FTIR and Raman microscopy of organic binders and extraneous organic materials on painted ceremonial objects from the Highlands of Papua New Guinea

This paper presents a challenging case where organic materials in micro-sized paint samples extracted from mid-20th century ceremonial objects of the Papua New Guinea (PNG) Highlands are characterized using FTIR microscopy, with the aid of solvent extraction and pre-treatment with hydrofluoric acid (HF) targeted for micro-sized samples, as well as Raman microscopy and SEM-EDS. An eclectic range of binder classes including plant-based organic matter, animal fat, wax, natural and synthetic resin, were identified on several ceremonial objects based on spectral signatures. The tree resins detected (tigaso oil and kilt tree resin) are specific to the natural flora from the PNG Highlands. Tannin-rich charred wood forming the base substrate of different ceremonial objects was also identified. In addition, degradation products from metal soaps from both synthetic and biological sources were identified.