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13th International Conference on Lasers in the Conservation of Artworks, Florence ­ September 12­-16, 2022, The financial support of this work has been provided by the H2020 European project IPERION HS (Integrated Platform for the European Research Infrastructure ON Heritage Science, GA 871034), by the project CNR4C­PLAS@rt” co­financed by the Tuscany Region and El.En. S.p.A., and by the Spanish State Research Agency (AEI) through project PID2019­104124RB­I00/AEI/ 1013039/501100011033. Support from CSIC Interdisciplinary Platform “Open Heritage: Research and Society” (PTI­PAIS) is acknowledged.

XIII LACONA “Lasers in the Conservation of Artworks", Florence, on September 12-16, 2022 . -- http://www.lacona13.eu/#, Varnishes are employed in painted artworks for protection from atmospheric pollution and oxidation and for improving the aesthetic appearance of paintings by providing an even and brilliant surface finish. Varnishes undergo complex and differentiated structural and chemical changes over time depending on their composition and conservation conditions. The present work investigates the degradation due to aging of the outermost layers of varnishes as a function of depth by using nonlinear optical microscopy (NLOM) [1] in the modality of multiphoton excitation fluorescence (MPEF). This totally noninvasive technique has been employed for the determination, with a high axial and lateral resolution, of the affected regions of pictorial varnish layers resulting from various types of degradation [2,3]. In this work, terpenoid varnishes such as dammar, mastic, shellac and sandarac, subjected to various types and degrees of aging, natural, artificial and a combination of the two, were tested. A homemade nonlinear optical microscope, based on a tightly focused pulsed femtosecond laser emitting at 800 nm, was used for the investigation. Singlephoton laserinduced fluorescence (LIF) measurements served to determine the degree of surface aging and the optimum NLOM-MPEF operating conditions and helped to interpret the results obtained applying the latter [4]. These results signpost the correlations of the nature of the varnish layer, the initial thickness and the type and extent of aging with the indepth degradation gradients determined by NLOM-MPEF. ACKNOWLEDGMENTS This research has been funded by the Spanish State Research Agency (AEI) through project PID2019104124RBI00/ AEI/ 1013039/501100011033, by the H2020 European project IPERION HS (Integrated Platform for the European Research Infrastructure ON Heritage Science, GA 871034). Support by CSIC Interdisciplinary Platform ¿Open Heritage: Research and Society¿ (PTIPAIS) is acknowledged. REFERENCES [1] A. Dal Fovo, M. Castillejo, R. Fontana, Nonlinear optical microscopy for artworks physics, La Rivista del Nuovo Cimento 44 (2021) 453498. [2] G. Filippidis, M. Mari, L. Kelegkouri, A. Philippidis, A. Selimis, K. Melessanaki, M. Sygletou, C. Fotakis, Microsc. Microanal. 21 (2015) 510517. [3] M. Oujja, S. Psilodimitrakopoulos, E. Carrasco, M. Sanz, A. Philippidis, A. Selimis, P. Pouli, G. Filippidis, M. Castillejo, Phys. Chem. Chem. Phys. 19 (2017) 2283622843. [4] D. Ciofini, M. Oujja, M. V. Cañamares, S. Siano, M. Castillejo, Microchem. J., 141 (2018) 1224., This research has been funded by the Spanish State Research Agency (AEI) through project PID2019­104124RB­I00/AEI/ 1013039/501100011033, by the H2020 European project IPERION HS (Integrated Platform for the European Research Infrastructure ON Heritage Science, GA 871034). Support by CSIC Interdisciplinary Platform “Open Heritage: Research and Society” (PTI­PAIS) is acknowledged.

In the project "ARCHEO 3.0" a Machine Learning (ML) system for automatic contouring of the stratigraphic units of an archaeological excavation has been experimented. In this research, we have applied the same ML algorithm to aerial color photographs that represent very important tools in the study of ancient topography and landscape archaeology. Aerials of the Vulci necropolis, one of the most important cities of ancient Etruria, have been used. These photos, both vertical and oblique, have been chosen because the marks had been studied and analyzed in a recent PhD work in Ancient Topography. In particular, the traditional mapping method has been compared with the results obtained by means of automated ML algorithm. This experiment has demonstrated that the developed ML algorithm can be applied to aerial photographs for the recognition of archaeological traces, with interesting development prospects.

The authors regret finding a mistake in colour labels of Fig. 3b. Please find attached the figure corrected. [Figure presented] The authors would like to apologise for any inconvenience caused.

This work presents the results of a National Italian Project (PRIN, period 2011-2014) aiming at the development of new methodologies for the conservation of bronze and gilded bronze artefacts. Fire-gilded bronze is a precious material, widely used for historical artworks as well as in architectural elements and often exposed to aggressive atmospheres. There, it suffers extensive corrosion damage, due to galvanic coupling between the underlying bronze and the thin, highly defective gilded layer. Protective surface treatments, monitoring methods by electrochemical sensors and controlled-microclimate open showcases can represent quite useful measures against bronze and gilded bronze degradation.

