Cultural heritage at risk - perspectives on technologies, materials, modelling and digitalization

Resume : A fresco painting mounted on a canvas by strappo technique was examined by using THz time domain imaging for future conservation planning. The advantage of THz time-domain imaging is that it can reveal internal structure non-destructively. The technique uses a narrow pulse of which frequency range reaches THz region. When a THz pulse is applied to a sample, the first reflected pulse is obviously generated by the surface, then a reflection pulses generated at internal interfaces are obtained, resulting in a pulse sequence in time domain. Since the dealy corresponds to the distance from the surface, the pulse sequence indicates internal layer structure, which are important for conservation planning. This technique is known as the time-of-flight method and is used in various other nondestructive testing techniques. Technical details of THz time-domain imaging are explained in refereneces [1-3]. The "Memories of Italy" was painted by Luka Hasegawa by buon fresco technique after his return from Italy in 1958. It was detached by the strappo techinque and was mounted on canvas. Since the back of the frame was covered by a board, the backside of the artwork is not visible. Fine threads of cloth, probably used in the strappo process, were left on the surface. There are also many places where the painting layer has been peeled off. It is likely due to shrinkage of glue that could noe be removed from the painting surface. In addition, there are a number of areas which appear to have been painted directly onto the lining canvas itself. According to those who worked with the artist at the time, he treated strappo as a process in the middle of production, rather than as a treatment after the work was completed, and he often painted over. We used a portable scanner-type THz-TDS system (Terametrix, T-Ray 5000), which has been used for more than 10 years in museums. At many observation points, the layer structure of the cross-section is not uniform and the thickness from the surface to the back of the lining canvas is not constant. Cross-sectional THz imaging revealed that some of the uneven surface areas had been raised with additional lime, while others retained the substrate of the original buon fresco painting. Experimental results suggest that, the THz imaging is useful for observing the lining of fresco paintings after strappo, in addition to wax-resin lining of oil paintings [4]. [1] D. M. Mittleman, Twenty years of terahertz imaging, Optics Express, Vol. 26, pp. 9417-9431, 2018. [2] I. N. Duling, D. Zimdars, "Terahertz imaging: Revealing hidden defects", Nature Photonics, Vol. 3, pp. 630-632, 2009. [3] K. Fukunaga, "THz Technology applied to Cultural Heritage in Practice", Springer, 2016. [4] K. Fukunaga, Y. Ueno and Y. Ito, "Investigation of Multilayered 20th Century Painting by THz Imaging," 2019 44th IRMMW-THz, 2019.

Resume : The monumental architecture of Middle Eastern cities was characterized between the 14th and 4th centuries BC by the use of colored glazed bricks. The production of this kind of decoration required thorough knowledge and important resources. The regions of production of these bricks (Assyria, Babylonia, Elam) moved throughout history between the Mesopotamian alluvial plain and the Iranian world. However, the share of knowledge and local innovations that took place in this geographical space is not clearly defined. The purpose of this research is to gather information about the brick manufacturing processes by examining the colored glazes. Among the various colors of these decorations (different shades of blue, white, black, yellow, orange, green), we focused on black glazes used to separate different glazes or to fill colored areas. In this study, a double approach was conducted in parallel. Firstly, the well-preserved glazes of 15 colored bricks representative of the decoration of the palaces of Sargon (Khorsabad, 8th century BC) and Darius (Susa, 6th century BC) were examined. Secondly, and on the basis of the latter analyses, replicas of colored glazes were synthesized in laboratory. The characterization of both archaeological and replica black glazes was performed using a combination of methods that included optical microscopy, SEM-EDX, X-Ray diffraction and µ-Raman spectroscopy. The results revealed a major change in the coloring technique of black glazes employed in the Neo-Assyrian and Persian Achaemenid periods. Regarding the black glazes of Susa, it is particularly interesting to note that the chemical composition varies according to the role of the glazes. As a matter of fact, the black coloration is obtained thanks to manganese oxide (for colored areas) and to iron-rich compounds (for relief lines separating glazes). On the contrary, the black of Khorsabad bricks is characterized by the presence of copper sulfide nanoparticles. This coloring technique is very rarely described in the literature, as well as the mechanism of formation of these spherical nanoparticles. Glazes produced under controlled conditions with different copper vectors (sulfide or oxide) and the presence (or not) of a reducing agent can give us some indications on the production techniques (recipes, firing temperature…). The data obtained recontextualized with the published data constitute a privileged tool to support hypotheses on the evolution of the production techniques of bricks craftsmen in the Middle East in Antiquity. This study was carried out within the framework of ABRIKHOS Project and supported by the Fondation des Sciences du Patrimoine (FSP).

