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LACONA VI Proceedings
Edited by Johann Nimmrichter; Wolfgang Kautek; Manfred Schreiner
Reviewed by Rui Bordalo Vienna, Austria, Sept. 21-25, 2005 Series: Springer Proceedings in Physics Vol. 116 Year: 2007 Pages: 647 pp., 419 figures ISBN: 978-3-540-72129-1 (Hardcover) Price: $260 / €210
Metal (part I) is an important material but it is still far from being one of the most studied. This section contains 5 articles about laser cleaning of corroded steel, gildings, coins and the follow up of the laser cleaning of Ghiberti's Porta del Paradiso in Florence (page 29).
Besides being the first material where laser cleaning was employed, stone (part II) is the most studied material. However, on the middle of so many case studies and articles focused on the use of laser, it is interesting to read a reflection about the demand of laser cleaning in Austria. Pummer (page 143), based on his 10 years and 40,000 man hours experience, reveals that this technology (Nd:YAG laser) “or equivalent” is currently too often used in official service agreements, mostly without awareness. The author compared 2 usual techniques – microblasting and Nd:YAG laser - and concluded that, apart the high difference of cost per hour between them, the methods can not be referred to as equivalent concerning the cleaning results. Despite the fact that part III is dedicated to inorganic materials, a very comprehensive category, in this section are included those materials which didn’t fit the previous sections. Perhaps the most uncommon material in this section is the eggshell. Cornish et. al. (page 169), used a scanning electron microscope (SEM) to assess Nd:YAG laser cleaning on eggshell. Preliminary results show that Nd:YAG has potential, as no visible difference was identified by SEM, but that other more sensitive analytical techniques should be employed in order to fully establish the usefulness of this technology. The second biggest section is the one dedicated to organic materials (part IV). Textiles, paper and resins use to belong to this section, as well as Nd:YAG and excimer laser. However, Er:YAG lasers start to be often used and other materials investigated, such as polyurethane foam (page 295). On this regard, Staal Dinesen and Westergaard investigated the usefulness of using laser cleaning instead of vacuum cleaning of polyurethane foam (PU-foam), a normal material used in Contemporary art. It was proven that laser cleaning is more effective than vacuum cleaning on dust removal despite damaging some PUvariants. However, laser cleaning on PU-F was found recommended on the given parameters. Part V (analytical techniques) is devoted to material characterisation. Many of the materials characterised, either for their study or identification, are pigments or stone-based materials followed by paper, ceramics and others. The analytical techniques are mostly recurrent, such as Raman spectroscopy, laser-induced breakdown spectroscopy (LIBS), laserinduced plasma spectroscopy (LIF) and laser-induced fluorescence (LIF). Without disregarding the importance of other materials in this section, I believe that the characterisation study of cinematographic film, by Oujja et. al. (page 421), stands out by its unusual subject. The study reflects the suitability of LIBS to characterise silver-gelatine photographic film, to identify different gelatine types and to obtain information on developers and hardeners used on the film. The scanning techniques section (part VI) proves itself to be a highly considered field as it is the biggest section of the book. Its 18 articles confirm the huge range of this type of application to Cultural Heritage: from examination of paintings (page 487) and its cleaning (page 473) to damage assessment (page 543) and diagnosis of historical monuments (page 583). A good example is given by Bajraszewski et. al. that used optical coherence tomography (OCT) to assess the environmental influence on canvas paintings. Under laboratorial controlled conditions, the sample was submitted to humidity changes. OCT analysis revealed a 170 μm translation of the whole painting surface and quantified the morphologic change of the sample crack system, confirming the suitability and sensibility of this technique. Part VII (Safety and Miscellaneous) is the last and the smallest part of the book, with only 3 articles. Despite that laser presents exceptional advantages on laser cleaning, health safety assessment is a current necessity. Ostrowski et. al. (page 624) verified, using a nanosecond laser (15 ns), that at the highest laser fluence 78% of the particle matter is in the nanoparticle size range (30-100 nm). Barcikowski et. al. (page 631), collaborating with the previous author within the same project, draws a similar conclusion. However he compares nanosecond (15 ns) with femtosecond (120 fs) lasers. Among other conclusions, it is stated that femtosecond lasers produce finer particles. Health recommendations are also suggested such as the use of a built-in fume extraction. Concluding, I will be expecting the next proceedings of the recently finished LACONA VII which was held last September in Madrid, Spain.
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