Short-wave infrared hyperspectral imaging for organic media classification and mapping in works of art: the case of Willi Baumeister

Hyperspectral imaging (HSI) has become an increasingly valuable non-invasive technique in heritage science, particularly for the documentation and identification of pigments. However, the classification of binding media—especially organic, natural, semi-synthetic, and synthetic —remains less explored. This study presents a workflow for the mapping of binding media using short-wave infrared (SWIR) HSI (1000–2500 nm), supported by a reference spectral library of pure binding media films. To assess the reliability of the HSI system, spectral data were compared with measurements obtained using a benchtop spectrophotometer. A tailored data pre-processing and classification pipeline was developed and applied to three paintings by the German modernist Willi Baumeister. The results demonstrate successful spatial mapping of binding media, including alkyd resin/linseed oil, polyvinyl acetate and cellulose nitrate. This research underscores both the capabilities and limitations of SWIR-HSI as a non-invasive screening method to inform targeted sampling strategies. At the same time, it complements existing knowledge and contributes to a deeper understanding of the artist’s working methods.