A new imaging method of fluorescence induced by multispectral UV for studying historical musical instruments coatings

In art conservation, UV luminescence is a widespread technique: traditionally, longwave UV-A lamps (365 nm-emission peaks) are used to highlight the distribution of varnishes or retouches, and some pigments such as the red lakes. Recently, a new method of luminescence has been tested, induced by a multispectral UV-Vis radiation source (11 narrow bands in the 295-405 nm range), proving that luminescence images obtained using multiple excitation bands provide a good characterization of the luminescent properties of the material. The application to historic musical instruments, where non-invasive approaches are strongly encouraged, can be surely promising: for example, for bowed instruments the detection of specific coloring materials such as madder lake can be decisive for identifying specific finishing methods adopted in violin making by the great Masters of the past. In this work, we applied the multispectral UV luminescence method to mock-ups mimicking historical coating materials for bowed instruments, focusing on madder lake identification before and after artificial aging.