Material analysis provides new clues about a possible da Vinci

The painting in question depicts the Roman Emperor Domitian. When it was auctioned at Christie’s in London in 1928 and 1929, it was attributed to the Renaissance painter Titian. Later, a signature reading “L daVinci” was discovered, followed by a word that is likely the Latin pinxit, which means “painted”.

To investigate the materials used, the owners sought the assistance of researchers at the Department of Materials Science and Engineering at Uppsala University. Jakob Thyr and Tomas Edvinsson from the Division of Solid State Physics use Raman spectroscopy to examine the chemical and structural properties of materials.

A hard-to-detect signature

Contact with the researchers was arranged by Lars Hälldahl, who had previously worked with Jakob Thyr to carry out similar analyses of works of art.

“Naturally, it was exciting to work on a piece of art that might have been created by Leonardo da Vinci. What’s more, the signature is hard to detect. The contrast against the background is low, and it really only becomes visible when the painting is illuminated from the right angle,” says Jakob Thyr.

Using Raman spectroscopy, the researchers can use laser light to identify chemical compounds. In the study, microscopically small samples from different parts of the painting were analysed to determine which pigments had been used.

Pigments provide clues about the painting’s history

In total, the researchers identified 13 pigments. Twelve of these are traditional pigments used during the Middle Ages or the Renaissance and were therefore available in the time of Leonardo da Vinci and Titian. Even the black pigment in the signature, carbon black, has been used since the age of antiquity.

This means that pigments can act as markers of time. Some have been in use for a very long time, while others began to be produced at a specific point in time.

In two areas of the painting, the researchers found Prussian blue, a synthetic pigment that was not produced until the early 18th century. Thus. these particular layers of paint cannot have been applied during the lifetime of Leonardo da Vinci or Titian.

Possible retouching

However, the presence of the younger pigment does not necessarily mean that the entire painting is younger. Older paintings have often been restored and retouched. X-ray examinations also show signs of alterations in one of the areas where Prussian blue was found: the laurel wreath on Domitian’s head. Several leaves visible on the surface of the painting do not appear in the X-ray image.

“It is very common for paintings to be retouched. So, finding new pigments in limited areas does not necessarily mean that a painting is a forgery. It may be that repairs were made or parts of the painting were touched up at a later date,” says Jakob Thyr.

The results of the material analysis alone are not enough to determine who painted the artwork. It is one of several pieces of the puzzle, alongside art historical investigations, provenance and other scientific analyses.

Materials research in art and archaeology

At the same time, the study demonstrates how analytical methods from materials science can be applied to unexpected questions. The same type of spectroscopy used to characterise modern materials can also provide information about microscopic pigment grains in a work of art that is several hundred years old.

“Materials science analyses can provide concrete answers to questions about art and archaeological artefacts. I believe this type of analysis will become increasingly common in the future,” says Jakob Thyr.

Peter Westman