Xeroradiography: A key to the nature of technological change in ancient ceramic production

Abstract

Over the last two decades Industry and Medicine have developed and fully exploited various X-ray techniques, especially xeroradiography. It is only recently, however, that the latter has found significant use in museum-related disciplines, the appeal being that it is nondestructive in its usual mode of application. Though the production of xeroradiographic images has been largely constrained to situations where the X-ray beam incidence is normal to the object's surface — we will illustrate that information recovery is not optimized in that configuration — some valuable data has been gleaned about certain characteristic features of ceramic structure. For example, the frequency, grain structure and gross aspects of rock and mineral inclusions are often radiographically distinct, when their effective atomic number is significantly different from the surrounding clay matrix. (Haematite, muscovite and calcite show up particularly clearly.) Similarly, remnants of organic matter, such as any rice or straw temper that the potter may have added, produce quite distinct images. We have now adapted routine xeroradiographic methods to accurately reconstruct the method of manufacture of individual pottery vessel types from a wide range of past cultural horizons. Adjustments in X-ray exposure settings and angles of incidence, coupled to an internal study of certain vessel forms (using a “thick section” technique that we will describe in detail), has allowed us to identify subtle changes with time in ancient pottery production methods, and has prompted much reassessment of current ideas about technological innovation within several cultures, including those of Bronze Age Jordan and prehistoric Thailand. This paper will summarize the technical aspects of these changes, and consider the past social conditions which may have stimulated them.