Relationship between furnace structure and slag properties: the case of Fipa and Nyiha Iron Smelting Technology

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university of Dar es Salaam
This dissertation is a comparative study aimed at identifying and establishing the relationship between fumace structures and their resultant slag in Fipa and Nyiha iron smelting technology. Slag and slag-like materials are resistant to post-deposition factors, as a result, they are the most conspicuous and ubiquitous products of traditional iron working compared to the furnace that produced them. Archaeometallurgists have not been able to use it beyond studying its properties. Their correct identification is crusial to understanding technological processes performed at these sites. By using ethnographic information, archaeological survey, mapping and excavation, this research has revealed two different technologies: the Malungu and the Katukutu. These include; four complete Malungu iron smelting furnaces with different sizes, shapes and soil colour; one remains of an iron refining furnace Kintengwe (a variant of malungu technology); and remains of two Katukutu iron smelting furnaces. Furnace and slag identification involved a combination of physical, mineralogical and chemical analysis. On the basis of this investigation it was possible to distinguish between the two different technologies in southwestern Tanzania. Malungu furnaces are the tallest, standing up to 2.8 – 3.1 meters tall with slag that are less magnetic, bulky, and metallic in terms of luster. Whereas, Katubutu furnace are generally globular in shape and less than 1.5 meters tall with slag that are highly magnetic, prone to oxidation and greasy in terms of luster. Interestingly, the mineralogical analysis carried out on the slag from the two technologies showed that they used almost the same mineral composition – quartz, fayalite, hematite, magnetite and microline with difference with Katukutu technology possessing leucite and manganese phosphate hydrate. Thus, there is need for future research to study and analyze more slag samples, chemically and mineralogically.
Available in print form, EAF Collection, Dr. Wilbert Chagula Library, (THS EAF TN707N46)
Iron smelting technology, Furnace, Slag
Uche, N. J (2010) Relationship between furnace structure and slag properties: the case of Fipa and Nyiha Iron Smelting Technology, Masters dissertation, University of Dar es Salaam, Dar es Salaam