Laser cleaning of marble: discoloration effects using various Nd:YAG laser wavelengths (ω, 2ω, 3ω)

This contribution focuses on the interaction of superficial deposits with the marble substrate during the removal by laser radiation. A comparison between cleaning results obtained by the first three harmonic wavelengths of a Q-switched Nd:YAG laser is shown. Experiments were carried out on two sample types. In order to simulate a black encrustation, a model sample was developed based on former studies. In the second case a naturally microbial encrusted marble sample was used. Additionally the temporal ablation development of CaCO3 was investigated by a high speed framing camera. The effects of Nd:YAG laser irradiation at 1064 nm, 532 nm and 355 nm were examined by laser induced breakdown spectroscopy (LIBS), scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDX) and color measurements using the Commission Internationale de l'Eclairge (CIE) Lab color system with respect to the development and the absolute surface color-change. The results show, that the surface color remaining after the removal of the artificial encrustation by the fundamental wavelength, turned from originally white to yellow. It was possible to identify an Iron content located in nanometer sized spheres on the surface to be the source of the yellowing. The third harmonic wavelength removed the encrustation without a discoloration, whereas the second harmonic was not able to remove the crust appropriately. To remove a superficial biogenic encrustation the 2nd and 3rd harmonic were observed to be the most efficient wavelengths, supporting a good result, which could not be achieved by applying the fundamental wavelength.

[1]  A. Tam,et al.  Efficient pulsed laser removal of 0.2 μm sized particles from a solid surface , 1991 .

[2]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

[3]  M. Bacci,et al.  Color Analysis of the Brancacci Chapel Frescoes: Part II , 1993 .

[4]  Costas Fotakis,et al.  Laser-induced breakdown spectroscopy as a diagnostic technique for the laser cleaning of marble , 1997 .

[5]  Roberto Pini,et al.  SMART CLEAN: a new laser system with improved emission characteristics and transmission through long optical fibres , 2000 .

[6]  Costas Fotakis,et al.  Excimer laser cleaning of encrustation on Pentelic marble: procedure and evaluation of the effects , 1999 .

[7]  F. Marcos,et al.  Laser cleaning in art restoration , 1996 .

[8]  R. Newton,et al.  Conservation of glass , 1992 .

[9]  Martin Cooper,et al.  The use of laser cleaning to preserve patina on marble sculpture , 1996 .

[10]  Giancarlo Lanterna,et al.  Laser cleaning: a study on greyish alteration induced on non-patinated marbles , 2000 .

[11]  Mauro Bacci,et al.  A Color Analysis of the Brancacci Chapel Frescoes , 1991 .

[12]  Th. Skoulikidis,et al.  Mechanism of Sulphation by Atmospheric SO2 of the Limestones and Marbles of the Ancient Monuments and Statues: II. Hypothesis concerning the rate determining step in the process of sulphation, and its experimental confirmation , 1981 .

[13]  V. Vergès-Belmin,et al.  Pseudomorphism of gypsum after calcite, a new textural feature accounting for the marble sulphation mechanism , 1994 .

[14]  J. Molera,et al.  Interaction of rock and atmosphere: patinas on Mediterranean monuments , 1998 .

[15]  Werner Zapka,et al.  Laser‐cleaning techniques for removal of surface particulates , 1992 .

[16]  Leon J. Radziemski,et al.  Lasers-Induced Plasmas and Applications , 1989 .

[17]  I. Watson,et al.  Laser Remediation of Sandstone Contaminated with Microbial Growth and Bryophyte , 1996 .

[18]  R Salimbeni,et al.  Cleaning processes of encrusted marbles by Nd:YAG lasers operating in free-running and Q-switching regimes. , 1997, Applied optics.

[19]  Vassilis Zafiropulos,et al.  Laser-induced breakdown spectroscopy for on-line control of laser cleaning of sandstone and stained glass , 1999 .

[20]  Edwin D. Mares,et al.  On S , 1994, Stud Logica.

[21]  Vassilis Zafiropulos,et al.  Comparative study of different wavelengths from IR to UV applied to clean sandstone , 2000 .

[22]  Demetrios Anglos,et al.  Excimer laser restoration of painted artworks: procedures, mechanisms and effects , 1998 .

[23]  J. F. Asmus.  More light for art conservation , 1986, IEEE Circuits and Devices Magazine.

[24]  John F. Asmus,et al.  Studies On The Interaction Of Laser Radiation With Art Artifacts , 1974, Optics & Photonics.

[25]  John F. Asmus,et al.  HOLOGRAPHY IN THE CONSERVATION OF STATUARY , 1973 .

[26]  Th. Skoulikidis,et al.  Mechanism of Sulphation by Atmospheric SO2 of the Limestones and Marbles of the Ancient Monuments and Statues: I. Observations in situ (Acropolis) and laboratory measurements , 1981 .

[27]  Roberto Pini,et al.  Application of a new laser cleaning procedure to the mausoleum of Theodoric , 2000 .

[28]  J. P. Boquillon,et al.  Modelling and diagnostic of pulsed laser cleaning of oxidized metallic surfaces , 1996 .