A luminescent fish hides a millennia-old secret

• 23 April 2024
• 3 minutes

Thanks to a special imaging technique, it was possible to discover in an 11th-century painting cycle the presence of a pigment thought to have been forgotten for hundreds of years. The image of this find, a first in Ticino, earned a research team from the Conservation and Restoration Department a distinction at the SNSF Scientific Image Competition 2024.

The image emerged from complete darkness when red light triggered an emission of infrared radiation captured by a special sensor, which returned what can for all intents and purposes look like an X-ray of a fish to the computer screen. The discovery occurred in the 11th-century wall paintings of the Church of Saints Gervasius and Protasius in Cadempino. The luminescent dots that appeared on the monitor of the research team composed of Francesca Piqué, Patrizia Moretti and Stefania Luppichini indicate the presence of Egyptian Blue - an ancient pigment, the first artificial one created by man and widely used by the Egyptians, Greeks and Romans.

The discovery made by the head of the Conservation and Restoration Department of SUPSI's Institute of Materials and Constructions and her colleagues represents the first evidence of the use of Egyptian Blue in Ticino. This opens a new line of investigation to determine whether this pigment was used in other works. It will also be important to understand how this ancient pigment, generally considered forgotten after the collapse of the Western Roman Empire, was employed to decorate the walls of this small Romanesque church in the Lugano municipality.

The insight of the team from the Department of Environment Construction and Design at SUPSI in Mendrisio was to include VIL (visible induced infrared luminescence) photography in the normal set of technical photography shots. This technique is specific for the identification of the Egyptian Blue pigment and is normally performed only on older paintings. VIL made it possible to establish its unusual presence whose responses to XRF and FT-IR investigations were not traceable to any pigment generally used by artists of the time. This noninvasive technique literally uncovered Egyptian Blue, used in a mixture with Lapis lazuli blue (a natural mineral pigment), which lit within the outlines of a fish painted on the church wall. In Christian tradition the fish is associated with the figure of Christ and is often used as a symbol and attribute of the Savior in religious painting.

The image of the fish obtained with the VIL shot earned the research team from the Department of Environment Construction and Design in Mendrisio, Italy, a prize of distinction in the SNSF Scientific Image Competition 2024: a competition designed for the best photographs and videos taken by female researchers in Switzerland.

For the jury, "This cryptic, haunting image is an original take on the picture-of-a-picture trope by focussing entirely on its subject: a millennium-old painting that comes to light in a greatly reduced form through the use of technology. Radical in its simplicity and sharp contrasts, the picture resonates in the mental space of the viewer, who cannot but try to complete it."

The SNSF Scientific Image Competition 2024
The jury's choice for the SNSF Science Image Competition 2024 highlights the many facets of research. These include a photomontage revealing what is hidden from our eyes, a video showing the delicate beauty of the brain's vascular network, a geologist mapping a majestic cave, and the oddly symmetrical chaos of an acoustics experiment.

The international jury chaired by Swiss photographer Alexander Sauer selected winners in the competition's four main categories ("Objects of study," "Women and men of science," "Locations and instuments," and "Video loops") and awarded 14 other projects with distinction, including SUPSI's "Luminescent fish."

The eighteen winning works will be exhibited at the Journées photographiques de Bienne from May 3 to 26, 2024. The awards will be presented on May 16, and SUPSI will be present at the ceremony with Professor Francesca Piqué.