An Integrated Approach to the Study and Preservation of Paintings Using Laser Light Technology: Diagnosis, Analysis and Cleaning
Paintings are particularly sensitive and fragile, mainly due to their complexity in materials and structures and their susceptibility to environmental conditions. In this context, the nature and properties of laser light allow for accurate and sensitive measurements, as well as for selective and controlled interventions, by employing unique diagnostic, analytical and conservation tools and methodologies. A number of demanding Cultural Heritage research questions and application challenges can be thus effectively responded to. Within the last twenty years, significant advances in laser light technology allowed the differentiation and imaging of different layers and strata within a painting at a sub-micrometre level, the detection of invisible defects within its bulk and the determination of risk prioritisation maps, the visualisation of the paintings’ response to abrupt environmental changes, the identification of materials at the atomic and molecular level and, last but not least, the controlled and selective removal of unwanted material and/or over-layers. This chapter aims to highlight the role of lasers as analytical, diagnostic and cleaning tools for painted artworks. Optical metrology, multi-photon excitation fluorescence and higher harmonics generation imaging, spectroscopic analysis and material ablation will be discussed on the basis of their implementation in paintings conservation, through brief scientific introduction and case study descriptions. Furthermore, advantages and limitations will be underlined with an emphasis on future challenges and prospects.