Laser removal of water repellent treatments on limestone

Abstract Protective and water repellent treatments are applied on stone materials used on buildings or sculptures of artistic value to reduce water intrusion without limiting the natural permeability to water vapour of the material. The effect of the wavelength associated with the laser removal of two water repellent treatments applied on limestone, Paraloid B-72, a copolymer of methyl acrylate and ethyl methacrylate, and Tegosivin HL-100, a modified polysiloxane resin, was investigated by using the four harmonics of a Q-switched Nd:YAG laser (1064, 532, 355 and 266 nm). The modifications induced on the surface of limestone samples by laser irradiation were studied using colorimetry, roughness measurements and scanning electron microscopy (SEM). The removal of the treatments was found to be dependent on the laser irradiation conditions and on the characteristics of the coatings. The fundamental laser radiation was effective in removing both treatments, but thermal alteration processes were induced on the constituent calcite crystals. The best results were obtained by irradiation in the near UV at 355 nm.

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

[2]  Eric Doehne,et al.  Stone Conservation: An Overview of Current Research , 1998 .

[3]  A. E. Charola,et al.  ON THE REVERSIBILITY OF TREATMENTS WITH ACRYLIC/SILICONE RESIN MIXTURES , 1986 .

[4]  R. Heeren,et al.  Analytical study of the chemical and physical changes induced by KrF laser cleaning of tempera paints. , 2002, Analytical chemistry.

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

[6]  Thomas Lippert,et al.  Chemical and spectroscopic aspects of polymer ablation: special features and novel directions. , 2003, Chemical reviews.

[7]  Vassilis Zafiropulos,et al.  Discoloration of marble during laser cleaning by Nd:YAG laser wavelengths , 2001 .

[8]  Barbara Appelbaum,et al.  Criteria for treatment: reversibility , 1987 .

[9]  C. Fotakis,et al.  On-Line Monitoring of Laser Cleaning of Limestone by Laser-Induced Breakdown Spectroscopy and Laser-Induced Fluorescence , 1997 .

[10]  Roberto Sastre,et al.  Cleaning graffitis on urban buildings by use of second and third harmonic wavelength of a Nd:YAG laser: a comparative study , 2003 .

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

[12]  Rafael Fort,et al.  Chromatic parameters as performance indicators for stone cleaning techniques , 2000 .

[13]  S. Georgiou,et al.  Laser-induced material ejection from model molecular solids and liquids: mechanisms, implications, and applications. , 2003, Chemical reviews.

[14]  D. Krajnovich,et al.  Incubation and Photoablation of Poly(methyl methacrylate) at 248 nm. New Insight into the Reaction Mechanism Using Photofragment Translational Spectroscopy , 1997 .

[15]  Koenraad Van Balen,et al.  Technological Requirements for Solutions in the Conservation and Protection of Historic Monuments and Archaeological Remains' Final Report for the European Parliament Scientific and Technological Options Assessment Unit (STOA Project 2000/13-CULT/04 , 2001 .

[16]  D. C. Emmony,et al.  Characterization of laser cleaning of limestone , 1995 .

[17]  Paraskevi Pouli,et al.  Yellowing effect and discoloration of pigments: experimental and theoretical studies , 2003 .

[18]  Martin Cooper,et al.  Laser cleaning in conservation : an introduction , 1998 .

[19]  R. F. González,et al.  Basic methodology for the assessment and selection of water-repellent treatments applied on carbonatic materials , 2001 .

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