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[8].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 cast into bowl shaped depressions or moulds[9].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
- ^ Coghlan, H.H. (1975) Notes on the Prehistoric Metallurgy of Copper and Bronze in the Old World (2nd Ed.) Oxford: OUP Muhly, J.D. Stech-Wheeler, T. and Maddin, R. (1977) ‘The Cape Gelidonya Shipwreack and the Bronze Age Metal Trade in the Eastern Mediterranean’ in JFA 4 p.353-62 Harding, A.F. (2002) ‘The Bronze Age’ in Milisauskas, S (eds) European Prehistory: A Survey New York: Kluwer p.302
- ^ Merkel, J (1986) Ancient Smelting and Casting of Copper Oxhide Ingots" in Studies in Sardinian Archaeology II: Sardinia in the Mediterranean, Balmuth, M. (ed). US: University of Michigan Press. P.256, Tylecote 1987, 195-6, Craddock, P (1995) Early Metal Mining and Production Edinburgh: EUP p.202-4