An Examination of Deterioration Products Found on Tin Ingots Excavated from the 14 th Century B.C., Late Bronze Age Ship
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An Examination of Deterioration Products Found on Tin Ingots Excavated from the 14th Century B.C., Late Bronze Age Shipwreck, The Ulu Burun, Near Kas, Turkey. Laura Lipcsei1, Alison Murray2, Reginald Smith3, and Mahmut Savas4. 1, 2
Art Conservation Program, Department of Art, Queen’s University, Kingston. Department of Materials and Metallurgical Engineering, Queen’s University, Kingston. 4 Department of Mechanical Engineering Department, Bogazici University, Istanbul. 3
ABSTRACT The purpose of this study was to investigate the deterioration of tin ingots recovered from a late 14th century B.C. (Late Bronze Age) shipwreck off Ulu Burun (Kas) Turkey. As so little elemental tin has been excavated from underwater sites and preserved to date, the Ulu Burun ingots offer a unique opportunity to study the degradation products of ancient tin artifacts from a natural marine environment. The current investigation had three major objectives: to identify corrosion products; to confirm or refute the presence of ‘tin pest’, which has been asserted as one of the major reasons for the disintegration of the ingots and a topic of much controversy in the conservation and museum communities; and, finally, to contribute to the overall understanding of marine tin. The following instrumental techniques were used to analyze ingot samples: x-ray diffraction, atomic absorption, inductively coupled plasma emission spectroscopy. The results of the analysis have identified corrosion products that are characteristic of the type of products anticipated on tin objects from a marine environment. The presence of the controversial tin pest disease was confirmed in two of the six samples tested. Sample preparation appears to be a potential factor in the determination of tin pest using XRD. INTRODUCTION More than 40 tin ingots and numerous fragments, totaling nearly one ton of metal, were excavated from the 14th century B.C. Late Bronze Age shipwreck at Ulu Burun, (Kas) Turkey between 1984 and 1994 by the Institute of Nautical Archaeology (INA) at Texas A & M University [1, 2]. The ingots were excavated from a sunken shipwreck located 60 to 70 metres off the east face of cape Ulu Burun and 400 metres from its tip. The wreck is on a steep rocky slope at a depth of between 44 and 52 metres. The objects themselves were deposited as deep as 61 metres [2]. The Ulu Burun ingots, now at the Bodrum Museum of Underwater Archaeology, show varying degrees of preservation ranging from solid ingots completely covered with hard, insoluble corrosion products, to ingots reduced to piles of a soft blue-grey powder. Most of the samples for this study were taken from the so-called “ox-hide” ingots, i.e. rectangular ingots with a handle-like protrusion at each of the four corners, a shape which early excavators once thought resembled those of flayed ox skins [1]. The average size of the ingots can be extrapolated from intact, wellpreserved specimens, such as tin ingot KW1932, which measures approximately 62.5 cm in length, 31 cm in width, and 4.5 cm thick, and weighs 23
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