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The chemical composition of the flint insert and the black adhesive layer on it and of the adhesive lump found from the Early Mesolithic Pulli settlement site was determined by the attenuated total reflectance Fourier transform infrared(ATR-FT-IR)spectroscopy. The black adhesive lump and layer on the artefact is birch bark tar probably mixed with some fat and possibly containing some coniferous tree resin.
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Vahur et al. (2011) studied this question.
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