Monitoring the restoration of a seventeenth-century wooden artwork using means of laser-induced fluorescence and digital image analysis

Abstract

The present paper is aimed at demonstrating the capabilities of digital image analysis (DIA) to support conservation of painted artwork. Laser-induced fluorescence (LIF) imaging has been usually used in the diagnosis of wall paintings. In this case, LIF is applied to the case study of a painted wooden canopy, and most successful data processing techniques are presented in the discussion of results. The Jesús del Gran Poder canopy, completed by Francisco Ruiz Gijón in 1692, is an oil panel painting on wood. Eight panels of the canopy have been study by LIF. This technique is capable of remotely acquiring hyperspectral images operating in fluorescence mode following ultraviolet laser excitation. LIF spectra combined with principal component analysis, spectral angle mapper, and DIA provide a chemical mapping of the treated wooden surface of the panels. Besides, LIF spectrum is as a fingerprint of the panels that allows stablishing differences between them. LIF imaging analysis has proven to be a very useful tool for mapping retouching work, tracking previous restorations, and detecting chemicals on the wood in order to monitor restorations.