Workshop on Sustainable solutions for restoration & conservation of cultural heritage

Resume : The imaging technique using the frequency band in terahertz (THz) region (0.1 to 10 THz) has become an emerging topic heritage science. The biggest advantage of THz imaging is the nondestructive depth profiling by using THz pulse-echo in time domain. The delay of each reflection pulse from internal interface corresponds to the distance from the surface, and thus the layer structure can be obtained at any position of the painting, without taking a sample. This method has been practically used to observe preparation layers of panel paintings and screens. In the case of canvas paintings, the preparation layer has been considered too thin to be analysed by THz pulse-echo imaging. We have observed an oil canvas painting from a private collection, which partially has thick multiple paint layers. The thick paint layers can be recognised at edges and the original canvas was mounted on a thicker new canvas, in previous treatment. We applied the THz pulse-echo imaging to observe layer structure of the entire painting. Nondestructive cross section images easily show the interface between the original and new canvas layers, and multiple painted parts are also confirmed. However, the preparation layer and the painted layer which is obviously one brush stroke on the preparation, could not be distinguished from the original canvas due to the lack of resolution in depth direction. We discuss the potential and limitations of THz pulse-echo imaging for canvas painting investigations.

Resume : Preservation of cultural heritage is one of the key parts of education for future generation. The development of new portable instrumentation allows people in charge of conservation to study and enhance the knowledge of this heritage. The need of in situ characterization is growing due to the feasibility of implementation of new technics. Portable terahertz time-domain imaging and spectroscopy has been evolving as an investigative tool in the field of cultural heritage for conservation applications [1-3]. In the field of cultural heritage, this technic was first used for imaging the hidden painting under lime wash layer. This technic allows getting good multilayer structural information. Portable Libs (Laser Induced Breakdown Spectroscopy) is well known as elemental technic. The first applications for cultural heritage were focused on pigment identification [4-7]. Moreover, the force of this kind of optical instrumentation is presented by its capability to provide in depth information. This work aims at coupling both technics in order to characterize as well as possible different kind of hidden surface without sampling focusing on the mural painting conservation issues. Mocks-up were prepared including different picture using several pigments. In addition, some area have been prepared with gold leaf and then recovered by lime wash layer. Thz imaging was applied in order to identify the different layers and the picture represented and libs to identify the nature of the material composing the sample. In addition the effect of cyclododecane to enhance the efficiency of the technics has been investigated and will be presented. [1] J. Bianca Jackson, John Bowen, Gillian Walker, Julien Labaune, Gerard Mourou, Michel Menu and Kaori Fukunaga, ?A Survey of Terahertz Applications in Cultural Heritage Conservation Science,? IEEE Transactions on Terahertz Science and Technology 1 (2011) 220-231 [2] J.B. Jackson, M. Mourou, J. F. Whitaker, I. Duling, S. Williamson, M. Menu and G. Mourou ?Terahertz Imaging for Non-destructive Evaluation of Mural Paintings,? Optics Communications 281 (2008) 527?532. [3] Gillian C. Walker, John W. Bowen, Julien Labaune, J-Bianca Jackson, Sillas Hadjiloucas, John Roberts, Gerard Mourou, and Michel Menu ?Terahertz deconvolution? Optics Express, 20 (2012), 27230-27241 [4] Bruder R., Detalle V., Coupry C. ?An example of the complementarity of laser-induced breakdown spectroscopy and Raman microscopy for wall painting pigments analysis?, Journal of Raman Spectroscopy, volume 38, issue 7, pp. 909 ? 915, (2007) [5] Bruder R, L'Hermite D, Semerok A, Salmon L, Detalle V. ? Near-crater discoloration of white lead in wall paintings during laser induced breakdown spectroscopy analysis?. Spectrochim. Acta Part B 62:1590-1596, (2007) [6] Duch?ne S, Detalle V, Bruder R, Sirven JB. ?Chemometrics and laser induced breakdown spectroscopy (LIBS) analyses for identification of wall paintings pigments?. Curr. Anal. Chem. 6:60-65, (2010) [7] Gregoire S, Boudinet M, Pelascini F, Surma F, Detalle V, Holl Y. ?LIBS (Laser Induced Breakdown Spectroscopy) for polymer identification? Analytical and bioanalytical Chemistry Volume 400, Number 10, 3331-3340 (2011)

