Uppsala's laser analysis finds an 18th-century blue in two patches of the 'L daVinci' Domitian

Researchers at Uppsala University analysed the colour pigments in a historical painting signed "L daVinci"; the findings are published in the journal Materials Today Advances.

Jakob Thyr and Tomas Edvinsson, of the Division of Solid State Physics at Uppsala University's Department of Materials Science and Engineering, used Raman spectroscopy, which uses laser light to identify chemical compounds.

The painting depicts the Roman Emperor Domitian.

Carbon black, the black pigment in the signature, has been used since antiquity.

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

The Prussian blue was identified in two places: the laurel wreath on Domitian's head, and the blue jewel on the pommel of his sword's hilt.

"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," Thyr says.

"The contrast against the background is low, and it really only becomes visible when the painting is illuminated from the right angle," Thyr says of the signature.

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.

The painting belonged to a series of 12 portraits of Roman emperors, 11 of which Titian is believed to have painted from 1536 to 1539; experts believe the 12th, the Domitian, was painted by another hand.

The series is said to have been sold from England to the Spanish Royal House and was ultimately destroyed in a fire in 1734.

The Domitian painting appeared at Christie's auction house in London in the 1920s and went unsold at the time; in 1939 it was sold at an auction in Sweden and has remained in the purchaser's family since.

When the painting was auctioned at Christie's in London in 1928 and 1929, it was attributed to the Renaissance painter Titian.

The painting's current owners discovered a signature reading "L daVinci" after inheriting the work in 1994; the signature is followed by a word read as "Pinxt", an abbreviation for the Latin "Pinxit".

Microscopically small samples from different parts of the painting were analysed to determine which pigments had been used.

The paper is Jakob Thyr et al, "Leonardo under cover: A Raman spectroscopy investigation of a historic painting", Materials Today Advances (2026), DOI 10.1016/j.mtadv.2026.100871.

X-ray examinations show signs of alterations in the laurel wreath on Domitian's head: several leaves visible on the surface of the painting do not appear in the X-ray image.

The study's authors say the case is muddled by the fact that da Vinci died in 1519, 17 to 20 years before the supposed time of completion of the series, and they raise the idea that the Domitian painting could have been the first completed, thus inspiring Titian to paint the rest.

The owners sought the assistance of the Uppsala researchers, and contact was arranged by Lars Hälldahl, who had previously worked with Jakob Thyr on similar analyses of works of art.

The earliest possible date for the Prussian blue layers, the start of the 18th century, falls about 181 years after Leonardo's death in 1519.

One of the 13 identified pigments accounts for the dating result, because the other 12 were available in Leonardo's and Titian's time.

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