Quote:I'll draw everyone's attention to this post by Mike Bishop, concerning segmentata plates and the Carlisle iron scale collar, and how there may have been iron casting involved.
http://www.romanarmy.com/rat/viewtopic. ... 0847#60847
If this is in reference to Fulford et.al's article (In defense of Rome ; a metallographic investigation of roman ferrous armour from northern Britain) they are not talking about cast iron in the process itself; they are talking about the possibility of the iron of the Carlisle Arm Guard (sample 1, ill. 1-2, page 246) having been made of iron (they reference two italian articles to similar possibilities from the late roman or early medieval period) that had been produced as pig/cast ("grey") iron a a by-product of the bloomery process and then decarburized before use. This is not the same as the 12th century examples; those were of blast furnace-produced cast iron where the entire produce had to be decarburized.
Since I couldn't find any references to this in Sims later 2004 edition of Iron for the Eagles I've assumed it is still uncertain as to precicely what the structures in the Carlisle I sample were caused by (as presented in the article they were rather ambigeous about that conclusion) . Did he volunteer anything at the promised JRMES/ROMEC?
I don't know of any european historical examples of this (possibly because nobody has been looking for it - decarburization has usually been associated with post blast furnace metallurgy) but there are japanese examples of bloomery cast iron "slags" being decarburized (David Scott has a number of great articles on just that) and I seem to recall some indian examples as well.
Overall, this is a field in which, to put it mildly, more work is needed. Just as Fulford et.al. praises roman iron purity in comparison to their neighbours and successors in the article above, Godfrey and Nie (2003, JAS: "A Germanic ultrahard carbon steel punch from the Late Roman Iron Age" - an interesting article that looks at the formation of steels by carburization or low-carbon steels from blooms rather than decarburization of cast iron) concludes that "the quality of germanic ironworking could be finer than what was known in the contemporary roman world" and suggests looking for advances in iron metallurgy outside the roman empire, in the germanic areas outside the Limes. Neither conclusion seem, to me, especially solid: the comparative material in both articles is simply too weak, as is the question as to how representative the samples examined really are. Archaeometallurgy will just have to soldier on with the empirical work; jumping to conclusions can go every which way.
