Multianalytical Study of Laser Pulse Duration Effects in the IR Laser Cleaning of Wall Paintings from the Monumental Cemetery of Pisa

A Andreotti,A Nevin,P Pouli,K Melessanaki,M P Colombini,C Fotakis

doi:10.1155/2006/39046

Abstract

The feasibility of laser cleaning for the removal of a variety of surface deposits from fragments of real wall paintings from the monumental cemetery of Pisa using Nd:YAG at 1064 nm at (μs), (ns), and (ps) regimes is presented. Multianalytical investigations of the samples from irradiated surfaces of fragments were carried out in order to characterize the original and added materials and to detect any laser-induced alterations; analysis included scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), laser-induced breakdown spectroscopy (LIBS), pyrolysis-gas chromatography-mass spectrometry (PY-GC-MS), and gas chromatography-mass spectrometry (GC-MS). The presence of nitrocellulose and pure lead contaminations on the surface of the samples has been identified. Assessment of the laser cleaning has highlighted the importance of the optimization of laser parameters, specifically pulse duration and fluence at the specified wavelength.

Highlights

The use of lasers to selectively remove unwanted materials from sensitive surfaces is well studied and has extensive applications [1], including the conservation of cultural heritage
The aim of this work is to assess the feasibility of the use of laser cleaning for the removal of surface deposits from fragments of real wall paintings from the monumental cemetery of Pisa using Nd:YAG laser irradiation at 1064 nm with pulse durations of μs, ns, and ps
The diagnosis of the constituents of works of art is of primary importance before starting the laser cleaning; the fragments of the wall painting were covered with surface deposits and encrustations of unknown origin, and it was necessary to identify the contaminant materials

Summary

Introduction

The use of lasers to selectively remove unwanted materials from sensitive surfaces is well studied and has extensive applications [1], including the conservation of cultural heritage. Lasers have been used as a highly controllable cleaning tool for the removal of dirt and various layers; numerous successful case studies on the laser cleaning of a variety of materials have been reported and include stone, varnished icons and paintings, metals, and paper [2, 3]. Laser-induced pigment alterations have been indicated as problematic in various studies of the cleaning of wall paintings [4, 5] and this has led to a series of model investigations of the physiochemical parameters that may induce and influence alterations [6,7,8]. Investigations of the photothermal reactions on polymer-based materials have been studied in a variety of model systems [9, 10] and on varnishes [11]

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Conclusion