In order to investigate archaeological materials from the Tsaghkahovit Plain from a variety of structural scales, Project ArAGATS researchers have developed formal protocols for the digital radiographic (DR) and X-ray computed tomographic (XCT) examination of archaeological ceramics and metals at Argonne National Laboratory’s (ANL) non-destructive evaluation (NDE) group. Previous applications of X-ray imagery in archaeology have focused on the use of analog (film) radiographic imaging methods to assess internal, macro-scale structural features of archaeological materials like ceramic vessels and human skeletons. We have concentrated on two newer applications of X-ray radiography to ceramic (and to some extent metallic) archaeological materials which produce imagery at the macro-, meso-, and micro-scales.
Direct radiographic techniques, similar to those used in traditional medicine, have been particularly relevant in archaeology as a way to discern different techniques for the formation of ceramic vessels, as well as segmented metal objects exhibiting welds and other joins. In order to take full advantage of newer digital imaging capabilities some adjustments in technique from older analog procedures are needed, due to the differing means utilized by the image sensors for detecting energies from the X-ray source. Whereas analogue film techniques involved the “soaking” of objects in the X-ray beam for long periods of time, digital techniques take only seconds, but require generally stronger levels of energy to produce the ideal image. The overall benefit is generating high quality digital images which can be post-processed, manipulated, and compared to one another in a standardized fashion, using specialized software also developed by the project. ANL’s XCT facility provides the X-ray source, detector, and image acquisition software for this effort. The DR protocols developed by the project represent an essential transition from analog to digital radiographic imaging methods through the development of highly vetted standards and procedures for the analysis of archaeological ceramics.
During this initial period of protocol development, project researchers analyzed hundreds of sherds from the Bronze and Iron age occupations of the Tsaghkahovit Plain as well as experimental vessels fired in Yerevan, Armenia during the summer of 2006. The ancient ceramics were used to generate experimental images to isolate the most appropriate operating parameters for edge definition and image clarity. Ceramic materials from Early Bronze Age Azerbaijan, previously analyzed with analog radiographic techniques by Mary Fran Heinsch and Pamela Vandiver, were used as comparative samples in order to hone settings and procedures. Ongoing research marshals the DR of pottery to examine production techniques stretching from the Neolithic to the first millennium BC.
X-ray computed tomography, known as CT in the medical community, is a significantly newer radiographic technique, available only since the advent of digital imaging methods, and permits the full volume, 3D imaging of archaeological materials. The value of such imagery is twofold. First, full-volume XCT images provide a quantitative and therefore statistically comparable dataset of both internal and external object structure and variation. Secondly, analytical software constructed with IDL imagery vocabulary makes it possible to split, splice, and slice object volumes into an almost infinite series of subsections and segments, providing access to different object internal structures. This was previously impossible without irreparable destruction of the object. XCT technique development is ongoing and will likely be fully deployed in Project ArAGATS analyses by 2013.