Classification of archaeological adhesives from Eastern Europe and Urals by ATR‐FT‐IR spectroscopy and chemometric analysis

Abstract Attenuated total reflection‐Fourier transform‐infrared spectroscopy (ATR‐FT‐IR) analysis of 100 adhesive samples from different prehistoric composite artefacts, pottery, and amorphous lumps across Eastern Europe and Urals were conducted with the aim to establish a fast analytical screening method for adhesive assignment. The ATR‐FT‐IR analysis allowed the identification of major chemical components of the adhesive samples that were assigned to three main groups: birch bark tar without major additives, birch bark tar with additives, and minor/non‐birch bark tar samples. ATR‐FT‐IR spectra were further analyzed using principal component analysis (PCA)‐based discriminant analysis (DA) that allowed additional refinement of adhesive classifications. The ATR‐FT‐IR results and the DA classification were confirmed by analyzing a selection of samples with gas chromatography–mass spectrometry (GC–MS). Results demonstrate that ATR‐FT‐IR coupled with DA classification allows fast and reliable preliminary identification of the major components in archaeological adhesives and their further classification. As such it is a considerable and faster alternative to more laborious GC–MS analysis, especially in the case of very small samples.