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Seeing through the layers of a masterpiece

Caption: Paolo Romano at Galleria Nazionale dell’Umbria in Perugia. He leads the Catania section of the Institute for the Science of Cultural Heritage, part of Italy’s National Research Council. Credit: Danilo Pavone (ISPC-CNR).

Leggi in italiano

In this picture I am working on an X-ray scan of the Polyptych of St. Anthony, an altarpiece by Piero Della Francesca dating from the 15th century and now in Perugia. I am using a technique called X-ray fluorescence, that projects a beam of X-rays, only a few tens of microns wide, on the surface of the painting.

The X-rays excite the atoms of the paint and get them to emit a characteristic radiation, that we analyse to create a map of the distribution of chemical elements on the canvas — and they don’t cause any damage to the painting.

X-ray fluorescence has been used since the 1980s, but for many years it was only applied to local spots. At the CNR Institute of Heritage Science we have developed the first system able to scan large paintings continuously in a single session, working at a pace of 100 mm per second. At the Museo Capodimonte in Naples we scanned Caravaggio’s The Flagellation of Christ, that measures six square meters, in just two days.

The information we provide helps conservation specialists, who can understand where and why a painting is deteriorating. Art historians use it to study the evolution of painting techniques and to reconstruct artists’ creative process. With the Caravaggio for example, we could see how the artist tried things and changed his mind along the way, things that were invisible under normal light. We can also reconstruct the history of different restorations, because we can recognize original pigments from those that were added in the eighteenth or twentieth century.

We output the image in real time, so the museum staff do not need to wait for us to go back to the lab and process the data. Another key advantage of our system is that it is a mobile lab. There is no need to move the work of art out of the museum, which is often an obstacle.

I am a physicist, and I graduated from the University of Catania with a thesis on nuclear physics. After working on several particle physics experiments, I won a PhD grant for developing technologies for cultural heritage. I was attracted to it because I had a passion for archaeology and art, but I took a big chance. It was 1996 and those techniques were still in their infancy.

Now we have a cutting-edge X-ray laboratory in Catania, that is part of E-RIHS, the European infrastructure on heritage science. We grant access to all users for free, based on a competitive call that is issued twice per year. Our next big project, in September, will be the study of the decorations on the Tomb of Philip II of Macedon near Thessaloniki, in Greece.


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