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Multispectral Imaging of Leonardo da Vinci Drawings

Cerys RJones16 June 2019

In the first year of my PhD, I was asked by Alan Donnithorne, the former head of conservation of prints for the Royal Collection Trust, whether I would be interested in capturing multispectral images of three Leonardo drawings for a book he was writing. Of course I eagerly agreed and in July 2016 Alan brought three beautiful studies by Leonardo to UCL ready for imaging.

The first drawing was the ‘Studies of horses and horses’ heads’ created circa 1481. This is a metalpoint drawing of the portrait of a horse’s head and another in side-profile. To create a metalpoint drawing, a metal-nibbed stylus is used to engrave lines onto paper that has been prepped with glue and ground animal bone, whilst also leaving a deposit of the metal. Although only two horses heads could be seen in visible light, when illuminated in ultraviolet light, two more horses and a dog appeared at the bottom of the page that were invisible to the human eye.

‘Studies of horses and horses’ heads’ illuminated under visible light (left) and after multispectral imaging (right). The two horses and dog at the bottom of the page cannot be seen using the human eye alone. (Image copyright: Queen Elizabeth II, Moral rights: Cerys Jones)

The second drawing was of ‘the anatomy of a bear’s foot’, circa 1488-90. Leonardo initially studied anatomy to inform his paintings;however,this eventually evolved into a plan to write a never-completed treatise on the subject. Martin Clayton, in his 2019 book Leonardo da Vinci: a life in drawing, explained how, at the time, human dissection was illegal and so Leonardo may have been interested in the bear’s foot due to the similarity in the way humans and bears walk. The multispectral imaging of this drawing enabled the different materials (metalpoint, pen and ink, and white heightening) to be separated and show how Leonardo built up his compositions.

The final drawing was a study for ‘the drapery of the Madonna’s arm’ (c. 1510-1515) created for ‘the Madonna and Child with St Anne and a lamb’, a painting currently in the Louvre Museum in Paris. The multispectral imaging revealed the outline of the arm under the drapery,implying that Leonardo first drew a template for the arm and then built the drapery on top of that . The images also enhanced the different materials, including black and red chalk, pen and ink, brush and ink, and white opaque watercolour.

Capturing the multispectral images of the study for ‘the drapery of the Madonna’s arm’. (Image: Cerys Jones)

The full results from this imaging are in Alan’s book Leonardo da Vinci: A Closer Look. This fascinating book investigates many of the Leonardo da Vinci drawings held in the collection at Windsor Library, using a variety of imaging techniques, including multispectral imaging, microscopy, X-Ray fluorescence, and more. He shows Leonardo’s drawings in a way never seen before—including these features invisible to the human eye—to present a detailed view of Leonardo’s musings and thoughtful mind.

The studies for ‘the anatomy of the bear foot’ and ‘the drapery of the Madonna’s arm’ are currently on display in the Queen’s gallery as part of the new exhibition Leonardo da Vinci: a life in drawing to commemorate the 500-year anniversary of Leonardo’s death. This exhibition displays over 200 drawings from Leonardo’s life, spanning a range of topics including anatomy, optics, engineering, botany, cartography and more. I was honoured to be invited to a private view of the exhibition before it was open to the public to celebrate Leonardo’s work and the release of the book. The exhibition is captivating and provides a fascinating insight into Leonardo’s mind, which you can see jumping across subjects on a single piece of paper. I encourage everyone to attend and be inspired by Leonardo’s inquisitive and ingenious mind.

If you’re interested in learning more about my work on the Leonardo drawings, check out my poster!

At the private view of the Leonardo da Vinci: a life in drawing exhibition at the Queens Gallery in Buckingham Palace (Image: Cerys Jones)

The Invisible Glow of Egyptian Blue

Cerys RJones20 July 2018

If you were to visit the Petrie Museum with infrared vision, you would probably be drawn to wildly different parts of the collection than you would normally. Certain artefacts would appear to glow before your eyes. This is because of the inventively-named pigment Egyptian blue, which, as the name tells you, is a blue pigment that was commonly used in Egypt. However, Egyptian blue has a special property that makes it stand out from the rest: when illuminated in visible light, it fluoresces infrared light. If you could see infrared light, you would see all of the artefacts that contain this pigment glowing. I haven’t yet evolved to have this special power, but I have a camera that does. This is a multispectral imaging system and is what my PhD research is focused on. Multispectral imaging involves capturing images of objects that are illuminated in ultraviolet, visible and infrared light to reveal features that cannot be detected by the human eye alone.

Last November, I captured multispectral images of this Egyptian mummy mask from the Petrie Museum. In the Petrie catalogue, it is described as a “linen-based cartonnage mask, painted with blue headcloth, white face, black brows, eye-borders and pupils, and red-edged yellow band around face.” This mummy mask would have placed over the mummified body to protect the deceased in the afterlife. The Petrie has several mummy masks in the collection, including some that are gilded with gold.

Late period cartonnage mask (Petrie Museum, 55084)

The mask was illuminated in visible light and an infrared filter was placed in front of the camera lens. This meant that only infrared light was able to pass through the lens and be captured by the camera. The resulting image is below. The blue headcloth appears brightly in the image, indicating that it is painted in Egyptian blue. We were also able to confirm that the little fragment of mask in the vial was also from the headpiece, as this also fluoresced.

The cartonnage mask illuminated in visible light (left) and captured with an infrared filter (right). (Photo: Cerys Jones)

When you search Egyptian blue in the Petrie catalogue, 194 results appear ranging from Egyptian blue scarab beetles to plaster with hieroglyphs written in Egyptian blue paint. Two of my favourite items from the collection are the Egyptian blue hippopotamus and the Egyptian blue paste amulet of a lion-headed goddess. The hippopotamus represents Taweret, the Ancient Egyptian goddess of childbirth and fertility. The lion-headed goddess is probably Bastet, the goddess of warfare in Lower Egypt .

Left, hippopotamus in Egyptian blue pigment (Petrie Museum, 6489) and right, Egyptian blue paste lion-headed amulet (Petrie Museum, 52875).

Next time you visit an Egyptian museum, keep your eyes out for any artefacts that are painted in Egyptian Blue that are glowing unbeknown to your eyes!