Evaluation of microscopy techniques and ATR-FTIR spectroscopy on textile fibres from the Vesuvian area. A pilot study on degradation processes that prevent the characterization of bast fibres

The unambiguous identification of bast fibers represents one of the main challenges for archaeologists and conservators dealing with archaeological textiles, motivated by the difficulties of their investigation through the morphological features only. Therefore, in this work, a combined approach of microscopy and spectroscopy techniques is proposed. The research aims to test FT-IR spectroscopy in Attenuated Total Reflectance (ATR) mode, as a valid tool for the characterization of archaeological fibers, as already demonstrated for the modern ones, and additionally, the application of the same technique to evaluate the effect of degradation on the molecular composition of archaeological bast fibers, that may prevent their identification. To this end, a set of archeological samples, from Pompeii and the Vesuvian area, previously investigated using morphological analyses, have been studied. The results obtained showed that the preservation state of the fibres does not make their characterization simple. To understand how the ageing process influences the IR spectra of archeological fibers, a reference collection was acquired and analyzed. Moreover, two type of selected bast fibers samples were artificially aged using a climatic chamber. The outcomes achieved confirmed that the degradation process has influenced the IR spectra of the fibers to the point of making them spectrally indistinguishable, highlighting useful information to understand the role of the degradation process in the ATR FT-IR spectra of archaeological bast fibers.