The evolution of strength,elasticity and rupture behaviour of birch tar made with ‘double-pot’ techniques during tar cooking

Birch tar was the first adhesive produced by humans. Its study has consequences for our understanding of human evolution and the development of specialised craftsmanship. One of the better-documented birch tar making methods is the ‘double-pot’ technique, where two containers are used, one containing bark, the other collecting the tar. Birch tar made with double-pots has low viscosity and bad adhesive properties. To obtain a usable adhesive, it must be reduced in volume by cooking. We investigate the evolution of tar’s mechanical properties during cooking. We use lap-shear tests to investigate strength, stiffness and failure behaviour. We found that tar must be cooked for 90 min to acquire adhesive properties. When cooked for longer, strength and stiffness increase over a 30 min lasting time span. Cooking for even longer, beyond this 30 min window, produced a substance that could no longer be used as an adhesive. The implications are that tar cooking requires a high level of skill because specific signs indicating the desired properties must be recognised during the process. Tar cooking constitutes a supplementary investment in time and resources and appears to be associated with a certain degree of risk.     

The Potential of EBSD and EDS for Ceramics Investigations—Case Studies on Sherds of Pre‐Columbian Pottery

The work focuses on the potential of structural and chemical examinations by scanning electron microscopy based methods for archaeometric studies on ceramics. Achieved by a single preparation technique (polished block sections), the feasibility and benefits of electron backscatter diffraction are demonstrated as case studies using polychrome examples of pre‐Columbian pottery (Wari, Moche and Cajamarca). Elemental and phase maps allow for separate consideration of clay and temper. Identification of mineral phases and intergrowths of temper particles provide information for clarifying clay procurement and firing techniques with respect to local versus non‐local pottery to enlighten trade relations, technological transfer and shared heritage of pre‐Columbian cultures.     

Sources of lithic material procurement in Estancia La Suiza archeological locality (San Luis, Argentina)

The present study is the first step in the elaboration of a regional base of lithic resources for an area located in the northeastern San Luis province, Argentina. Within this area lies the Estancia La Suiza archeological locality, near the hills of Sierra de la Estanzuela, where prehistoric quarry workshops have been identified. The main objective of this work was to explore the use of the different raw materials by prehistoric groups. The general geological setting of the hills of Sierra de la Estanzuela is described, and a distribution of raw material in the area is proposed. The principal sources of lithic material procurement representing the archeological record were identified, and lithic types were quantified and classified. Finally, the lithic material recovered from the Estancia La Suiza 2 quarry was characterized; the results show that the artifacts correspond to the earliest stages of production.     

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