冶铁遗址群为例,对空间结构及其与资源、环境间的关系通过GIS工具进行分析。根据对冶炼活动有显著关系的影响因子,建立遗址分布之间的定量关系,进而模拟小区域范围内的遗址预测。研究发现,该区冶铁遗址群对地理位置中的坡度和高程因素展现出较强的依赖性,主要表现为遗址的坡度(7°以下)和高程(650m以下)数值均相对较小;遗址与水系间联系明显,冶铁遗址主要集中在河流交汇处,方便冶炼过程及相关活动水源的供应;而随着冶炉容积(即冶铁产量)的增加,小范围内的冶铁遗址选择,并未以铁矿资源距离就近为最佳选取原则,表明了人类生产活动中对资源的依赖程度有所减低。     

济南运署街汉代铁工场遗址的相关问题探讨

为探讨济南运署街汉代铁工场遗址的性质和冶炼技术,应用X-射线荧光、X-射线衍射、热膨胀测温等方法,对遗址出土的部分遗物进行了相关分析。结合出土实物和测试结果,可以推断运署街遗址是汉代一处兼有冶炼和铸造的铁作坊。陶范、耐火砖、铁渣及矿石原料等冶铸遗物的分析指出,当时的矿石分选、加工、冶炼、铸造技术已经十分成熟,在一定程度上反映了汉代冶铁业的工艺水平。     

Early copper smelting at Itziparátzico,Mexico

Archaeological fieldwork and archaeometallurgical analysis have identified a Late Postclassic regional centre of copper production in western Mexico. The total output from a single unit of production at the site of Itziparátzico is an estimated ten tons of copper and nearly forty tons of slag over the lifetime of the installation. It is argued that this smelting was based on slag-tapping furnaces, a technology previously unknown from Mesoamerican archaeological sites. The smelting site is in dense woodland with ample fuel supply, some 125 km from the next mining area with documented contemporary ore extraction; the copper produced would have been passed on to the capital, another 60 km away, for further distribution and working. The scale of production at Itziparátzico indicates that copper smelting was done by part-time specialists embedded in a predominantly agricultural economy, and formed part of a centrally organized network of mining, smelting and processing of copper to supply the Tarascan state.     

A Sixteenth-Century Wealden Blast Furnace: A Report on Excavations at Panningridge,Sussex, 1964-1970

Abstract

The excavation recovered evidence for two periods of iron smelting; there were substantial surviving structures from a blast furnace thought from documentary sources to have produced pig-iron from 1542 until at least 1563 and, superimposed, indications of a later furnace built with major changes in layout at some time after 1563 but abandoned well before 1611. It was possible to compare, in particular, the application of water-power in the two periods and to sample ore and cast iron. The features of the first furnace could be related to references in surviving account books, and thus a yardstick may be offered for future fieldwork on undocumented furnaces of the period.     

Computational simulation of air flows through a Sri Lankan wind-driven furnace

Research carried out in the early 1990s in Sri Lanka, combining field survey, ethno-archaeology and excavation, revealed an extensive iron producing industry dating to the second half of the first millennium AD. The field evidence indicated that this industry was based on a shallow, wind-powered furnace design that represented a radical departure from the accepted bellows-driven, shaft furnace model which has been the epitome of successful pre-industrial iron smelting. Subsequent experimental reconstructions of the process carried out in Sri Lanka established that the furnaces were wind-powered and also that they were capable of producing high quality, hypereutectoid steels. The objective of the current work is to use modern techniques in Computational Fluid Dynamics (CFD) to investigate the airflow through and around these furnaces in order to verify the theoretical model of their operation. It also demonstrates the potential application of CFD to the modelling and interpretation of pre-modern pyrotechnologies.     

REGIONAL VARIATIONS IN BLOOMERY SMELTING SLAG OF THE IRON AGE AND ROMANO‐BRITISH PERIODS*

This study highlights regional variation in the composition of iron‐smelting slag produced in England prior to the medieval period and attempts to link slag composition to the type of ore smelted. For many sites, the slag compositions were consistent with the use of limonite ore, but there is evidence that siderite ore was smelted at sites in Sussex in the late Iron Age/Romano‐British periods. A compositional comparison of smelting slags and slag inclusions in Iron Age currency bars, using data from Hedges and Salter (1979 ), illustrates the potential of smelting slag compositional data in provenance studies of early iron objects.     

Ancient Mining and Smelting Activities in the Wadi Abu Gerida Area,Central Eastern Desert,Egypt: Preliminary Results

Old mining and smelting features in the Abu Gerida area have been studied using field observations, microscopy and SEM–EDS to detect the ores that were exploited in antiquity. There are two groups of shafts in the area. The first group encloses secondary copper minerals and is associated with glassy slags containing copper prills. The other group is associated with hematite that was extracted and transferred to a smelting station to the west of the mining site, where iron slags and charcoal fragments are found. These slags are composed mainly of wüstite, fayalite–kirschsteinite and traces of metallic iron. Pottery fragments from this area were dated to the Ptolemaic Period, which may be the age of iron exploitation. Copper might have been exploited earlier.     

