Optical and spectroscopic tools for evaluating Er:YAG laser removal of shellac varnish

Year: 2015

Authors: Striova J., Salvadori B., Fontana R., Sansonetti A., Barucci M., Pampaloni E., Marconi E., Pezzati L., Colombini M.P.

Autors Affiliation: National Institute of Optics/CNR, florence, Italy;
Institute for Conservation and Valorization of Cultural Heritage/CNR, Sesto Fiorentino (FI) and Milan, Italy;
University of Florence, Florence, Italy

Abstract: We report on tests to remove naturally and artificially aged shellac varnish by laser and traditional chemical cleaning from the substrates of mural paintings. Optical tools were used for the evaluation of cleaning processes, in particular laser microprofilometry to assess the changes in the surface morphology and time-domain confocal optical coherence tomography (OCT) to evaluate varnish thickness. The cleaning assessment was integrated with molecular characterization provided by portable Fourier transform infrared spectroscopy operating in reflectance mode, and colorimetric measurements. This complete analytical approach led to optimized laser-based cleaning tests at 1.9 and 2.6 J/cm(2) in the presence of isopropanol, which ensured controllable and safe partial removal of shellac varnish without alteration to the substrate morphology.


Volume: 60      Pages from: S91  to: S96

KeyWords: Cleaning; Erbium; Fourier series; Fourier transform infrared spectroscopy; Optical tomography; Substrates; Tomography; Varnish, Analytical approach; Colorimetric measurement; Er: YAG; FTIR; Molecular characterization; Mural paintings; Shellac; Substrate morphologies, Chemical cleaning
DOI: 10.1179/0039363015Z.000000000213

Citations: 20
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