Published September 22, 2018 | Version v1
Preprint Open

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

  • 1. CNR-INO National Institute of Optics, National Research Council
  • 2. Instituto de Química Física Rocasolano, CSIC
  • 3. Instituto de Estructura de la Materia, CSIC

Description

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.

Notes

The research leading to these results was funded by the EU Community's H2020 Research Infrastructure program under the IPERION CH Project (GA 654028) and by Ministerio de Economía, Industria y Competitividad (MINECO) of Spain under Project CTQ2016-75880-P.

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Additional details

Funding

European Commission
IPERION CH – Integrated Platform for the European Research Infrastructure ON Cultural Heritage 654028