Contextualizing the Archaeometric Analysis of Roman Glass A thesis submitted to the Graduate School of the University of Cincinnati Department of Classics McMicken College of Arts and Sciences in partial fulfillment of the requirements of the degree of Master of Arts August 2015 by Christopher J. Hayward BA, BSc University of Auckland 2012 Committee: Dr. Barbara Burrell (Chair) Dr. Kathleen Lynch 1 Abstract This thesis is a review of recent archaeometric studies on glass of the Roman Empire, intended for an audience of classical archaeologists. It discusses the physical and chemical properties of glass, and the way these define both its use in ancient times and the analytical options available to us today. It also discusses Roman glass as a class of artifacts, the product of technological developments in glassmaking with their ultimate roots in the Bronze Age, and of the particular socioeconomic conditions created by Roman political dominance in the classical Mediterranean. The principal aim of this thesis is to contextualize archaeometric analyses of Roman glass in a way that will make plain, to an archaeologically trained audience that does not necessarily have a history of close involvement with archaeometric work, the importance of recent results for our understanding of the Roman world, and the potential of future studies to add to this. 2 3 Acknowledgements This thesis, like any, has been something of an ordeal. For my continued life and sanity throughout the writing process, I am eternally grateful to my family, and to friends both near and far. Particular thanks are owed to my supervisors, Barbara Burrell and Kathleen Lynch, for their unending patience, insightful comments, and keen-eyed proofreading; to my parents, Julie and Greg Hayward, for their absolute faith in my abilities; to my colleagues, Kyle Helms and Carol Hershenson, for their constant support and encouragement; and to my best friend, James Crooks, for his willingness to endure the brunt of my every breakdown, great or small. 4 Contents Section 1: General Introduction ................................................................................... 5 Section 2: Glass as a Material .................................................................................... 10 Section 3: The History of Glassworking and Roman Sources on Glass .................... 44 Section 4: Current Issues in Glass Analysis ............................................................... 97 Section 5: The Historical Importance of Glass Analyses ......................................... 151 Section 6: Conclusions ............................................................................................. 184 Glossary of Terms .................................................................................................... 192 Bibliography ............................................................................................................. 198 5 Section 1: General Introduction Archaeometry, broadly defined, is the application of analytical techniques and expertise derived from the “hard” sciences (biology, chemistry, and physics, though the term is most closely linked with chemistry) to the study of archaeological materials. Scientists have performed compositional analyses of artifacts since the earliest days of archaeology in the 18th and 19th centuries, though this early work was often without any clear direction beyond simple curiosity about the chemical makeup of different materials, which in many cases was not well established at the time. Systematic, rigorous work in the field is largely a product of the second half of the 20th century. Undoubtedly the most famous of the archaeometric methods pioneered in this period is radiocarbon dating, which for the first time allowed archaeologists to assign calendar dates to artifacts, independently of any historical records. Other well- known types of archaeometric study include compositional analysis of pottery to determine the geological source of its raw materials, and organic residue analysis to determine the contents once held by vessels. In spite of its transformational effects on the last sixty years of archaeology, archaeometry’s methods are often poorly understood by archaeologists. Archaeometrists and archaeologists attend different conferences, publish in different journals, and (especially in North American institutions, less so in Europe) are members of different university departments. This is particularly true in classical archaeology, which is more closely tied to historical and literary scholarship of Greek and Roman civilization than it is to other archaeological fields, and is doubly reluctant to embrace a “scientific” viewpoint. 6 The present work aims to review recent archaeometric studies on a single class of archaeological material, namely glass, in a single historical period, that of the Roman Empire. It breaks no new ground in archaeometry; it presents no new technique, nor any methodological improvement to an existing one. Classical archaeologists are its intended audience; an understanding of how the chemistry of glass can be related to cultural, and economic phenomena surrounding glass production is its intended effect. To this end, Roman glass will be discussed both as a material, with particular physical and chemical properties, which lend it to certain practical applications and certain types of modern analysis; and as a class of artifacts, the product of technological developments in glassmaking with their ultimate roots in the Bronze Age, and of the particular socioeconomic conditions created by Roman political dominance in the classical Mediterranean. This review is divided into six sections, sections 1 and 6 being, respectively, this introduction, and some concluding remarks. A glossary of scientific and glass-related terminology is also included, following the conclusion. Section 2, “Glass as a Material,” describes the physical and chemical properties of glass, and how they relate to its manufacture and use in ancient societies. An understanding of the basic chemistry of glass, and how this is affected by each of its main ingredients, is necessary to engage properly with the compositional analyses that are the most common application of archaeometric techniques to glass studies. The unusual molecular structure of glass is also important to understand, as it is responsible for the properties that make glass unique as a craft material in the ancient Mediterranean, as well as for some of the key practical differences between chemical analyses of glass and pottery. This section also includes descriptions of the major 7 craft techniques in use for the production of glass vessels in the ancient world, and the methods by which glass was made from its raw materials. Section 3, “The History of Glassworking and Roman Sources on Glass,” gives some of the historical context of the Roman glass industry. The Romans are remembered in the glass industry today for the revolutionary introduction and popularization of glassblowing, and the transformation of glass from a luxury good into one of the trappings of the “middle class.” As we shall see in this section, glass had been made in the Mediterranean for over a thousand years before the Roman Empire came to dominate the region, and the age of the tradition makes its sudden invigoration in the first few decades of the Imperial period all the more striking. This was not lost on our most important extant literary source for Roman glassmaking, the polymath encyclopedist Pliny the Elder, whose thoughts on the subject are also discussed here. Understanding the history of the glass industry before the Roman Empire, and of its continuation into the Byzantine period, allows us to appreciate the significance of the technological and economic changes in glass production that occurred under Roman rule, and how the questions discussed in the following section fit into the broader context of ancient glass production. Section 4, “Current Issues in Glass Analysis,” describes the basic principles of the analytical techniques most commonly applied to the study of archaeological glass today, and explains their respective advantages and applications in archaeology. These descriptions do not aim to provide in-depth critique of technological methodology, and likely contain little that will be of interest to a seasoned archaeometric researcher; they are intended to help readers from a more traditionally 8 archaeological background to engage with archaeometric issues. This section also reviews the chemical evidence that has been used in recent attempts to determine the sources of raw materials and the locations of primary production in the Roman glass industry. Work in this area largely follows the precedents set by similar analysis of pottery. However, it faces added complications due to the two-stage process of glass manufacture, whereby the fusion of raw glass from natural materials (primary production) often occurs in a completely different location to the manufacture of glass vessels from blocks or chunks of glass (secondary production). The bulk of this section focuses on the question of where most primary production took place in the Roman Empire. Section 5, “The Historical Importance of Glass Analyses,” discusses the place of archaeometry generally, and glass analyses in particular, in archaeological endeavors, and attempts to show how chemical analysis of Roman glass can contribute to more “mainstream” archaeological questions about cultural change. Archaeometry,