Cutting-edge spectroscopic and imaging techniques revealed the molecular interactions and material behaviors that characterized these complex paint systems, substantially advancing knowledge of Renaissance art materials and their preservation.
High-resolution X-ray Raman scattering (XRS) proved instrumental in elucidating the chemical composition of mixed-media paints, enabling clear differentiation between tempera grassa and protein-coated oil paints. Model paints prepared using historically accurate methods yielded detailed carbon speciation data collected at large-scale facilities worldwide, including ESRF (France) and SSRL (United States). Key achievements included the identification of functional group transitions, mitigation of radiation damage, and the establishment of XRS as a foundational analytical tool for the study of historical paints. The implementation of cryogenic setups further enhanced analytical precision and ensured the reliability of the results.
Complementary techniques, including scanning transmission X-ray microscopy (STXM) and advanced photoluminescence methods, provided nanoscale insights into paint layer heterogeneity. STXM analyses conducted at the SOLEIL synchrotron facility revealed pronounced chemical heterogeneity in tempera paints, uncovering oxidative processes and complex binder–pigment interactions. A dedicated Python-based pipeline was developed to process and classify spectral datasets, significantly improving analytical robustness. In parallel, deep-UV photoluminescence and multispectral luminescence microscopy enabled the spatial mapping of proteinaceous and lipid components, offering valuable insights into historical paint preparation methods. Atomic force microscopy–infrared spectroscopy (AFM-IR) further enriched understanding of paint microstructure by revealing nanoscale features such as preferential functional group orientation relative to pigment particles and the subsequent formation of lead carboxylates. Together, these advanced methodologies provided a comprehensive framework for investigating the chemical and structural organization of Renaissance paints and laid the groundwork for future research in cultural heritage preservation.
Among the historical samples analyzed using deep-UV photoluminescence, particular attention was given to a microsample taken from Madonna of the Carnation by Leonardo da Vinci (c. 1475, Bavarian State Painting Collection). Initial analyses revealed preserved chemical signatures consistent with proteinaceous materials within this oil painting, underscoring the complexity of Leonardo’s material practice. To validate these findings and examine the paint structure at higher spatial resolution, AFM-IR was employed, revealing nanoscale protein signatures localized around pigment particles and embedded within the oil binder. These results provided direct molecular-level evidence that Leonardo da Vinci prepared his paints using protein-treated pigments dispersed in an oil-based medium.
This discovery was highly significant, as it confirmed the deliberate use of mixed-media paint formulations during the transitional period from tempera to oil painting in the late fifteenth century. It offered rare insight into Leonardo’s workshop practices and demonstrated that complex protein–oil systems were intentionally engineered, likely to modulate paint properties such as stability, handling, and drying behavior.
