Study of historical glass grisailles by nonlinear optical microscopy

Abstract

Study of Historical Glass Grisailles by Non-linear Optical Microscopy M. Oujja(a), F. Agua(b), M. Sanz(a,c), D. Morales-Martin(b), M. Garcia-Heras(b), M.A. Villegas(b), M. Castillejo(a) (a) Instituto de Quimica Fisica Rocasolano (CSIC), C/ Serrano 119, 28006 Madrid, Spain (b) Instituto de Historia (CSIC), C/ Albasanz 26-28, 28037 Madrid, Spain (c) Departamento de Fisica Interdisciplinar, Facultad de Ciencias, Universidad Nacional de Educacion a Distancia (UNED), Senda del Rey 9, 28040 Madrid, Spain. In this work, the characterization via the Nonlinear Optical Microscopy (NLOM) modality of Multi-Photon Excitation Fluorescence (MPEF) of grisaille paint layers on historical stained glasses from different chronology and provenance in Spain is presented. Complementary glass analysis of the pieces was carried out by applying Laser Induced Breakdown Spectroscopy (LIBS) and Laser Induced Fluorescence (LIF) techniques. The grisaille paint layers studied display sufficient degree of transparency at the wavelength of 800 nm of the excitation femtosecond laser and in the spectral range of the emitted multiphoton fluorescence, making possible the non-invasive determination of the thicknesses of the grisaille paint layers by MPEF in the reflection configuration. The thickness values obtained by MPEF, in the range of 25 to 80 microns, were compared with those retrieved through Field Emission Scanning Electron Microscopy-Energy Dispersive X-ray Spectrometry (FESEM-EDS) measurements, showing good consistency and agreement. These results serve to validate the MPEF modality of NLOM for the non-destructive study of grisaille layers on historical glass substrates. Acknowledgments: This research has been funded by the Spanish State Research Agency (AEI) through projects PID2019-104124RB-I00/AEI/10.13039/501100011033 and PID2019-104220RB-I00 / AEI /10.13039/501100011033, by project TOP Heritage-CM (S2018/NMT-4372) from Community of Madrid, by EU H2020 project IPERION HS (GA 871034) and supported by CSIC Interdisciplinary Platform “Open Heritage: Research and Society” (PTI-PAIS). The authors acknowledge professional support from the TechnoHeritage Network of Science and Technology for the Conservation of Cultural Heritage.