The chemical analysis of archaeological residues can offer valuable insights into the technical complexity of ancient hominins, thus opening a window to their cognitive complexity and socio-economic exchange networks. The scarcity of residue findings in the archaeological record
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The chemical analysis of archaeological residues can offer valuable insights into the technical complexity of ancient hominins, thus opening a window to their cognitive complexity and socio-economic exchange networks. The scarcity of residue findings in the archaeological record bears the need for non-destructive analytical tools. Various combinations of non-destructive techniques, for instance optical microscopy, infrared or Raman spectroscopy, have been implemented. These techniques are also often combined with destructive GC-MS analysis, which is the most common analytical method for these organic materials. However, currently, there is no systematic proposed way to analyse archaeological residues non-destructively. This project aims to verify the organic nature and test the reliability of identification of archaeological adhesive materials with a combination of non-destructive methods. For this purpose, SEM-EDS, FTIR microspectroscopy in reflectance mode, Raman microspectroscopy and XRD are implemented. A set of experimental adhesive replicas of pure materials and mixtures are examined in pristine form, but also after a three-year-long weathering experiment. The materials tested are pine tar, birch tar, pine resin, beeswax and mixtures of pine resin with beeswax, as well as pine resin with beeswax and ochre; these materials are representative for archaeological finds. Additionally, a set of archaeological samples were studied, consisting of Mesolithic bone/antler points with adhering hafting adhesive residues, form the Dutch North Sea. This research shows that the effectiveness of each method varies with the different materials and mixtures tested. In addition, degradation negatively influences the reliable verification and identification of the organic residue constituents significantly. A single method is usually unable to reliably identify weathered and degraded samples, creating the need for consideration of combined results from multiple methods. A protocol is eventually proposed for the systematic non-destructive analysis of unknown archaeological residues, based on the observations of this research. The protocol recommends SEM-EDS as a starting point of analysis for verifying the residue’s organic nature. The combination of micro-FTIR and micro-Raman follows, to reinforce the verification of organic matter and identify the residue constituents. Lastly, XRD can identify additives to the residue mixture and phases related to the artefact’s environment of burial.