Resume : Electromagnetic sensing technologies deserve huge attention in the frame of cultural heritage, since theyare able to provide information about constructive techniques, restoration works, preservation status and risk factors affecting the integrity of artworksin a non-invasive and safety way. Among the electromagnetic techniques currently at the state of art, we focus on subsurface radar as well as THz spectroscopy and imaging systemsand summarize the main advancements in terms of data processing and results achievedat the Institute forElectromagnetic Sensing of the Environment - National Research Council of Italy (IREA-CNR). Subsurface radar systems are widely considered in archaeology and cultural heritage monitoring due to their ability to attain high-resolution images of thehidden features of a surveyed spatial region in a non-invasive way, by exploiting the ability of the microwaves to penetrate inside opaque materials. However, despiteof the simple electromagnetic sensing mechanism, their use in operative conditions is not of immediate impact. This is mainly due to the fact that raw radar images suffer of “blurring” effects, which make their interpretation very difficult andprone to the operators’ expertise. Therefore, a continuous research effort is on-going so to addressthe development of advanced data processing strategies, with the final aim ofproviding easily interpretable images, possibly in real-time.In this frame, model based data processing approacheshave been developed at IREA-CNR. These approaches recast the imaging as a linear inversescattering problem and arecapable of providing robust and reliable diagnostics in terms of high-resolution 2D and 3D images, which allows us to infer thegeometrical features of hidden targets. These approaches have been extensivelytested in a large number of real test sites [1-3] and at the conferencecases of microwave tomography enhanced GPR surveys will be presented as well as their potentiality at tools to properly plan and timely address maintenance actionsof historical structures. THz spectroscopy and imaging systems are attracting huge attention as complementary techniques to classical analysis methodologies based on X-rays to mid infrared radiations. As microwaves, THz signals are, indeed, non-ionizing radiations capable of penetrating dielectric materials, which are opaque to both visible and infrared waves[4-6].In addition, several substances exhibit absorption spectra at THz frequencies with specific fingerprints, which depend on their molecular behaviour. Therefore, THz waves allows characterization of manmade objects, with the possibility of discriminating different materials while assuring negligible long term risks to the molecular stability of the exposed objects. As a further advantage, in the last years, flexible and compact commercial systems having source and detector probes coupled by means of optical fiber cables and that do not require complex optical alignments have been developed.An example of last generation THz systems is the Fiber-Coupled Terahertz Time Domain System (FICO) developed by Z-Omega and recently acquired by the Institute of Electromagnetic Sensing of the Environment (IREA).Such a system works in the range from 0.1THz to 3THz and is equipped by a 15 cm x 15 cm motorized platform to perform planar scans of the investigated samples. The experiments carried out at the IREA laboratory and the obtained results will be presented at the conference with the aim to discuss on the potentialities offered by THz technologies in the frame of artworks characterizations. Keywords:Cultural Heritage Monitoring, Imaging, Microwaves, THz waves [1] G. Leucci, R. Persico and F. Soldovieri. Detection of fractures from GPR data: the case history of theCathedral of Otranto. J. Geophys. Eng., vol.4, pp.452–461, Dec. 2007. [2] I. Catapano et al., “Microwave tomography enhanced GPR surveys in Centaur’s Domus, regio VI of Pompei, Italy”, J. Geophys. Eng, vol. 9, pp. 92-99, 2012. [3] I. Catapano et al. “Full three-dimensional imaging via ground penetrating radar: assessment in controlled conditions and on field for archaeological prospecting”, Applied Physics A 115 (4), pp.1415-1422, 2014. [4] K. Fukunaga, I. Hosako, “Innovative non-invasive analysis techniques for cultural heritage using terahertz technology”, C. R. Physique, vol. 11, pp.519–526, 2010. [5] M. Perenzoni and D. J. Paul, Physics and Applications of Terahertz Radiation, Springer Series in Optical Sciences 173, 2014

