Pottery Function: A Use-Alteration Perspective.

Heron, Carl

The function of pottery has long been on the agenda of ceramic analysis. Whilst it has not received as much attention as ceramic technology or provenance, a number of themes, from vessel form to performance-based characteristics and organic analysis, have been proposed. Here, Skibo develops the concept of use-alteration, defined as 'the chemical or physical changes that occur to the surface or subsurface of ceramics as a result of use'. Use-alteration encompasses attrition of ceramic surfaces, carbon deposition and the analysis of absorbed organic residues. Hitherto, each of these domains has been evolving along parallel lines. The aim of the volume is to provide a theoretical and methodological framework for understanding pottery use, initially in an ethnoarchaeological context. The community under investigation is that of Guina-ang, a village within the catchment area of the long-term Kalinga Ethnoarchaeological Project in northwestern Luzon, Philippines.

After an introductory chapter emphasizing the importance of understanding pottery use, Skibo broadens the scope of the volume via an assessment of the role of ethnoarchaeology and experimental archaeology in archaeological inference. This is a useful and well-referenced piece, particularly for those who (like myself), are daunted by the magnitude of these fields of endeavour. Having said that, the discussion, as well as the review of pottery use presented in chapter 3, remains firmly within the classic 'technomic' realm of interpretation, with only passing reference to social and ideological factors that may influence pottery use.

Chapter 4 supplies relevant information on the Kalinga Project, as well as detailing the specific tasks carried out using pottery vessels. Three main vessel forms are represented; the rice cooking vessel (ittoyom), the vegetable/meat cooking vessel (oppaya) and the water storage vessel (immosso). Vessels that fail in the use for which they were designed are re-used to roast coffee, peas, beans and chillies. However, the study presented here is focused principally upon the cooking vessels in their primary use. After carrying out a comprehensive pottery census in the village, 189 intact vessels were removed from their context of use, packaged and returned to Tucson, Arizona for analysis.

Chapter 5 describes a programme of lipid (in this specific case, free fatty acid) analysis. Although the vessels were lined with resin, vestiges of the food prepared accumulated in the permeable ceramic matrix. Extraction and quantification of individual fatty acids was undertaken and various figures display the ratios of particular fatty acids in the source food, compared with the extract from the vessels. Identification of specific foodstuffs proved difficult, although general trends, such as the presence in certain foods of more characteristic fatty acids, were discernible. Due to the wide range in fatty acid ratios within and between foodstuffs, the reliance with which unknown extracts could be matched with either source food would not appear to be great. Foods exhibit a range of individual fatty acid compositions, due to natural variation, soil type and climate. In the archaeological context, characterization is further exacerbated as a result of degradation. Routine analysis of other lipids, such as sterols, steryl esters and those present in vegetable leaf waxes may have given more favourable results, although there has been very little work undertaken beyond fatty acid analysis in archaeology. In one case, identification of a 'steroid' was able to confirm the preparation of meat in an oppaya. Undated sherds, excavated from a midden deposit, demonstrated severe depletion of unsaturated fatty acids, although this is not unexpected in an archaeological context. The discussion of fatty acid decomposition is restricted to the limited archaeological evaluation of the issue, and does not consider the abundant chemical or organic geochemical literature.

Chapter 6 draws upon lithic use wear to formulate a framework for ceramic surface attrition. Attrition on the Kalinga vessels is to be found on nine different regions of the vessel surface. The aim is to link attritional trace with specific activity. Each attrition is carefully described and thoughtfully applied, making use of clear photographs and text. Attritional traces on the exterior of each cooking vessels exhibit markedly similar traces. Many of the abrasions derive from washing and these tend to obliterate more subtle traces acquired during use. According to Skibo, the attritions on the interior are more diagnostic of the cooking regime. For example, thermal spalls (small pits in the interior ceramic surface) result when rice cooking vessels are placed in the simmer position. In situations where the remaining water in the vessel is left to evaporate as steam, moisture held in the vessel wall escapes from the interior ceramic surface causing damage. Conversely, the vegetable/meat cooking pots have numerous interior scratches resulting from the greater use of utensils to stir the contents.

Chapter 7 assesses carbon deposition. Here, Skibo introduces a novel experimental approach to determine how the heating of the vessel may result in different and diagnostic traces both on the interior (food) and exterior (soot) of the vessel. The effect of wood type and moisture content of the ceramic fabric are monitored and found to give rise to different patterns of sooting and oxidized patches. Carbon deposition is seen to be a complex phenomenon, but one that offers potentially useful information regarding specific heating regimes. However, it will not always be applicable, as some cooking practices do not involve external heat sources.

The summary chapter asserts the archaeological validity of the study. As Frederick Matson points out in the Foreword, each ceramic analyst will have to assess the utility of this approach with specific regard to their assemblage. The link between observed use-alteration and activity is not straightforward, especially from long-buried sherds where prior knowledge of the foodstuffs and method of preparation is, at best, vague. The experience with lithic use wear should serve as an enlightening precedent. To those who consider that, rather than the nature of specific utilitarian operation, it is the significance associated with the context of use and the meaning attached to vessels in their various roles, then this volume may seem indigestible fare. However, as Skibo does assure the reader, these factors should not be seen necessarily in opposition, but as complements. Clearly, maximizing the potential of the three research areas presented here will be a profitable step forward in establishing patterns of vessel use and this volume is certainly an important and attractive contribution. Without doubt, such studies also require a theoretical perspective that explores the range of social, ideological and technological factors underlying patterns in adoption and utilization of pottery containers.

CARL HERON Department of Archaeological Sciences University of Bradford