Reflectance imaging spectroscopy for the study of archaeological pre-Columbian textiles

In this study, two pre-Columbian textiles belonging to the Middle Orizon and Necropolis Paracas Cultures are studied by means of reflectance imaging spectroscopy. The non-invasive analysis of artifacts is a fundamental step when investigating the constituent materials and their state of conservation in order to target subsequent sampling campaigns in specific areas. The paper aims to explore the spectral properties in the Visible NearInfrared (VNIR) and Short-Wave Infrared (SWIR) intervals and investigate the spectral correlation between the relevant identified regions of interest. Two ways of selecting relevant spectral signatures are proposed: manual selection and automatic filtering. According to these two selections, the regions of interest undergo spectral unmixing in the VNIR interval to investigate which dyes had been used as such. The hyperspectral images are then mapped according to the selected endmembers in both VNIR and SWIR intervals. Small areas that feature the usage of a peculiar black thread have been given particular attention and imaged with a macro objective. The SWIR mapping on one of the samples has helped to reveal a pattern that can be ascribed to the manufacturing processes or the burial conditions.