Macroscopic and microscopic variation of iron and high carbon steel production in the southern highlands of Tanzania

One essential feature of African iron production process is that it is greatly variable in culture and technology. The early research focused on some themes: origins, culture, and how iron was produced, which were investigated using archaeological, ethno- archaeological, and experimental methods. The purpose of this thesis was to examine the relationship between macroscopic and microscopic variation of iron and steel production in the southern highlands of Tanzania. I used field methods: ethnographic inquiry, surface and sub-surface survey, mapping, and excavation; and laboratory analytical techniques: firing, optical and electron microscopy, microanalysis, and X-ray fluorescence to investigate the research theme. The results indicate that there is a strong relationship between macro- and microscopic variation of iron and steel production in terms of the use technical ceramics with good refractory qualities, the presence of the three stage process in Ufipa and Unyiha, involving a refining stage between the smelting and smiting stages; the liquid slag handling techniques, the reduction efficiency, and the nature of the final products: soft iron and carbon-rich steel. Although there are macroscopic data on the use of forced- and natural-draft furnaces in the region, it is difficult to microscopically verify the air supply mechanisms in the region. This work recommends that in order to avoid the confusion on the three stage process and relationship between macro- and microscopic variation in iron and steel production, the role of matrix and provenance should be given due weight as laboratory analyses.