Understanding hammerscale: the use of high-speed film and electron microscopy
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Published
Nov 11, 2021
Abstract
Hammerscale is the product of high-temperature oxidation of iron alloys and it is particularly associated with the forging of iron. Due to its magnetic properties hammerscale is easily recovered from archaeological contexts. While most hammerscale consists of flakes of iron oxide, a small proportion consists of spheres. This paper presents the results of the microscopic examination and chemical analysis of both flake and spheroidal hammerscale from archaeological contexts as well as material recovered during experimental forging and welding. In addition, the experimental fire-welding of iron has been recorded using high-speed digital video. This demonstrates that spheroidal hammerscale is produced during forge welding. The chemical analysis of the experimental hammerscale shows that it is formed from oxidized iron with a small but significant contribution from the non-metallic inclusions in the metal.
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References
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McDonnell G 1984, ‘The study of early iron smithing residues’, in B G Scott and H Cleere (eds), Crafts of the Blacksmith (Belfast), 47–52.
McDonnell G 1986, The classification of early iron working slags, unpublished PhD thesis, University of Aston, Birmingham.
Mills A and McDonnell G 1992, The identification and analysis of the hammerscale from Burton Dassett Warwickshire (London: Ancient Monuments Laboratory Report 47/1992).
Sato J, Ohtani H and Hirano T 1995, ‘Ignition process of a heated iron block in high-pressure oxygen atmosphere’, Combustion and Flame 100, 376–383.
Sim D 1998, Beyond the Bloom (Oxford: BAR IS 725).
Simpson F G and Richmond I A 1941, ‘The Roman Fort on Hadrian’s Wall at Benwell’, Archaeologia Aeliana 19, 1–43.
Starley D 1997, The analysis of slag and other metalworking debris from Creeton Quarry, Lincs (London: Ancient Monuments Laboratory Report 99/1997).
Steinberg T A, Mulholland G P, Wilson B and Benz F J 1992, ‘The combustion of iron in high-pressure oxygen’, Combustion and Flame 89, 221–228.
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Tylecote R F 1962, Metallurgy in Archaeology (London).
Tylecote R F and Owles E 1960, ‘A second-century iron smelting site at Ashwicken, Norfolk’, Norfolk Archaeology 32, 142–162.
Unglik H 1991, ‘Observations on microscopic smithing residues from Bixby Blacksmith Shop, Barre Four Corners, USA 1824–55’, Historical Metallurgy 25, 92–98.
Bayley J, Dungworth D and Paynter S 2001, Archaeometallurgy (London: English Heritage Guidelines 2001/01).
Birosca S, Dingley D and Higginson R L 2004, ‘Microstructural and microtextural characterization of oxide scale on steel using electron backscatter diffraction’, Journal of Microscopy 213, 235–40.
Bolobov V I 2001, ‘Conditions for ignition of iron and carbon steel in oxygen’, Combustion, Explosion, and Shock Waves 37, 292–296.
Brooks H 2000, ‘Excavations at 79 Hythe Hill, Colchester 1994–5’, Essex Archaeology and History 31, 112–124.
Charles J A and Chater W J B 1978, ‘Oxygen cutting’, Metals Technology 5, 163–175.
Chen R Y and Yeun W Y D 2003, ‘Review of the high-temperature oxidation of iron and carbon steels in air or oxygen’, Oxidation of Metals 59, 433–68.
CSIRA 1952, The Blacksmith’s Craft (Salisbury).
Forster R H and Knowles W H 1910, ‘Corstopitum: report on the excavations in 1909’, Archaeologia Aeliana 6, 205–272.
Forster, R H and Knowles, W H 1913, ‘Corstopitum: report on the excavations in 1912’, Archaeologia Aeliana 9, 230–280.
Guichard V, Barral P, Beck P, Bonenfant P-P, Boyer F, Creighton J, Dhennequin L, Dominguez-Arranz A, Dufay-Flouest A, Dungworth D, Durost S, Gran-Aymerich J, Gruel K, Guillaumet J-P, Hamm G, Haselgrove C, Jouffroy-Bapicot I, Lambert G, Laszlovsky J, Lowther P, Luginbühl T, Monna F, Olmer F, Paris P, Paunier D, Petit C, Popovitch L, Richard H, Rieckhoff S, Schubert F, Szabó M, Toledo I Mur A, Urban O, Vitali D and Wiethold J 2003, ‘Un aperçu des acquis récents des recherches sur l’oppidum de Bibracte (1997–2002)’, Revue Archéologique de l’Est 52, 45–90.
Iordanova I, Surtchev M, Forcey K S and Krastev V 2000, ‘High-temperature surface oxidation of low-carbon rimming steel’, Surface and Interface Analysis 30, 158–160.
McDonnell G 1984, ‘The study of early iron smithing residues’, in B G Scott and H Cleere (eds), Crafts of the Blacksmith (Belfast), 47–52.
McDonnell G 1986, The classification of early iron working slags, unpublished PhD thesis, University of Aston, Birmingham.
Mills A and McDonnell G 1992, The identification and analysis of the hammerscale from Burton Dassett Warwickshire (London: Ancient Monuments Laboratory Report 47/1992).
Sato J, Ohtani H and Hirano T 1995, ‘Ignition process of a heated iron block in high-pressure oxygen atmosphere’, Combustion and Flame 100, 376–383.
Sim D 1998, Beyond the Bloom (Oxford: BAR IS 725).
Simpson F G and Richmond I A 1941, ‘The Roman Fort on Hadrian’s Wall at Benwell’, Archaeologia Aeliana 19, 1–43.
Starley D 1997, The analysis of slag and other metalworking debris from Creeton Quarry, Lincs (London: Ancient Monuments Laboratory Report 99/1997).
Steinberg T A, Mulholland G P, Wilson B and Benz F J 1992, ‘The combustion of iron in high-pressure oxygen’, Combustion and Flame 89, 221–228.
Steinberg T A, Kurtz J and Wilson D B 1998 ‘The solubility of oxygen in liquid iron oxide during the combustion of iron rods in high-pressure oxygen’, Combustion and Flame 113, 27–37.
Tylecote R F 1962, Metallurgy in Archaeology (London).
Tylecote R F and Owles E 1960, ‘A second-century iron smelting site at Ashwicken, Norfolk’, Norfolk Archaeology 32, 142–162.
Unglik H 1991, ‘Observations on microscopic smithing residues from Bixby Blacksmith Shop, Barre Four Corners, USA 1824–55’, Historical Metallurgy 25, 92–98.
How to Cite
Understanding hammerscale: the use of high-speed film and electron microscopy. (2021). Historical Metallurgy, 43(1), 33-46. https://www.hmsjournal.org/index.php/home/article/view/177
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