Scientific Results

Multianalytical non-invasive characterization of phthalocyanine acrylic paints through spectroscopic and non-linear optical techniques

Year: 2019

Authors: Dal Fovo A., Oujja M., Sanz M., Martinez-Hernandez A., Canamares MV., Castillejo M., Fontana R.

Autors Affiliation: CNR INO, Largo Enrico Fermi 6, I-50125 Florence, Italy; Univ Firenze, Dip Chim, Via Lastruccia 3, I-50019 Florence, Italy; CSIC, Inst Quim Fis Rocasolano, Serrano 119, Madrid 28006, Spain; CSIC, Inst Estruct Mat, Serrano 121, Madrid 28006, Spain

Abstract: The documentation and monitoring of cleaning operations on paintings benefit from the identification and determination of thickness of the materials to be selectively removed. Since in artworks diagnosis the preservation of the object’s integrity is a priority, the application of non-invasive techniques is commonly preferred. In this work, we present the results obtained with a set of non-invasive optical techniques for the chemical and physical characterization of six copper-phthalocyanine (Cu-Pc) acrylic paints. Cu-Pc pigments have been extensively used by artists over the past century, thanks to their properties and low cost of manufacture. They can also be found in historical paintings in the form of overpaints/retouchings, providing evidence of recent conservation treatments. The optical behaviour and the chemical composition of Cu-Pc paints were investigated through a multi-analytical approach involving micro-Raman spectroscopy, Fibre Optics Reflectance Spectroscopy (FORS) and Laser Induced Fluorescence (LIF), enabling the differentiation among pigments and highlighting discrepancies with the composition declared by the manufacturer. The applicability of Non Linear Optical Microscopy (NLOM) for the evaluation of paint layer thickness was assessed using the modality of Multi-photon Excitation Fluorescence (MPEF). Thickness values measured with MPEF were compared with those retrieved through Optical Coherence Tomography (OCT), showing significant consistency and paving the way for further non-linear stratigraphic investigations on painting materials. (C) 2018 Published by Elsevier B.V.

Journal/Review: SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY

Volume: 208      Pages from: 262  to: 270

KeyWords: Spectroscopic techniques; Non-invasive analysis; Phthalocyanine paints; Non-linear optical microscopy; Multi-photon excitation fluorescence; Optical coherence tomography; Stratigraphy
DOI: 10.1016/j.saa.2018.09.040

Citations: 2
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