NMR spectroscopy and micro-analytical techniques for studying the constitutive materials and the state of conservation of Tapa

In this study a multi-analytical approach has been performed to characterise the constitutive materials of an ancient painted barkcloth or Tapa. Originating from Wallis Island, Polynesia, this cloth likely served utilitarian or ceremonial purposes and is part of the Felice Junck collection at the Pigorini, Muciv museum of Rome. During a recent conservation project, some micro-samples were taken from the support, brown and black painted areas and were investigated using the complementarity of SEM-EDX, FT-IR, Raman/SERS and solid-state C NMR and H HR-MAS spectroscopy. The combination of these techniques allowed the chemical characterization of the constitutive materials, from distinguishing the lignin and cellulose content of the support to the use of organic materials including condensed tannins (catechin, anthocyanidins, alkaloids), phlobaphene and vegetal anthraquinone based Morinda genus dyes for the decorations. A primary focus was placed on an understanding of its state of conservation where data of alteration products collected, namely metal carboxylates and oxalates can serve to formulate apt restoration efforts for this specific artefact.