Unveiling Raphael's Christ Blessing: Chemical Analysis Reveals Distinctive Underdrawing Techniques and a Rare Early Use of Egyptian Blue in Renaissance Art

This article highlights how advanced chemical analysis led to groundbreaking discoveries in Christ Blessing (1505-1506), a painting attributed to Raphael and housed in the Pinacoteca Tosio Martinengo, Brescia, Italy. Through a comprehensive, noninvasive scientific investigation conducted in situ at the museum, our team identified a distinctive freehand underdrawing executed in a dry medium with a pointed tool and a rare early use of Egyptian blue in Renaissance art. Crucially, the presence of this ancient synthetic pigmentlong thought to have vanished after antiquitywas chemically confirmed in the background of the composition, where it was used alongside azurite and ultramarine blue. This marks the only documented instance of Egyptian blue in a panel painting by Raphael and its only known application in a sacred subject within his oeuvre. These findings were made possible by a suite of imaging and spot-based spectroscopic techniques, including multiband and hyperspectral imaging, reflectance transformation imaging, fiber optics reflectance spectroscopy, and both spot and scanning X-ray fluorescence spectroscopy. The integration of these methods not only offered new insights into Raphael's working practice but also demonstrated the transformative potential of chemical analysis in art historical research, enhancing our ability to study and understand complex, multilayered artworks.