Resume : During the last century the increasing environmental pollution in synergistic action with the natural weathering agents, has caused a rapid worsening of the conditions of the monuments exposed in urban areas. The main forms of deterioration on the stone facades are related to the accumulation of pollutants and to soiling processes, with the development of black crusts and other decay forms. Photocatalysis is an oxidation process that can be used for the decomposition of various environmental pollutants in both gaseous and liquid phases in a simple and efficient way.Among the photocatalytic materials, titanium dioxide is the most widely studied andthe photoactive nanocrystalline titania obtained by sol-gel process is a promising de-soiling coating material. In this paper we report on the results of a study on a new self-cleaning coating for carbonaticstones based on TiO2 nanoparticles obtained by sol-gel in a basic environment. Different types of limestone amongthe most frequently used in historic buildings were used as substrates. The water based TiO2sol was easily applied by brushing directly on the stone. The compatibility of the coatings with the substrate was examined according to the UNI-Normal protocols by measuring the water absorption by capillarity and colorimetric parameters. The characterization of the powders obtained by drying the sol at room temperature was made by -Raman spectroscopy and XRD. The penetration depth and surface distribution of the sol were evaluated with SEM-EDS. Photocatalytic oxidation of methyl orange (MeO) and methylene blue (MB) under fluorescent lamp irradiation (= 366 nm) was used as indicator of the catalytic activity of nano-TiO2 sol and TiO2coatings. XRD and Raman measurements confirm the crystalline nature of titaniain anatase form with negligible brookite. The Raman peak positions and FWHM suggest anatase nanocrystals with 5-10 nm size. SEM-EDS shows a penetration depth of a few microns and surface distribution fairly homogeneous.A fast photocatalytic activity was measured for both TiO2sol and coatings. The self-cleaning TiO2-based basic treatment does not introduce colorimetric changes compared to the untreated limestone and does not alter the properties of the stone as determined by measurements of the water capillarity absorption The basic nanocrystalline TiO2 by sol-gel processes is an easy way to obtain photocatalytic de-soiling coatings without modifying the morphology and the chemical-physical properties of limestone and ispromisingfor applications in the field of cultural heritage. Support from MAECI (project “NANO4HER, Nanotechnology at the service of cultural heritage preservation”, Italy-Israel Scientific and Technological Cooperation) is gratefully acknowledged.

Resume : A concrete is an inorganic system where amorphous silica and iron oxides react with calcium hydroxide through pozzolanic reactions that yield calcium silicates, calcium ferrites and other hydraulic phases. The rate of the pozzolanic reactions is proportional to the amount of surface area of the chemical species involved in the reactions. In order to enhance these reactions that are so important in developing the final properties of a concrete we followed the route of adding SiO2 and Fe2O3 nano-particles to the cement pastes in order to produce high performance systems. With the aim of studying the effects of the addition of nanoparticles on the behaviour of concrete and mortars, the replacement levels of cement by the solid content of the nanosilicas were 4%. The compressive strengths, tensile splitting, propagations of ultrasonic pulses, water permeability tests were investigates on different models and realistic structures by ISO EN rules. The influence of the nanoparticles on physical and mechanical properties were measured at different ripening times. Both silica and iron oxides make cement pastes harder and accelerated hydration processes of the cements themselves. A remarkable decreasing of water permeability was also observed showing that nano-concretes can be used as innovative restoration systems for cement based historical and contemporary artefacts in order to avoid carbonation processes. Moreover, a smaller quantity of cement binder inside the mortar causes relevant positive effects on the reduction of carbon dioxide emission in the atmosphere. Keywords: nanosilicas, nanoferrites, CO2 reduction, nano-addictives Altavilla, C., Ciliberto, E., 2011. Inorganic nanoparticles: Synthesis, applications, and perspectives.,CRC Press, New York Arulraj P. G., Carmichael J. M., 2011, Effect of NanoFlyash on Strength of Concrete, International Journal of Civil and Structural Engineering Vol. 2, No 2, 2011 Asuha S., Zhao S., Wu H. Y., Song L., Tegus O., 2008, One step synthesis of maghemite nanoparticles by direct thermal decomposition of Fe–urea complex and their properties. Journal of Alloys and Compounds 472, 2009, pp.123–125. Green D. L., Lin J. S., Lam Yui-Fai, Hu M.Z.-C., Schaefer Dale W., Harris M.T., 2003, Size, volume fraction and nucleation of Stober silica nanoparticles. Journal of Colloid and Interface Science 266, 2003, pp. 346-358. Jo B., Kim C., Tae G., Park J., 2007, Characteristics of Cement Mortar with Nano-SiO2 Particles. Construction and Building Materials, 21, 6, pp. 1351-1355.

