Dating of a unique six-colour relief print by historical and archaeometric methods

The aim of this work is the historical and archaeometric investigation of a unique six-colour single-sheet relief print on paper belonging to a private collector. It is undescribed, undated and unsigned, and it depicts Charlemagne enthroned in Aachen Cathedral. The print was tentatively dated to the 16th century based on the style and iconography. This study offers a revised dating based on stylistic analysis of the design and archaeometric investigation of the six printing inks. The methodology consists of the complementary use of imaging and spectroscopic techniques, which are entirely non-invasive and non-destructive due to the rarity and fragility of the object. In particular, preliminary unaided visual analysis, UV fluorescence and IR reflectography were used to investigate the surface condition of the impression and to select the most promising areas for further analysis. Raman spectroscopy and XRF were used to identify pigments and treatments. Our results show that the paper support is in good condition. The pigments of all six inks have been identified. Results suggest that this impression was printed after 1850 and before 1900. In its conception and production, this artwork used then-modern methods and materials to pay homage to the styles and production techniques of the earliest German colour woodcuts.