Database of diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and hyperspectral imaging (HSI) spectra of pigments and dyes for historical document analysis

Characterizing pigments and dyes in historical manuscripts is challenging due to the fragility of materials, the complex composition of low-concentration elements, and sampling limitations. Consequently, complementary non-invasive analytical techniques and non-contact measurement methods are often required. This study presents the most comprehensive spectral database to date, combining diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and hyperspectral imaging (HSI) to aid in identifying pigments, dyes, and binders historically used in illuminated and decorated manuscripts. A total of 156 painting mock-ups were created using traditional techniques, incorporating variations in binders, pigment particle sizes, support types, surface roughness, and application methods. Spectral imaging was performed in the visible and near infrared (VNIR) and short-wave infrared (SWIR) regions, while DRIFTS analysis covered the middle wave infrared (MWIR) region. For DRIFTS, both contact and non-contact measurements were tested. Using the samples in the database, the influence of binder, support, and grain size on the sample spectra and color were analyzed and discussed. This database facilitates pigment and dye identification using DRIFTS or HSI data independently or in combination through data fusion, applying techniques ranging from direct spectral comparison to advanced methods such as machine learning and spectral unmixing. By making this database publicly available, the study underscores the value of DRIFTS and HSI in identifying painting materials and contributes to the preservation of historical manuscripts.