1930s copy of Domenico Ghirlandaio fresco
An approach known as Thermal Quasi-Reflectography (TQR) which involves mapping an MIR radiation reflected by an object has been recently developed and used on several Italian Renaissance artworks.
The technique uses little heat to produce an X-ray of the image, which in turn helps to identify various pigments used in its production which can help to determine the age and authenticity of artistic works.
Although several other light-based techniques have been in existence for some time, this newest development is able to reveal details that previous techniques, such as near-infrared spectroscopy and thermography, have missed.
In an analysis of 15th century fresco "The Ressurrection" revealed retouches, unevenness in the painting of a shield, and changes in the painting technique of the artist, which were not previously spotted before.
"Our system easily identified old restorations in which missed gold decorations were simply repainted," lead author of the study Claudia Daffara said
"The TQR system was also much better at visualising armour on some of the subjects in the fresco."
Another study of a 1930s copy of a fresco by Domenico Ghirlandaio showed the use of cinnabar which was not visible using the other near-infrared techniques.
"For mural paintings the use of the mid-infrared regions reveals crucial details," Daffara said
"This makes TQR a promising tool for the investigation of these artworks."
Dario Ambrosini of the University of L’Aquila believes that further studies need to be done in order to identify pigments used in the paintings.
"In principle, it should work whenever we desire to differentiate surface materials," he said
Ambrosini is one of the team which undertook the study, which is made up of other members from the University of L’Aquilla and the National Institute of Optics in Florence.
"This is, to the best of our knowledge, the first time that this technique has been applied on artworks," Ambrosini added
"This novel method represents a powerful yet safe tool for artwork diagnostics."
The researchers involved in the study have published their work in a paper in the Optical Society’s (OSA) open-access journal, Optics Express.