Resume : We have investigated the degrading effects of various fine salt particles when deposited on the surface of artefacts painted with oil-based paints. Soiling/blackening of and deposition of inorganic, water-soluble aerosol components on the surfaces were considered. Atmospheric total suspended particulate (TSP) was actively and passively sampled by means of deployed horizontal and vertical filters in various rooms of four Belgian cultural heritage buildings, installed with various heating/ventilation systems. The inorganic composition of the deposited water-soluble TSP was quantitatively determined by means of ion chromatography. On horizontal surfaces, significantly higher chloride deposition was observed compared to vertical surfaces. Next to NaCl and NH4Cl, also the effect of the salts NaNO3/NH4NO3 and of Na2SO4/ (NH4)2SO4 was investigated. A number of model paint samples [containing inorganic pigments such as mercury sulphide (HgS, red), minium (Pb3O4, orange-red), cadmium sulphide (CdS, yellow), lead chromate (PbCrO4, yellow) and lead white (2PbCO3.Pb(OH)2, white)] were finely sprayed with solutions of these salts and dried to induce the precipitation of small salt particulates at the paint surface. These surface were artificially aged by UV irradiation in a moist environment. Near the salt crystals, combined SEM, Raman and XANES investigations revealed a more prominent alteration and local color change to have taken place at the surface of the semi-conductor pigments. Electrochemical studies, μ-XANES and μ-XRD measurements also allowed to identify some of the alteration reactions taking place. In general, since even seemingly innocuous hygroscopic salts such as NaCl can stimulate the chemical alteration of the paint surface, it appears recommended to employ state-of-the-art ventilation/air-conditions systems including facilities for trapping/filtering of (hygroscopic) fine dust particles in art galleries and musea to ensure the durable conservation of works of art.

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Resume : The glaze and in-glaze pigments of the historic nineteenth century glazed tiles from the Pena National Palace (Sintra, Portugal) were characterized using a multi-analytical approach. Chemical composition and structural characterization were ascertained by µ-PIXE, µ-Raman, Optical Microscopy and VP-SEM. The production technique and colour palette in these tiles were found to be close to the ceramic pigments used in traditional majolica. The blue and purple colours derive respectively from cobalt oxide and manganese oxide. A mixture of Naples yellow with cobalt oxide and iron oxide were used for green and dark yellow respectively while grey tonalities consist of a complex mixture of cobalt oxide, manganese oxide and Naples yellow in different proportions. Results obtained allowed for the assessment of the nature of the pigments used as well as production techniques, resorting to traditional majolica manufacture although the tiles were produced by the end of the 19th century.

Resume : The aim of this paper is to analyze the suitability of artificial neural networks to identify the different rock-forming minerals of hercynian granites from hyperspectral data. These granites are the most used rocks in the monuments of Architectural and Artistic Heritage in NW Spain. Granites consist of mineral grains with different chemical and physical properties. Therefore, in laser cleaning campaigns these minerals exhibit different behavior under the action beam which can result in undesirable damage such as the melting of biotite grains or the fracture of quartz crystals due to laser overexposure. The automatic control of the cleaning process requires the rapid and reliable identification of the minerals in the surface area to be irradiated. In order to achieve this purpose, a hyperspectral camera was used and an ANN algorithm which works with the collected spectra of the granite surface was designed. The efficiency in the correct identification of the different granite-forming mineral grains, i.e. quartz, feldspars, plagioclase and biotite was evaluated and a high degree of success was achieved. Keywords: Artificial Neural Networks, granite, hyperspectral technique, mineral identification, forming mineral, Cultural heritage.

