Cast iron is very commonly reported in analysis of African bloomery
smelting sites, both prehistoric and historic. I know of no case in
which it was tapped from the furnace in liquid state, and presume that
the couple of instances of this reported in Walter Cline's Mining and
Metallurgy in Negro Africa (1939)are mistaken observations by ignorant
observers. If you want to look at a couple of publications with
micrographs of cast iron from bloomeries, try Peter Schmidt's Iron
Technology in East Africa (1998) or N. David, R. Heimann, D. Killick and
M. Wayman
(1989) Between bloomery and blast furnace: Mafa iron-smelting technology
in North Cameroon. The African Archaeological Review 7:185-210.The
former is from Tanzania, the latter from Cameroon. I have personally
examined under the microscope further examples from Ghana, Côte
d'Ivoire, Kenya and South Africa.
It seems to me that the production of cast iron is within the normal
range of operation of most hand-blown shaft bloomeries. My subjective
impression is that cast iron and bloomery steel are more commonly seen
in African than European bloomeries, and that this is probably because
most African bloomeries are a lot larger (75 cm - 120 cm internal
diameter, with 4 or more tuyères, than most European bloomeries. Even
the earliest known African bloomeries, from the mid-first millennium BC,
are of this size.
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