Multi-technique tribosystem and wear mechanics analysis of bipolar flaking: Integrating 3D digital, 3D profilometer, and scanning electron microscopy – Experimental and archaeological material analysis from the site of La Cansaladeta (MIS11; Tarragona, Spain)

The bipolar technique has long been a subject of extensive experimental research. Studies conducted to date have characterized it in various ways: some emphasize its simple technological structure, while others highlight its utility as a practical approach. Despite these differing assessments, one fact remains clear: bipolar technology has been recognized across different times and places, without restriction to a specific chronology or geography. In this study, we aim to approach the concept of wear mechanics in the bipolar technique from a tribological perspective. Specifically, our research focuses on understanding the wear mechanisms inherent to the bipolar method. From a tribological perspective, the bipolar technique is particularly significant at two points: the percussive contact (between the core and the hammerstone) and the sliding contact (between the core and the anvil). The main focus of this study is the quantitative and qualitative analysis of abrasive traces formed at the sliding contact, which is a characteristic feature of this technique. Additionally, we examined refit sets from the La Cansaladeta site (MIS11; Tarragona, Spain) to analyze the micro-characteristics of the bipolar technique from a tribological perspective. The preliminary results involving materials such as K9 crystal and obsidian raw materials that came into contact with the anvil exhibit a high density of linear traces. In contrast, such traces were not observed as intensively on quartzite raw materials. In the archaeological refit sets, linear traces attributable to friction were identified; however, these traces do not appear to result from sliding on the anvil. Instead, they are more likely the product of natural processes. This interpretation is supported by the fact that the traces occur not on fresh fracture surfaces, but rather on cortical areas. Our study employed a multi-technique, multi-scale approach using 3D digital microscopy, scanning electron microscopy, and 3D optical profilometry. This approach not only provided insights into the micro-characteristics of the technique but also prompted a re-think of certain aspects of wear, particularly the formation of linear features. From a quantitative perspective, our results allowed us to assess how the formation mechanisms of linear traces influence quantitative data. Overall, our findings demonstrate that quantitative and qualitative trace analyses are complementary, and that quantitative analysis is most meaningful when grounded in qualitative observations.