Pollution Encrustation Removal by Means of Combined Ultraviolet and Infrared Laser Radiation: The Application of this Innovative Methodology on the Surface of the Parthenon West Frieze

Pouli, Paraskevi; Frantzikinaki, K.; Papakonstantinou, E.; Zafiropulos, V.; Fotakis, C.

doi:10.1007/3-540-27176-7_41

Cited by 15 publications

(11 citation statements)

References 2 publications

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“…In order to approach this delicate issue, namely the discoloration of the treated surface of polluted marble following irradiation with IR laser beams, research efforts have been focused on the identification of the composition of the environmental encrustation [13,17] in relation to the series of cleaning tests at different laser parameters [5,9,18]. Physicochemical analyses and evaluation of the treated surfaces and/or the material removed [7,12,15,19] were also employed to further investigate the yellowing issue.…”

Section: The Yellowing Effectmentioning

confidence: 99%

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Towards the understanding of the two wavelength laser cleaning in avoiding yellowing on stonework: a micro-Raman and LIBS study

Παπανικολάου¹,

Siozos²,

Philippidis³

et al. 2017

Proceedings of the International Conference LACONA XI

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The synchronous use of Infrared (IR at 1064nm) and Ultraviolet (UV at 355nm) wavelengths of a Q-Switched Nd:YAG laser has been shown to efficiently confront the issue of discoloration, which may be observed upon laser ablation of environmental encrustation from marble surfaces, and thus this methodology is effectively employed in various laser cleaning applications. In order to further investigate the mechanisms that influence this result, a series of tests were undertaken on fragments of marble with environmental homogeneous compact crust. Through a number of irradiation tests applying a variety of laser parameters (individual use of IR and UV beams, as well as, their synchronous use) the different ablative processes have been investigated. In this paper, micro-Raman and Laser Induced Breakdown Spectroscopy (LIBS) were employed in order to examine the role of each laser beam, as well as their combination, and so to approach the reasons that induce yellow discoloration. The results of the above studies will be presented with the aim to further describe the two wavelength laser cleaning methodology and its principle, thus elucidating its effectiveness.

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Section: The Yellowing Effectmentioning

confidence: 99%

“…Thus it is possible to select a final output ratio F IR / F UV = 1/4 or 4/1 and therefore get a different cleaning result. It should be noted that the decision on the ratios presented in this paper is the result of extensive past studies [5].…”

Section: Experimental Parametersmentioning

confidence: 99%

Towards the understanding of the two wavelength laser cleaning in avoiding yellowing on stonework: a micro-Raman and LIBS study

Παπανικολάου¹,

Siozos²,

Philippidis³

et al. 2017

Proceedings of the International Conference LACONA XI

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“…This piece of new marble of the same origin to the ancient marble pieces (Pentelic quarry) shows the same encrustation to the rest of the Parthenon Frieze and thus could be used for the purpose of this study. Previous studies [32,33] have determined the ablation threshold values for the thin pollution crust in the IR and UV regime to be respectively F IR_crust = 0.8 J/cm 2 and F UV_crust = 0.6 J/cm 2 the crust appears rather discoloured into grey, while at F slightly higher (F UV_4 = 0.4 J/cm 2 ) damage of the marble substrate is visible as broken shiny marble crystals are revealed.…”

Section: The Two-wavelength Cleaning Methodology; Background Informatmentioning

confidence: 96%

The two-wavelength laser cleaning methodology; theoretical background and examples from its application on CH objects and monuments with emphasis to the Athens Acropolis sculptures

et al. 2016

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The two-wavelength laser cleaning methodology has been introduced and developed in order to meet demanding cleaning challenges in CH. The innovation lies on the combined use of two laser beams, allowing thus control of the laser ablation effective regimes towards an efficient and safe cleaning result. A series of studies on technical samples and real fragments aimed at defining and refining this methodology in order to ensure that the original surface, including its details and historic traces, will be safeguarded. In this paper related research and applications will be presented in an attempt to enlighten the associated laser ablation processes, as well as the potential cleaning applications in CH field. Laser-assisted removal of pollution accumulations from the Athens Acropolis monuments and sculptures is a unique highlight on the use of this methodology in practice. IESL-FORTH in collaboration with the Acropolis Restoration Service and the Acropolis Museum has developed an innovative cleaning methodology and a prototype laser cleaning system, which since 2002 have been introduced to the everyday conservation practice and will be presented in this paper.

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“…Previous studies have proved the efficiency of this ablative regime to remove thick and hard encrustations (Cooper, 1998;Fotakis et al, 2006). There is always concern that IR laser cleaning may cause unwanted colour alteration to yellower hues (Pouli et al, 2005;Frantzikinaki et al, 2007;Pouli et al, 2008). In parallel, the ultraviolet (UV) cleaning regime was also tested using the third harmonic beam generated from a Q-switched Nd:YAG laser, at 355 nm.…”

Section: Irradiation Conditions and Methodologymentioning

confidence: 99%

“…The system, which emits short pulses of 6 ns pulse duration in the fundamental (1064 nm) and its third harmonic (355 nm) frequencies, has the ability to emit the two beams either independently or in combination, in spatial and temporal overlapping and in various ratios of fluences F IR /F UV (Pouli et al, 2005(Pouli et al, , 2008Frantzikinaki et al, 2007). Beam delivery was achieved through a system of highly reflecting mirrors, while the beam was tightly focused using a lens with focal length 25 cm.…”

Section: Irradiation Conditions and Methodologymentioning

confidence: 99%

Laser-assisted removal of dark cement crusts from mineral gypsum (selenite) architectural elements of peripheral monuments at Knossos

Grammatikakis¹,

Demadis

Melessanaki

et al. 2015

Studies in Conservation

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The aim of this study was the efficient removal of dark cement crusts from selenite (mineral gypsum) surfaces using lasers. The conservation challenge is to remove a hard, insoluble, and often significantly thick encrustation without affecting the particularly sensitive mineral substrate gypsum, which is susceptible to chemical transformation. Preliminary studies were focused on the determination of removal thresholds for the cement bulk and the establishment of efficient laser cleaning operative parameters. Concurrently, analytical investigations were focused on the irradiated surfaces in order to ensure that the recommended laser operating parameters would safeguard the surface, colour, and composition of gypsum. Analytical techniques (Raman spectroscopy, X-ray powder diffraction, scanning electron microscopy with energydispersive X-ray analysis) were used to verify that no discolouration or chemical alteration occurred to the fragile gypsum substrate due to the dehydration of pristine gypsum (to hemihydrate and anhydrous calcium sulphate). The results of this study as well as its application are presented and discussed with emphasis on the surface integrity of the exposed fragile selenite substrates.

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Pollution Encrustation Removal by Means of Combined Ultraviolet and Infrared Laser Radiation: The Application of this Innovative Methodology on the Surface of the Parthenon West Frieze

Cited by 15 publications

References 2 publications

Towards the understanding of the two wavelength laser cleaning in avoiding yellowing on stonework: a micro-Raman and LIBS study

Towards the understanding of the two wavelength laser cleaning in avoiding yellowing on stonework: a micro-Raman and LIBS study

The two-wavelength laser cleaning methodology; theoretical background and examples from its application on CH objects and monuments with emphasis to the Athens Acropolis sculptures

Laser-assisted removal of dark cement crusts from mineral gypsum (selenite) architectural elements of peripheral monuments at Knossos

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