Resume : The aim of this paper leads to the evaluation by means hyperspectral techniques of the effectiveness of the laser cleaning of a complex biogenic patina composed of lichens. Samples of a hercynian granite from NW of Spain colonized by an endolithic crustose lichen were collected and cleaned using the third harmonic of a Nd:YVO4 nanosecond laser. In addition, the effectiveness of the laser cleaning in terms of the patina extraction rate and of the damage caused on the surface was evaluated by means of a hyperspectral camera. The suitability of this non-destructive, on-line, fast and in situ monitoring technique in order to evaluate the effectiveness of the cleaning was assessed using optic microscopy, Scanning Electron Microcopy with energy-dispersive X-ray spectroscopy (SEM-EDX), Fourier Transform Infrared Spectroscopy (FTIR) and color measurements in CIELab space. These techniques were found very powerful for estimating the degree of cleaning, through the detection of traces of organic matter and the damage in granite minerals, allowing us to detect the melting in biotite or the fractures in the quartz. However they are destructive techniques and make the evaluation process longer and discontinuous. Therefore, the hyperspectral technique resulted an advantageous method to assess the effectiveness of the laser cleaning of granites in comparison with conventional techniques. Keywords: Granite, laser Nd:YVO4, lichenic patina, stone cleaning, hyperspectral technique.

Resume : Recently, organic–inorganic hybrid materials have been extensively studied, as they could exhibit bet- ter mechanical, thermal, optical, and electronic properties, compared with the corresponding pure organic or inorganic aystems. The properties of hybrid materials could be tuned through the func- tionality or segment size of each component Poly(methyl methacrylate) (PMMA) is an impor- tant thermoplastic material with excellent transpar- ency. However, its poor thermal stability restrains it from applications in higher temperature region. One possible solution to address the above problem is to hybridize with inorganic oxides such as silica or tita- nia. The sol–gel technique is often used to produce hybrid materials [1]. Inorganic-organic hybrid systems made ofpolymethylmethacrylate (PMMA) addedwithan inorganic filler based on SiO2 and ZrO2have beensynthesized, characterized and tested as coatings for the protection of sandstones, of interest for cultural heritage. PMMA was dissolved in a mixture of two accurately chosen solvents, methylethylketone(MEK) and 2,2-dimethyl-4-hydroxymethyl-1,3-dioxolane(Augeo SL 191).Tetraethylorthosilicate (TEOS) and zirconyl chloride (ZrOCl2•8H2O)were added in different ratiosasinorganic precursors. The materials obtained by the sol-gel process werecharacterized by XRD, FTIR-ATR andµ-Raman spectroscopy.The coatings were tested on two sandstone species from Tuscany (Italy): Pietra Doratafrom Manciano andPietra Serena (litarenite Arcosica) fromFirenzuola. Water absorption by total immersion and by capillarity, contact angle and color parameters of surfaces were determined, before and after the application of the synthesized coatings. The results on the water absorption and on the contact angle indicate,for both treated sandstones, an improvement of water repellency. The total color differenceintroduced by the coatings is acceptable, withoutevident modifications of the aestheticappearance. [1] H.-C. Kuan, S.-L. Chiu, C.-H. Chen, C.-F. Kuan, C.-L. Chiang, J. Appl. Pol. Sci. 2009, 113, 1959-1965.

