Calibration of Digital Image Analysis Protocols for Archaeological Ceramics

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With National Science Foundation support, Dr. Chandra Reedy and an interdisciplinary team of students at the University of Delaware will develop and test new procedures for using inexpensive light microscopes to better understand ceramics, one of the most archaeologically-significant classes of materials. They will modernize the technique of thin-section petrography, which uses small samples mounted on a glass slide and ground down to 30 microns thick. When examined under a microscope with polarized light, minerals in such samples are identifiable by optical properties. Thin-section petrography is used to characterize archaeological ceramics and investigate ceramic production, function, exchange, technological style, and use history. However, the technique is often marginalized because of some challenges. For example, traditional methods of obtaining quantitative data from thin sections are very time consuming, but using only qualitative data limits usefulness. Digital image analysis has potential to alleviate these problems. However, some fundamental experimental work is needed first with laboratory-prepared standards of known composition. To ensure reliability of analyses of archaeological ceramics of unknown original recipes, protocols first must be tested for accuracy with laboratory-prepared specimens having additives of known composition, size, and amount, and fired under known conditions.The primary focus of this research, then, is to calibrate protocols for analysis of digital images of thin sections viewed under a polarizing microscope. Additional experiments will use images obtained by scanning whole thin sections under low magnification. An advantage is that these images include the entire area of the thin section rather than just a single field of view as under a microscope, facilitating macrotexture studies. Some exploratory work also will involve digital images of sherds themselves, to obtain quantitative data that supplements thin-section studies. An advantage is that the time and expense of thin-section cutting, mounting, and grinding are eliminated, allowing data to be collected on even larger numbers of specimens for rapid characterization of some features of a sherd.For all three of these approaches, using laboratory-prepared specimens as known standards is crucial for development of reliable protocols. In the final phase of research the protocols will be applied to archaeological specimens that have already been well characterized by relevant comparative techniques of analysis. Applying the finished protocols to archaeological samples will allow editing, refinement, and clearer explanations where needed so that the protocols are more widely usable and reproducible.The intellectual merit of this research is that it will result in new, modernized procedures for quantitative polarized light microscopy of ceramics. The broader impact of the study is that ceramic materials are found at archaeological sites throughout the world. These materials represent objects of a wide range of functions and serve as important markers for understanding many cultural issues about the past. This research will provide the basis for new methods of analyzing and understanding these materials, so that questions about humanity's past can be explored more fully. Students from several disciplines will participate in the project to enhance their laboratory training and ability to work together across different fields while increasing their knowledge about ceramics, one of the most important cultural materials in human history.