Plano-convex ingot
Plano-Convex ingots, also known as bun ingots, are lumps of metal, circular in plan with a flat or slightly concave top and a rounded base. They are most often made of copper although plano-convex ingots of other materials such as copper alloy[1] , lead[2] and tin[3] are also known. Their characteristic shape is formed when molten metal solidifies within a bowl shaped cavity such as a mould [4] or depression in the ground [5]. Forms of plano-convex ingot are found across a wide chronological and geographical range with the first examples known from the Near East during the 3rd and 2nd Millennia BC . By the end of the Bronze Age they were found widely from North West Europe to South Asia[6] and similar ingot forms continue in use during later Roman and Medieval periods[7]
Manufacture
In the past plano-convex ingots have been seen as a primary product of smelting, formed at the base of a furnace beneath a layer of less dense slag .However experimental evidence has shown that regularly shaped plano-convex ingots are difficult to form within the furnace and many plano-convex ingots may have been formed outside of the smelting furnace being tapped or remelted in crucibles and cast into bowl shaped depressions or moulds.The composition and structure of the metal within some plano-convex ingots suggests that it may derive from secondary processes such as refining, alloying or the recycling of scrap metal rather than smelting.
References
- ^ Bass, G.F. (1967) Cape Gelidonya: A Bronze Age Shipwreck US: American Philosophical Society, Maddin, R. & Merkel, J. (1990) ‘Metallographic and statistical analyses’ in Lo Schiavo, F Maddin, R Merkel, J. Muhly, J. D. & Stech, T (eds) Metallographic and statistical analyses of copper ingots from Sardinia P.42-199. Ozieri: Il Torchietto
- ^ Waschmann, S. (2009) Seagoing Ships and Seamanship in the Bronze Age Levant (2nd Ed) US: Texas A&M University Press
- ^ Tylecote, R.F. (1987) The Early History of Metallurgy in Europe. London: Longman, p.204 Pulak, C (1998) ‘The Uluburun Ship: An Overview’ IJNA 27 (3) p199
- ^ Pulak 1998, 196
- ^ Weisgerber, G. and Yule, P (2003) ‘Al Aqir near Bahla – an Early Bronze Age Dam Site with Plano Convex Ingots’ in Arabian Archaeology and Epigraphy 14 p.48
- ^ Tylecote 1987, 194-209, Janzon, G.O. (1988) ‘Early Nonferrous Metallurgy in Sweden’ In Maddin, R. (ed) The Beginning of theUse of Metals and Alloys US: MIT Press p.104-17, Piggott, V.C. (ed) (1999) The Archaeometallurgy of the Asian Old World :MASCA Research Papers, Begemann, F., Schmitt-Strecker, S. Pernicka, E., and LoSchiavo, F. (2001) ‘Chemical Composition and Lead Isotopy of Copper and Bronze from Nuragic Sardinia’ in EJA 4 p43-85, Hauptmann, A., Maddin, R. and Prange, M. (2002) ‘On the Structure and Composition of Copper and Tin Ingots Excavated from the Shipwreck of Uluburun’ in BASOR 328 p.1-30, Weisgerber and Yule 2003, 48-9
- ^ Whittick, G C, & Smythe, J A 1937 'An examination of Roman copper from Wigtownshire and north Wales', Proc Univ Durham Phil Soc, 9/2 (1937), 99-104. Andre, P. (1976) ‘A Copper Ingot From Brittany’ in Bull. Board Celtic Studies 27 p148-53 Tylecote 1987, 202-6