Resume : Arsenic sulfide pigments, commonly referred as orpiment and realgar, have been used worldwide from antiquity until the 19th-century1,2,3. Throughout the time it was in use, many names have been used to designate arsenic sulfide pigments. For examples, orpin, yellow realgar, King’s yellow, arsenicon, seki have been used for the orpiment while red orpiment, sandaraque, orpin or burnt orpiment were used for the realgar1,4,5. This multiple terminology makes its description and history of use rather complex. In addition to the multiple terminology, many manuscripts mention, alongside the natural crystalline pigments, artificial forms made from alchemy6,7. Nevertheless, this artificial form of the pigment has been mostly overlooked during the photo-degradation studies of the arsenic sulfide group pigments realized until now8,9,10. The quick distinction between the naturally occurring pigment and the synthetic ones was made possible by the development of accessible techniques such as Raman spectroscopy. Investigation of arsenic sulfide particles showed in some cases that artificial arsenic sulfide is uncounted more often than one would think, even though they are not very often found in European easel paintings, maybe due to their high toxicity, price and problematic behaviors toward other pigments, especially the copper- and lead-containing ones. Nonetheless, it has been encountered in polychrome artworks in 13th to early 20th-century European and Asian works of art2. For example, it has been unveiled in 18th-century “chinoiserie”, 18th-century baroque polychrome wooden sculptures or, in higher amount in the late 19th-early 20th-century decorative panels of the Japanese pagoda from the Royal Domain in Laeken, Brussels, Belgium. In all of these artifacts, the arsenic sulfide pigments appear to be in a very good conservation state. This led us to wonder about the stability of artificial arsenic sulfide pigments. But, to study and understand the stability of artificial arsenic sulfide pigments, it is crucial to know its exact nature and composition. In that regard, we interpreted ancient recipes found in manuscripts in order to synthetized the different forms of the pigment starting with different materials. This led to pigments with various purities and characteristics which could lean toward different stabilities. This research represents the first part of an in depth degradation study of arsenic sulfide pigments aiming for a comparative study of natural and artificial arsenic sulfide pigments and the influence of the binding medium in which it is used on the degradation processes.

Resume : A major objective of all conservation treatments is to increase the physical and chemical stability of the objects being treated. Given that photographic gelatin emulsions are highly susceptible to different forms of damage such as flaking, cracking, and powdering; consolidation treatments often forms an important part of the stabilization process. The application of nanomaterials is a new approach in photograph conservation, which will hopefully enable the control of the properties of traditional consolidants thus improving their performance. In this study, gelatin nanoparticles and nanolayers were prepared and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and dynamic light scattering (DLS)for testing on damaged gelatin emulsion. Thenanolayers were prepared by a two-stepdesolvation method, in order to obtain gelatin nanoparticles, followed by a third step involving rapid solvent evaporation.The prepared particles were found to have a spherical shape with sizes varying from 33 nm to 216 nm and a mean size of 42 nm depending on the conditions of synthesis. This research showed that both pH and temperature are very effective on particle size. Further studies are being planned to evaluatethe benefits and potential problems ofin-situ consolidation of damaged gelatin emulsion using gelatin nanolayer technique. Keywords: Gelatin, nanoparticles, pH, temperature,scanning electron microscopy, transmission electron microscopy, dynamic light scattering * Endnotes This research is a part of Project SACPP No:61-12-A2 (A scientific approach to the conservation of printed photos)-Scientific and Technological Cooperation between Arab Republic of Egypt and Italian RepublicMAECI (Project ‘La conservazione degli archivi fotografici: un approccio scientifico’)

Resume : The use of nanotechnology in conservation is a relatively new concept. Usually, classical clean-up methods take into account the use of other chemicals: from one hand they help the environment destroying pollutants, but from the other they often become new pollutants. Among the new oxidation methods called Advanced Oxidation Processes (AOP), heterogeneous photocatalysis has appeared an emerging technology with several economic and environmental advantages. A new sol-gel method of synthesis of TiO2-anatase is reported in this work using Lithium and Cobalt (II) salts. The activation energy of the doped-photocatalyst was analyzed by solid-state UV-Vis spectrophotometer. The mobility of Li-ions on TiO2 NPs surface were characterized by 7Li solid-state NMR spectroscopy and 7Li NMR relaxation measurements. Also X-ray photoelectron spectroscopy (XPS) were done. Use of doped-nanotitania is suggested from authors for the removal of pollutants in confined areas containing goods that must be preserved from decomposition and ageing phenomena Keywords: Anatase, TiO2, photocatalysis, solid-state NMR, solid-state UV-Vis Altavilla, C., Ciliberto, E., 2011. Inorganic nanoparticles: Synthesis, applications, and perspectives.,CRC Press, New York Wouter J. H. Borghols,Dirk Lützenkirchen-Hecht,UllrichHaake, Wingkee Chan, Ugo Lafont, Erik M. Kelder,d Ernst R. H. van Eck,Arno P. M. Kentgens, Fokko M. Mulder, and MarnixWagemakera,Lithium storage in amorphous TIO2 nanoparticles: Journal of electrochemical society, 157 (5) (2010) I. Hung, Z. Gan, On the practical aspects of ecordingwideline QCPMG NMR spectra,Journal of Magnetic Resonance, 204 (2010) 256-265

