EXPERIMENTS CONCERNING THE MOLD MATERIALS USED IN THE PRODUCTION OF THE COPPER INGOTS FROM THE LATE BRONZE AGE SHIPWRECK EXCAVATED AT ULUBURUN, TURKEY A Thesis by THOMAS SCOTT LARSON Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF ARTS August 2009 Major Subject: Anthropology EXPERIMENTS CONCERNING THE MOLD MATERIALS USED IN THE PRODUCTION OF THE COPPER INGOTS FROM THE LATE BRONZE AGE SHIPWRECK EXCAVATED AT ULUBURUN, TURKEY A Thesis by THOMAS SCOTT LARSON Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF ARTS Approved by: Chair of Committee, Cemal Pulak Committee Members, Shelly Wachsmann Angie Hill-Price Head of Department, Donny Hamilton August 2009 Major Subject: Anthropology iii ABSTRACT Experiments Concerning the Mold Materials Used in the Production of the Copper Ingots from the Late Bronze Age Shipwreck Excavated at Uluburun, Turkey. (August 2009) Thomas Scott Larson, B.A., University of San Diego Chair of Advisory Committee: Dr. Cemal Pulak Underwater excavations of a Late Bronze Age shipwreck at Uluburun, Turkey recovered a combined 475 oxhide and plano-convex discoid copper ingots. While the hoard of ingots excavated at Uluburun brings the total number of copper ingots from the Late Bronze Age to over 1000, interestingly, only one ingot mold from the that period has been identified. Scholars have speculated over the means behind the creation of these ingots for decades, but with a relative absence of archaeological molds the most promising method of reaching any conclusions as to the types of molds used in antiquity seems to be experimentation. Experimental archaeology, has, in recent years been responsible for many breakthroughs in how the past is viewed. In the face of an overwhelming disparity of copper ingot molds from the Late Bronze Age, trials designed around testing different mold materials and casting techniques have the potential to determine, with relative certainty, how copper ingots were cast over 3000 years ago. iv This thesis examines the possible materials used to create copper ingot molds through a study of their prevalence in antiquity and also details experiments in which these materials were used, in concert with different casting techniques, to create copper ingots. The results of these experiments are combined with analyses of the Uluburun ingots in an effort to bring some closure to the debate surrounding copper ingot molds in the Late Bronze Age. v DEDICATION For my wife, the beautiful Dr. Heather Larson vi ACKNOWLEDGEMENTS Now that this project is at an end, and I have time to give pause and reflect on it, I realize that there are far too many people, other than me, responsible for its completion. Only with their contributions would these experiments have been possible. With only these scarce few lines to give thanks and acknowledge their assistance and support, I am sure I will leave someone out. So, I apologize in advance for any people I may forget in the following paragraphs. Even though words cannot express the debt of gratitude I feel for her unyielding support and companionship since the day we met, I must thank my wife, Heather. Without her, I am quite certain these words would have never been written. Professionally, I cannot thank Dr. Cemal Pulak enough for first taking a chance on me and allowing me to handle the Uluburun ingots for two summers in Turkey and then deeming me worthy to take on a thesis examining their production. Thank you, Cemal. I am forever in your debt. You guided me through this and this thesis is yours as much as it is mine. Dr. Angie Hill-Price, thank you for taking on a student with a project outside the traditional realm of Manufacturing and Mechanical Engineering Technology. Without your assistance both in the analysis of my samples and their processing, this project would have most certainly stalled out. Jim Jobling, thank you for helping me build and later store an unstable and dangerously hot-burning furnace on the grounds of the Conservation Research vii Laboratory at the Riverside campus of Texas A&M. I am sorry for the mess I left behind. To the Kennecott Utah Copper Corporation, thank you for providing me with enough impure copper to conduct these experiments. Finally, I would like to thank the faculty, staff and students in the Anthropology Department at Texas A&M during my time in College Station. You made a kid from the west coast feel at home, deep in the heart of Texas. viii TABLE OF CONTENTS Page ABSTRACT…………………………………………………………………………..... iii DEDICATION…………………………………………………………………………... v ACKNOWLEDGEMENTS…………………………………………………………….. vi TABLE OF CONTENTS……………………………………………………………... viii LIST OF FIGURES…………………………………………………………………....... x LIST OF TABLES…………………………………………………………………….. xii CHAPTER I INTRODUCTION……………………………………………………… 1 The Copper Ingots from the Uluburun Shipwreck……………… 2 Physical Appearance of the Uluburun Ingots…………………… 5 Experimental Archaeology in Casting Copper Ingots…………... 