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

Abstract

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.

Smartness from Below: Variations on Technology and Creativity in Contemporary Kinshasa

“…It appears that the experiment did not work, because the smelting of copper in natural draft furnaces was never attempted again at the site or elsewhere. There are technical reasons; smelting copper in natural draft furnaces reduces more iron, creating a low-utility iron-copper alloy tantamount to wasted effort (Chirikure and Bandama 2014;Craddock and Meeks 1987). If this experiment had worked, we would have seen more copper smelting in natural draft furnaces at the site well into the historical period.…”

Diversity and Variability in the Preindustrial Iron-Smelting Technologies of Great Zimbabwe, Southern Africa

“…The earliest bibliographical study of African metallurgy stopped at the Zambezi River, claiming a lack of relevant literature further south (Cline, 1937). The initial speculative understanding was that the classic type of iron smelting furnace south of the Zambezi was the low shaft type fired by forced draft, in contrast to the multiplicity of types in South and Central Africa (Friede, 1972;Cline, 1937;Chirikure and Bandama, 2014). The low shaft furnace has been found at iron-smelting sites dated to both the Early and Late Iron Age, and was present during colonial times, giving it a record of more than 1500 years of use between the Zambezi and Limpopo Rivers without much variation.…”

A Technology of Multiple Smelting Furnaces per Termite Mound: Iron Production in Chongwe, Lusaka, Zambia

“…According to Mapunda (1995Mapunda ( , 2010, the late start of archaeometallurgical studies is attributable to factors that include biases in professional research interests, funding opportunities, the influence of the first Stone Age including paleoanthropological discoveries and geographical factors (see also Lyaya & Mapunda 2014, and references therein). Chirikure and Bandama (2014) add shortage of research facilities and expertise to the list of factors for late start of archaeometallurgical studies. Because of this situation, there are few African archaeometallurgists compared to other archaeological specializations.…”