Resume : The aim of this work is to provide a better understanding of the chemical reactions involved in the formation of the patina on shakudo, the peculiarity of its colourand to attempt to develop a method with ascientific basis for its study and recognition. Different recipes for shakudo realization have been reviewed, choosing one for its historical coherence and proven efficacy and using it for the coloring of both a pure copper sheet and a Cu alloy containingsmall amount of gold, in order to compare the different features of the pure metal and the alloy. The patinas were then analyzed with EDXD and XRD to identify the surface chemical composition; the structure of the metal was observed with SEM-EDS and Atomic Force Microscopy (AFM) to identify any morphological changes that may contribute to the surface characteristic hues. A chemical mechanism for the formation of the patina is proposed. Keywords: surface treatments, shakudo, patina, Japanese alloys

Resume : The protection of historical monuments is an issue of great interest andthe application of polymers as surface treatments is a quite common practice since these coatings form a protective layer on the surface as well as are able to prevent the salts migration from the surface to the stone. Marbles commonly employed in architecture (Carrara, Candoglia, Botticino and Angera) have been treated with both commercial water-repellent protective agents (siloxanes) and new formulated coatings obtained by mixings resins with TiO2 nanoparticles. By means of contact angle measurements the hydrophobic behavior of the treated surfaces has been evidenced. By photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) some specific characteristics of the treated marbles have been evidenced. In particular the homogeneity of the coatings has been highlighted by XPS while AFM allowed to disclose the presence of micro and nanoparticles on the coated surfaces. The color of the coated samples has been evaluated by CIE-Lab colorimetric analyses.Not significant color variations ( i.e. ΔE* < 5) were registered.

Resume : Conservation and sustainable management of outdoor metallic cultural heritage assets is a complex issue because of the high variety of the materials employed to realize complex-shaped structures and of the climate and environmental changes due to industrialization, such as the increase of air pollutants in the atmosphere. Non-invasive approaches for monitoringthe assets stability by means of in situ measurements are, therefore, important tools to be designed and improved in the next future in order to ensure the long-term sustainable management of outdoor metallic cultural heritage.These approaches have also to be based on simple easy to use and low cost arrangements in order to really wide spread theirapplication in the cultural heritage field. Among the different techniques extensively used for corrosion inspection and monitoring of metallic artefacts, electrochemical impedance spectroscopy (EIS) presents several important advantages. Firstly,EIS is an accurate, sensitive and non-destructive technique for monitoring the protective effectiveness of corrosion product layers and protective coatings, without the need of sampling the artefacts and without accelerating their degradation. Moreover, EISmonitoring campaigns can be easily repeated in different periods to evaluate the conservation state evolution and to highlight the need of restoration. Many different complete EIS systems are nowadays commercially available, which exhibit excellent performance, but are either to be used in a laboratory or have design, dimension and cost that impair their use. In this study, a new complete solution which is based on a low cost EIS system coupled with specially crafted electrodes has been used to investigate the corrosion behaviour of weathering steel assets exposed outdoor in different cities in Italy. The EIS measurement system is based on a low-cost Arduino Due board coupled with a'shield' that hostsa logarithmic amplifier,whichextends the measurement capability to impedances in the range of 100 to 1G and for a frequency range of 0.01Hz to 100kHz. Two ABS electrode types, one designed to measure on quasi-horizontal surfaces and another for vertical and quasi-vertical surfaces, have been designed and realized by means of a 3D printer. The entire systemcan be powered directly by a portable personal computer so that measurements can be performed also in the absence of power supply. The measuring campaigns in progress and the previous results obtained, put in evidencethat the proposed solution represents an interesting new tool for the assessment of the conservation stateof metallic assets, allowing the monitoring of the atmospheric corrosion evolution as a function of the exposure to the different environments.