Leonardo brought to Light: Multispectral Imaging of Drawings by Leonardo da Vinci

Famous for his paintings such as the Mona Lisa and The Last Supper, Leonardo da Vinci was the archetypal Renaissance man with an interest in physics, mathematics, architecture, anatomy, and engineering. Due to his investigative nature, he often experimented with new techniques, which sometimes unfortunately resulted in disastrous consequences, such as with the flaking paint of The Last Supper. Leonardo created hundreds of manuscripts, many of which are now housed in Windsor Library and curated and conserved by the Royal Collections Trust. Such manuscripts include anatomical drawings, blueprints of his futuristic inventions, and more. Many pages are mysterious, only containing drawings in the top half suggesting there should be more beneath: Leonardo typically filled the pages of his notebooks, sometimes with various unconnected topics all on the same sheet. In order to test this theory, and also to better understand his technique, three drawings from the Royal Collections Trust underwent multispectral imaging at UCL. This scientific imaging process involved capturing images of the drawings illuminated across the electromagnetic spectrum. As materials interact with light in a variety of ways, features that cannot usually be seen in visible light alone are suddenly revealed when illuminated in ultraviolet and infrared light. This technique was applied to the drawings to see what could be uncovered. The drawings were, firstly, the studies of the horses and a dog, in which two horses were visible in the top half of the page with the remainder of the page appearing blank, secondly, the anatomy of a bear’s foot, and finally, the study for the Virgin's arm in his famous painting The Virgin and Child with St. Anne.

The multispectral imaging of the anatomy of the bear foot enabled each layer of the drawing to be digitally removed, thereby providing a fascinating insight into how Leonardo built up his drawings. The multispectral imaging of the study of the Virgin's arm revealed an underdrawing of the outline of the arm beneath the sleeve, proving that even geniuses require direction.

The most remarkable results came from the multispectral imaging of the drawing of the horses which dramatically revealed drawings of two further horses and a dog, all completely invisible to the naked eye, which were also visible when the back of the paper was imaged. Multispectral imaging is a revolutionary technology, enabling one to see the invisible. It is appropriate that this cross-disciplinary research impacting the arts and sciences should be applied to the works of the greatest polymath.