Browsing by Author "Lyaya, Edwinus Chrisantus"

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    Macroscopic and microscopic variation of iron and high carbon steel production in the southern highlands of Tanzania
    (University of Dar es Salaam, 2013) Lyaya, Edwinus Chrisantus
    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.
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    The physical properties of metalliferous slag a comparison between smelting and something processes
    (University of Dar es Salaam, 2007) Lyaya, Edwinus Chrisantus
    African iron working technology involved smelting, refining, and smithing technological and functional processes or stages. These produced three respective metalliferous slag types namely smelting slag, refining slag and smithing slag. Unfortunately, not all writers are clear with the distinction of the three types. Some recognize smelting slag alone, others recognize smelting and smithing slag, and yet others confuse between refinery and smithing slag. This work examines the physical properties of metalliferous slag with emphasis on smelting and smithing. It has left out refinery slag because not all smelted iron was refined, but all smelted iron was ultimately forged. The examination is based on samples from incontrovertible smelting and smithing sites. Physical attributes for each type of slag have been identified with a view to establish distinguishing criteria between smelting and smithing slag. The research has found out that smelting and smithing slag are quite different in terms of general size, mass or weight, density, morphology, thermal condition, magnetism, fragmentation, weathering, and surface conditions. This work shows that the two are closely related in such attributes as luster, color(s), porosity, inclusion, impressions and source materials. Through the study of the physical attributes, it is therefore possible to distinguish smelting from smithing slag, and so smelting from smithing sites. However, the role of matrix and provenience is also important in ascertaining the two categories.