Iron smelting and smithing in major urban centers in Israel during the Iron Age

By-products of iron production, mainly slag and bloom fragments, unearthed at three Iron Age urban centres in Israel (Hazor, Tel Beer sheba and Rehov), were analysed in order to better understand the organization of iron production during the Iron Age. The production remains studied are all dated not earlier than the Iron Age IIA, and thus shed light on a period of transition from bronze to iron production. Chemical composition and microstructural analyses enable us to determine that both the smelting of iron ores and the refining of the bloom took place within the urban centres of Hazor and Beer-Sheba. We show that slag cakes are the products of smelting, possibly carried out in pit-furnaces. Hammerscales, products of primary and secondary smithing, were attached to slags. From these observations we infer that all stages of iron production were practiced in these urban centres.     

Chemical and mineralogical examination of metallurgical ceramics from a Late Bronze Age copper smelting site in Cyprus

For metallurgical processes in antiquity functional materials were required, which were sufficiently heat resistant. Commonly, ceramics were used for the production of furnaces, tuyères and crucibles. Because normal pottery usually could not withstand the extreme temperatures, which were needed for metallurgical operations, the ceramic production process had to be modified. An analytical case study will be presented on refractory ceramics from the Late Bronze Age copper smelting site Politiko-Phorades (Cyprus). Cyprus had a major role in copper production, starting from this period, and the selected site is the earliest primary smelting site discovered in Cyprus until now. Furnace and tuyère fragments were analysed chemically and mineralogically, in order to investigate ancient ceramic technology in view of heat resistance.     

‘DE CAERIMONIAE’ TECHNOLOGICAL CHOICES IN COPPER‐SMELTING FURNACE DESIGN AT EARLY BRONZE AGE CHRYSOKAMINO,CRETE*

The excavation of a number of Early Bronze Age sites in the Aegean has recovered perforated ceramic fragments. Archaeometallurgical analysis of slag adhering to these fragments indicates that they are the remains of copper‐smelting furnaces. Despite compelling analytical data supporting this identification, no attempt has been made, thus far, to establish how these unusual furnaces may have operated. The use of perforations is poorly understood and can be considered a counter‐intuitive solution for the reduction of oxidic copper ores. The experiments reported here explore the possible technological choices made by the ancient metalworkers of Chrysokamino to ensure the effective reduction of copper minerals. Temperature data and slag samples were obtained to ascertain the technical performance of the furnace structure with, and without, perforations. Possible reasons are given for the use of a perforated design, and the implications of such technological choices are considered.     

Metallurgical Characterization of A Coated Roman Iron Coin By Analytical Investigations

A coated Roman iron coin from Villa Loig in Salzburg, Austria was investigated. The coating is a copper alloy consisting of Cu, Pb, Sn, Zn and negligible amounts of Ag, a variant of gunmetal known as ‘leaded red brass’. The numismatic term for such a coin is subferratus (Latin). From an archaeometallurgical point of view, information about the chemical composition, the microstructure and the manufacturing technique are of interest. To achieve these objectives, different analytical techniques and metallographic examinations were applied. Droplet‐shaped iron inclusions were observed in the red brass coating, while at the grain boundaries, inside the iron core, copper and lead were detected (liquid metal embrittlement). The dendritic microstructure of the coating, the spheroidal‐shaped iron inclusions in the coating and the liquid metal embrittlement show that the iron coin was plated by immersing it in a molten copper alloy. The iron core is a low‐carbon steel with slag stringers, both of which are characteristic of a bloomery iron. Deformation twins (Neumann lines) were observed in the microstructure of the iron core and indicate that the coining was performed after the flan was cooled.     

Investigating the production provenance of iron artifacts with multivariate methods

The quest for suitable data, data treatments and statistical methods for identifying the provenance of iron artifacts has led to a variety of analytical strategies. Researchers working on the problem have been slow to develop or adopt the use of multivariate statistical techniques, despite their successful implementation in other archaeomaterials sourcing frameworks. This paper explores the analytical potential of a comprehensive multivariate statistical strategy for identifying the primary production origins of bloomery iron artifacts using bulk chemical analyses of bloomery smelting slag and slag inclusions in iron artifacts. This strategy includes a multivariate model for identifying distinct slag inclusion types introduced during smelting and refining. Principal component analysis and linear discriminant analysis are then applied to smelting slag training sets to create multivariate provenance fields, the chemical distributions of which are defined by kernel density estimation. Single and multi-group evaluation methods are examined. Appropriate data transformations are discussed to facilitate the projection of the chemistry of “unknown” slag inclusions into the multidimensional space generated by the smelting slag groups of known provenance. The efficacy of this strategy is demonstrated through its application to a previously examined data set derived from three iron production experiments and a published archaeological example. Results indicate that an appropriately designed multivariate strategy can be an effective tool for evaluating provenance hypotheses for bloomery iron artifacts.     

A survey of the charcoal-fuelled ironworking industries of Carmarthenshire and Pembrokeshire

Abstract

A project carried out in 2001 recorded the most important surviving remains of charcoal-fuelled blast furnaces and forges in Carmarthenshire and Pembrokeshire, and reviewed the documentary evidence relating to them. The earliest sites date to the end of the 16th and the early 17th century. The furnaces at Ponthenri (Carmarthenshire) and Blackpool (Pembrokeshire) and the forges at Llandyfan (Carmarthenshire) were surveyed. One furnace site (either Ponthenri or Pontiets) may retain below-ground evidence for experiments in coke smelting by Hugh Grundy in 1620, giving it considerable national importance. These monuments are little known; attention is drawn to their steadily deteriorating condition.