In-Depth Analysis of Egg-Tempera Paint Layers by Multiphoton Excitation Fluorescence Microscopy

Year: 2020

Authors: Dal Fovo A., Sanz M., Oujja M., Fontana R., Mattana S., Cicchi R., Targowski P., Sylwestrzak M, Romani A., Grazia C, Filippidis G., Psilodimitrakopoulos S., Lemonis A., Castillejo M.

Autors Affiliation: CNR, Ist Nazl Ott, CNR INO, Largo Enrico Fermi 6, I-50125 Florence, Italy; CSIC, Inst Quim Fis Rocasolano, Serrano 119, Madrid 28006, Spain; Nicolaus Copernicus Univ Torun, Fac Phys Astron & Informat, Inst Phys, Grudziadzka 5, PL-87100 Torun, Poland; Ctr Eccellenza SMAArt, Dipartimento Chim Biol & Biotecnol, Via Elce Sotto 8, I-06123 Perugia, Italy; Fdn Res & Technol FORTH, Inst Elect Struct & Laser IESL, N Plastira 100, Iraklion 71110, Crete, Greece.

Abstract: The non-invasive depth-resolved imaging of pictorial layers in paintings by means of linear optical techniques represents a challenge in the field of Cultural Heritage (CH). The presence of opaque and/or highly-scattering materials may obstruct the penetration of the radiation probe, thus impeding the visualization of the stratigraphy of paintings. Nonlinear Optical Microscopy (NLOM), which makes use of tightly-focused femtosecond pulsed lasers as illumination sources, is an emerging technique for the analysis of painted objects enabling micrometric three-dimensional (3D) resolution with good penetration capability in semi-transparent materials. In this work, we evaluated the potential of NLOM, specifically in the modality of Multi-Photon Excitation Fluorescence (MPEF), to probe the stratigraphy of egg-tempera mock-up paintings. A multianalytical non-invasive approach, involving ultraviolet-visible-near infrared (UV-Vis-NIR) Fiber Optics Reflectance Spectroscopy, Vis-NIR photoluminescence, and Laser Induced Fluorescence, yielded key-information for the characterization of the constituting materials and for the interpretation of the nonlinear results. Furthermore, the use of three nonlinear optical systems allowed evaluation of the response of the analyzed paints to different excitation wavelengths and photon doses, which proved useful for the definition of the most suitable measurement conditions. The micrometric thickness of the paint layers, which was not measurable by means of Optical Coherence Tomography (OCT), was instead assessed by MPEF, thus demonstrating the effectiveness of this nonlinear modality in probing highly-scattering media, while ensuring the minimal photochemical disturbance to the examined materials.

Journal/Review: SUSTAINABILITY

Volume: 12 (9)      Pages from: 3831-1  to: 3831-15

More Information: This research was funded by the European H2020 IPERION CH Project (Integrated Platform for the European Research Infrastructure ON Cultural Heritage (GA 654028, WP6); Spanish State Research Agency (AEI) and European Regional Development (FEDER) through Project CTQ2016-75880-P-AEI/FEDER, UE; and TOP Heritage-CM (S2018/NMT-4372) from the Community of Madrid and with the support of Plataforma Tematica Interdisciplinar of CSIC Patrimonio Abierto: Investigacion y Sociedad (PTI-PAIS).
KeyWords: nonlinear optical microscopy; multi-photon excitation fluorescence; optical coherence tomography; egg-tempera paintings; non-invasive stratigraphy
DOI: 10.3390/su12093831

Citations: 9
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