Investigating the mechanical behaviour of the lining system for Raphael's Cartoon “The School of Athens”

Lining of canvases and paper artworks is a diffused conservation methodology developed to ensure the safe and long-term preservation of weakened supports. Lining systems are generally constituted by a new supporting material or a package of new materials glued to the original artefact. This paper reports on the study of the mechanical behaviour of four multi-layered paper and canvas composites, proposed as lining systems for a large drawing on paper: the “School of Athens” by Raffaello Sanzio, dated 1508. This masterpiece is the 1:1 preparatory cartoon for the wall-painting in the Vatican rooms. Uniaxial tensile testing has been employed in this study to characterize both the single layer materials and the overall mechanical behaviour of the composites. The mechanical tests have been performed before and after artificial ageing with high humidity regime. The complex testing protocol allowed selecting the best performing composite for the final lining, and to assess a safety threshold in terms of stress value for the framing and display of the restored artwork in the new showcase. The results constitute a quantitative evaluation of the different systems, and therefore they can effectively support the conservators’ activity and methodological choices.