9 II LITERATURE REVIEW…………………………………………….... 11 Copper Ingots from the Late Bronze Age……………………… 11 Previous Experimentation……………………………………… 14 Clay Molds……………………………………………………... 20 Refractory Materials………………………………………….... 26 Stone Molds…………………………………………………..... 29 Sand Molds…………………………………………………...... 34 III EXPERIMENTATION………………………………………………… 36 Copper Used………………………………………………….... 36 Furnace and Fuel……………………………………………….. 37 Molds…………………………………………………………... 42 IV CASTING EXPERIMENTAL INGOTS……………...……………….. 48 Casting of the Ingots…………………………………………… 48 ix CHAPTER Page Single Pour Ingots……………………………………………… 51 Sand Mold, Single Pour………………........................... 51 Macroscopic Observations……………………... 51 Microscopic Observations……………………... 53 Limestone Mold, Single Pour…………......................... 57 Macroscopic Observations……………………... 57 Microscopic Observations……………………... 61 Clay Mold, Single Pour #1…………………………….. 63 Macroscopic Observations……………………... 63 Microscopic Observations……………………... 70 Clay Mold, Single Pour #2…………………………….. 74 Macroscopic Observations……………………... 74 Microscopic Observations……………………... 76 Double Pour Ingots…………………………………………….. 80 Limestone Mold, Double Pour: Hot…………………… 80 Macroscopic Observations……………………... 80 Microscopic Observations……………………... 86 Limestone Mold, Double Pour: Cold…………………... 90 Macroscopic Observations……………………... 90 Microscopic Observations……………………... 93 Sand Mold, Double Pour: Hot………………………..... 99 Macroscopic Observations……………………... 99 Microscopic Observations……………………. 102 Sand Mold, Double Pour: Cold………………………. 103 Macroscopic Observations……………………. 103 Microscopic Observations……………………. 106 Clay Mold, Double Pour: Hot………………………… 107 Macroscopic Observations……………………. 107 Microscopic Observations……………………. 110 V DISCUSSION AND CONCLUSIONS………………………………. 115 REFERENCES……...………………………………………………………............... 134 APPENDIX A………………………………………………………………………… 140 APPENDIX B………..……………………………………………………………….. 141 VITA………………………………………………………………………………….. 144 x LIST OF FIGURES FIGURE Page 1 The scratch-built furnace used for these experiments…………………. 39 2 Furnace with crucible prior to removal of molten copper……………... 40 3 Clay mold after the casting of the first ingot…………………………... 43 4 The author carving the limestone mold with a pneumatic chisel…..….. 45 5 Limestone mold, split from thermal sh ock during the casting of the copper ingot……………………………………………………………. 46 6 Green sand mold prior to the pouring of molten copper……………..… 47 7 Pouring molten copper from the crucible into a sand mold….………… 49 8 Directionality within the sand mold, single-pour ingot at 200x magnification………………………………………………………….... 54 9 Sand mold, single-pour ingot at 200x magnification ………….………. 56 10 Limestone mold, single-pour ingot at 200x magnification…………….. 62 11 Fragments of clay from mold embedded in the center and upper right of the ingot………...……………………………………………... 65 12 Finger impressions on the clay cast ingot imparted from the clay mold…………………………………………………………………….. 67 13 Magnified view of clay inclusion in the first single-pour ingot cast in the clay mold………………………………………………………… 71 14 Clay mold, single-pour at 200x magnification…………...…..……....… 73 15 Porosity within the second clay mold, single-pour ingot at 200x magnification…………........................................................................... 77 16 Second clay mold, single-pour ingot at 200x magnification …….…….. 79 xi FIGURE Page 17 The formation of a volcano-like gas blister on the edge of an ingot cast in a limestone mold……………………………………………….. 82 18 The solidified gas blister on the surface of the ingot after cooling completely……………………………………………………... 83 19 Grain details of the limestone mold, hot double-pour ingot at 200x magnification……………………………………………………….….. 87 20 Limestone mold, hot double-pour ingot at 200x magnification…….….. 89 21 Limestone mold, cold double-pour ingot………………………….…… 92 22 Grain details of the limestone mold, cold double-pour ingot at 200x magnification…..………………………………………………………. 95 23 Limestone mold, cold double-pour ingot at 200x magnification…....…. 98 24 Grain structure of the clay mold, hot double-pour ingot at 200x magnification…………………………………………………………. 111 25 Clay mold, hot double-pour ingot at 200x magnification……………... 120 26 Grain structure of the single-pour ingot cast in a clay mold……..….… 123 27 Grain structure of an Uluburun ingot……………………………….…. 124 28 A corner projection of an Uluburun oxhide ingot suggesting that