AIC's 52nd Annual Meeting

Effective preservation strategies depend heavily on thorough material characterization. While recent years have witnessed significant advancements in the non-destructive identification of artists' materials in easel paintings, the technical analysis of paper-based artworks has lagged behind. This is primarily due to the unique challenges presented by paper-based art, including low analyte concentrations and the delicate nature of the substrates.

Our poster presents an ongoing research initiative aimed at addressing this gap by providing insights into the identification and degradation of green pigments found in collections of early printed and hand-colored works on paper. Our focus on green pigments is motivated by the complex conservation challenges they present, such as self-discoloration, paper substrate discoloration, and paper corrosion. Our research is also inspired by the significance of the extensive and valuable collection housed at KU Leuven's Maurits Sabbe Library. This collection offers a unique opportunity to study these pigments within authentic historic objects.

This poster presentation highlights "Nouissime Hystoriarum Omnium Repercussions" (often translated as "Supplement to Universal History") (1503) by Jacobus Philippus Bergomensis, a classic Renaissance historical chronicle renowned for its rich woodcut illustrations depicting various historical scenes and figures. Several folios featuring extensive applications of different green pigments in pictorial areas are selected for in-depth study. In the initial stage, we employ narrowband ultraviolet-visible-near infrared (UV-VIS-NIR) multispectral imaging (NBMSI) and fiber optics reflectance spectroscopy (FORS) as primary non-destructive techniques for data acquisition. The NBMSI, equipped with a 150-megapixel camera and integrated software and hardware, allows for imaging at 16 wavelengths ranging from 365 nm to 940 nm and fluorescence imaging at various combinations of illumination and filters.

Analysis of the reflectance spectra suggests that malachite is the primary pigment on these folios. However, further investigation of heavily degraded areas on folio one reveals the presence of non-malachite green pigments, potentially more prone to degradation due to their discoloration to brown and the presence of breakage in the paper substrate. Comparison to the Kremer pigment checker suggests that this is a type of green earth pigment. Notable variations in the visual appearance of folios with the same pictorial schemes and the application of this green earth pigment to the identical motif are observed. These variations are likely related to different degradation states of the pigments.

This variation in degradation states within the same object offers a unique opportunity to gain insights into the degradation of green earth pigments in historic objects. Our analysis of the reflectance spectra reveals significant changes in the optical properties of the pigments during degradation, including increased reflectivity in the NIR range and enhanced fluorescence above 590 nm when stimulated by 450 nm light. This approach holds promise for characterizing the degradation states of green earth pigments through NIR and fluorescence imaging. Further investigations are needed to confirm the pigments’ composition. Advanced methods for image analysis are under development to extract crucial chemical information. Additionally, the observed variations in degradation states on different folios provide insights into factors influencing degradation patterns, offering valuable information for preservation strategies.