Non-invasive measurements of damage of frescoes paintings and icon by laser scanning vibrometer: experimental results on artificial samples and real works of art

Abstract

Frescoes and icons show analogies in terms of defects, both present layer-to-layer detachments and delaminations and surface cracks; the aim of this work is to develop a diagnostic system for the measurement of the defects’ position and size. After initial measurement set-ups based on accelerometers and impact hammers a novel system based on laser vibrometers and acoustic stimulation of structures to allow full remote and contactless investigation of detachments and delaminations has been developed. This paper presents a measurement procedure based on two subsequent scans of the work of art: the first scan aims at finding the defects’ positions, the second one characterizes their resonant response. A new kind of exciter, namely piezo actuators, has been introduced in the measurement chain and its effectiveness in finding defects in icons will be demonstrated. In situ measurements on real frescoes have been performed in Senigallia (near Ancona) and Orvieto to assess the proposed technique and a sample of the obtained results will be presented.