Fluence (J/cm2) and reflectance are key parameters in pulsed laser ablation processes. The dynamics and rate of the material removal are strictly dependent on the energy dissipated into the material under irradiation, which is complementary to the reflected energy. Laser cleaning of artifacts of cultural interest is a well-known application of laser ablation, which significantly grew along the last decade. The Long Q-Switch Nd:YAG laser (1,064 nm, ?=120 ns) is one of the most used laser systems (Salimbeni et al., J Cult Herit 4(1):72-76, 2003; Cacciari et al. Chem 402(4):1585-1591, 2012; Siano et al., Appl Phys A 106(2):419-446, 2012). This is usually equipped with optical fiber beam delivery terminated with a handpiece including an imaging lens and a mechanical arrangement to vary the fiber-to-lens distance in order to suitably set the laser spot diameter at the target. In this way, skilled restorers can set the operating fluence according to the interaction phenomenology observed. Here, a novel laser handpiece equipped with optical sensors in order to monitor fluence at the target and its reflectance, as well as the optimum working distance, is presented.

Pulsed neutron beams available at the ISIS spallation source offer diverse possibilities for materials characterization using diffraction and imaging. In this paper we review a range of applications of the time-of-flight neutron diffraction for the characterization of phase transformation and residual stress states in industrially-relevant situations. The setup of the ENGIN-X instrument at ISIS is described, followed by a series of case studies based on the recently obtained results.

The laser cleaning problem of gold leaf gilded surfaces was investigated here. Preliminary irradiation tests carried out on pure gold leaf standards evidenced the crucial importance of the laser pulse duration for avoiding serious damages. Optimised pulse duration providing good cleaning results with negligible side eects was then selected and successfully used in the restoration of three Renaissance masterpieces.

The INES project was sponsored by the CNR Neutron Spectroscopy Advisory Committee, stressing the importance of realizing an Italian Neutron Experimental Station (INES) at the world most powerful pulsed neutron source (ISIS, Rutherford Appleton Laboratory, UK) and evidencing the strategic value that such a test station would assume in the field of applied sciences like, for example, chemistry, material science, Earth science, crystallography, and last, but not least, in the field of science applied to the study of cultural heritage artifacts.

The present work focuses on the main phenomenological features of stone cleaning by lasers. They are the removal rate, degree of cleaning, and chromatic appearance of the treated surface associated with different conservation problems and laser parameters. A set of three different outdoor stone conservation problems were investigated here. The measurement of the ablation rates were carried out on encrusted stone artefacts and two sets of prepared samples in order to derive general behaviour through repeatable measurements. The analysis of the irradiation tests provided a quantification of the different efficiencies, degree of cleaning, and chromatic appearances associated with the fundamental harmonic of Q-switching, long Q-switching, and short free running Nd:YAG lasers (1,064 nm), as well as with the second harmonic of Q-switching sources (532 nm).

Studio di bronzi archeologici con diffrazione di neutroni

We report what to our knowledge is the first application of laser welding in conservation of artworks. This technique is presently carried out at the Goldsmith Laboratory of the Opificio delle Pietre Dure in Florence to restore a precious ostensory of the 17th century made of gold, silver, painted enamels and gems. Before the restoration, the object was lying broken in more than 300 fragments of various sizes. The reconstruction of the ostensory has been carried out by using a long Nd:YAG laser equipped with stereomicroscope for precise control of the operations, which allowed welding spots of a few hundreds of microns.

In previous laser cleaning tests and analyses carried out on fossil bones, we demonstrated the feasibility and effectiveness of the laser approach. Based on these results, we designed cleaning procedure employing fibre-optic-delivered Nd:YAG laser radiation, integrated with other conventional cleaning techniques, such as micro-sandblasting and chemical cleaning. The procedure has been optimised for application on important specimens, such as the fossil human "skull of Buia", recently discovered by a research expedition of the Department of Earth Sciences of the University of Florence and presently preserved in the Museum of Asmara (Eritre). Here, we report laser cleaning tests where this procedure has been applied on samples of other mammalian bones from Danakil depression and the site of matassino (Italy)

An optimised laser methodology was devised to clean gilded decorations found on hair and robes of the Santi Quattro Coronati, marble sculptures by Nanni di Banco. The optimisation of laser parameters was achieved through comparative cleaning tests by employing Nd:YAG (1064nm) and Nd:YAP (1340 nm) lasers systems. The different cleaning results were characterised by microscopy, spectral reflectometry, and FT-IR analyses. In particular, high removal control was achieved by short free running (SFR) Nd:YAP and Nd:YAG lasers that allowed gradual cleaning levels. Conversely, a single cleaning level was possible by Q-switching Nd:YAG laser, which also induced an undesired yellowish-orange appearance of the cleaned surface. Following the analysis of these results the whole cleaning treatment of gilded areas was performed using SFR Nd:YAG laser.