Catálogo de publicaciones - libros

We report the results of a successful experimentation of the laser cleaning technique on wall paintings using intermediate pulse duration Nd:YAG lasers at the fundamental wavelength (1,064 nm).

Laser-induced fluorescence of intrinsic fluorophores of organic media found in paintings (casein, animal glue and egg proteins) provides a means of characterising general classes of media depending on the amino acid composition and presence of degradation cross-linkages. Wavelength dependence of spectra is investigated for non-destructive and non-invasive analyses of thin films of protein-based binding media.

Nano-particles are released from the material during short-pulse and ultrashort-pulse laser ablation. It is well known that nano-particles can cause adverse health effects. Therefore, the aim of the presented study is to assess the risks caused by nano-particulate emission during nanosecond (ns) and femtosecond (fs) laser cleaning. The size distribution of particulate matter (PM) in the fumes which emerge during Nd:YAG and Ti:Sapphire laser ablation is characterized using an automatic 12-level low pressure cascade impactor. It is shown that the mean diameter and the dispersion of the PM strongly depend on the laser parameters (fluence, pulse energy) and material (gypsum, graphite and paper).

Traditional paper cleaning techniques are not always sufficient for cleaning artefacts. The pulsed laser cleaning can offer a valuable tool for solving problematic cases in paper conservation. Comparative studies of traditional and laser cleaning were performed on historic picture post cards. The results demonstrate the possibilities of partial laser cleaning using nanosecond laser pulses at a wavelength of 532 nm.

Laser divestment entered the field of art conservation through a nonlinear sequence of positive accidental events (serendipity) that involved the cinema industry, the invention of spread-spectrum and frequency-hopping communications, nuclear space propulsion, and oceanography. The unlikely chain of events began with the invention of a secure military communications system by a Viennese motion picture actress (1942). A first evaluation of the novel communications concept took place during a high-altitude nuclear test (TEAK) over the Pacific Ocean in 1958. The secure radio link proved to be a failure; however, analyses of the backscattered electromagnetic radiation contributed to the realization that nuclear-explosion plasmas need not be spherically symmetrical. Nobel Laureate Freeman Dyson exploited this nuclear option to guide in the design and prototype development of the ORION spaceship that was to rendezvous with the planet Saturn in 1970.

Electronic speckle pattern interferometry (ESPI) has been used to monitor microdeformations and surface microstructure changes produced by crystallization or hydration pressure of magnesium sulfate in a porous material. Samples of fritted glass were chosen as a standard porous substrate because of its mean grain size, its porosity distribution, and its negligible humidity expansion. The glass samples, soaked with salt solution, were exposed to changes in relative humidity of the surrounding air. The full-field ESPI measurements were combined with cryogenic SEM visualizations. Results from these investigations were partly not expected theoretically and give new insight in the underlying salt phase transition processes.

This paper summarises the conservation of the Porta del Paradiso , currently underway. It briefly illustrates the two cleaning methods employed and the reasons leading to continue the cleaning of the perimeter panels with laser ablation, describing the various working phases.

The importance of Raman micro-spectroscopy for the identification of pigments in works of art is well established. In recent times, portable Raman spectrometers have been introduced which allows users to perform field analysis directly where the artefacts are placed (churches, museums, archaeological sites, etc.). The present work reports results obtained by a remarkably compact instrument, in particular, on frescoes and illuminated parchments.

Measurements aimed at optical characteristics of the basic building material of the Renaissance dome of King Sigismund’s Chapel in Wawel Castle are described in the paper. Colorimetric measurements, LIBS investigations and Raman effect measurements were carried out. LIBS spectra of encrusted and clean (fresh fractured) grey-greenish Myslenicki sandstone are presented. Raman spectra and reflection coefficients as well as L , a , b coordinates for several samples are also shown.

There is an established need for a portable and affordable Q-switched laser system for use in studio conservation and small scale field use. The ideal system would be capable of producing a variety of wavelengths ranging from the ultraviolet to the infrared with sufficient energy per pulse to treat a wide range of materials including stone, marble, terracotta, wood, organic materials, bone, parchment, textiles, and metals. In this paper we report on such a system which is capable of delivering Q-switched output at 1,064nm in excess of 300mJ per pulse and at repetition rates of up to 25 Hz. Additional outputs are also reported at 266 nm, 355 nm, 532 nm, and 2 . 94 μm. Preliminary cleaning results on a small range of objects using the Q-switched 1,064nm output are presented.