Structural Investigations on Leonardo da Vinci's Mural Painting "The Last Supper" with Terahertz FMCW and TDS Techniques

Artwork and objects of cultural heritage undergo unpreventable stress due to environmental conditions or other external influences over their often centuries-long lifetime. Such influences may leave the optically visible parts of the objects intact, while invisible damages can develop invisible under the surface and endanger the structural integrity of irreplaceable works of art. One example are frescos and mural paintings, where the mortar-based preparation layers on walls are prone to developing cracks due to constant mechanical stress on the building's structure. Non-destructive testing (NDT) by terahertz measurements can help reveal such defects and yield valuable information of the layer structure of the paintings to support the work of art historians in restoration and conservation. In this contribution, we present structural investigations, which we performed on Leonardo da Vinci's famous mural painting "The Last Supper" using terahertz FMCW and TDS measurements techniques.