Resume : The Knossos Palace is one of the most important archaeological sites in Greece and the second most popular tourist destination of the country, after the Acropolis of Athens. Its primary attraction is represented by the extensive restoration carried out by the site excavator Sir Arthur Evans in the early twentieth century. The necessity of restoring the Palace was evident since the first years of excavation. The fragile building materials proved to be extremely sensitive to weathering. After a first phase in which Evans took actions restricted to protect ruins, he attempted a reconstruction of the monument, with large use of reinforced concrete, being this one of the most widely used building materials. Considered to be a highly durable material, concrete was used for structural repairs, load bearing reinforcing elements and new architectural elements, often placed in direct contact with the original materials and structures. Today, Evans’s reconstruction of the Knossos Palace forms an integral part of the monument and its history to be studied and protected. In the HERACLES H2020 Project [1] context, samples of the concrete used in the Palace of Knossos were collected and analysed to assess their morphological, microstructural, and chemical characteristics, mechanical properties and their weathering status to support preservation actions. As well, the degradation of the iron bars due to corrosion was studied. For this purpose, a multi-analytical approach, i.e. the use of several analytical techniques, was considered mandatory. Advanced techniques able to detect characteristics even at sub-microns /nano-meter scale were used. Keywords: cultural heritage; concrete, iron corrosion, weathering assessment

Resume : The goldwork technology had its first substantial evolution in Western Europe during the Iron Age (IA). With the use of gold alloys with different compositions and the introduction of new technologies (such as filigree, granulation, soldering, and gilding techniques) new technical solutions and aesthetic outcomes were adopted. In this presentation, a Late Iron Age earring from the Northwest region of the Iberian Peninsula will be presented taking into account the alloys and technologies used at that time. The earring has a complex structure, with the presence of twisted wires and granulation. Characterization by digital optical microscopy, portable energy-dispersive X-ray spectrometry (XRF) and micro-XRF were performed to study its composition and its manufacture. Results show that the earring is constituted by two different alloys: a core in a silver-rich alloy and an external coating of gold-silver-copper ternary alloy. This is a rare example of a gilded earring in Late Iron Age in Western Iberia, and shows that the use of different technological solutions were adopted by this time, being attained distinctive mastery of goldwork. In this presentation the manufacture reconstitution of the earring will be presented considering the actual state of knowledge of the gilding techniques, alloy compositions and manufacture solutions of Iron Age goldwork at Western Europe.

Resume : Bronze artifacts constitute a fundamental portion of Cultural Heritage, but effective methodologies for the removal of corrosion layers, such as those produced by the “bronze disease”, are currently missing. We propose the formulation and application of novel poly(2-hydroxyethyl methacrylate) (pHEMA) networks semi-interpenetrated (SIPN) with poly(acrylic acid) (PAA) to achieve enhanced capture of copper ions and removal of corrosion products. The pHEMA/PAA SIPNs were designed to improve previous pHEMA/poly(vinylpyrrolidone) (PVP) networks, taking advantage of the chelating ability of pH-responsive carboxylic groups in PAA. Increasing the pH ionizes carboxyls, increases the porosity in pHEMA/PAA, and leads to the co-presence of enol and enolate forms of vinylpyrrolidone (VP), changing the macroporosity and decreasing the mesh size in pHEMA/PVP. The ion−matrix interaction is stronger in pHEMA/PAA, where the process occurs through an initial diffusion-limited step followed by diffusion in smaller pores or adsorption by less available sites. In pHEMA/PVP, the uptake is probably controlled by adsorption as expected, considering the porogen role of PVP in the network. Upon application of the SIPNs loaded with tetraethylenpentamine (TEPA) onto corroded bronze, copper oxychlorides dissolve and migrate inside the gels, where Cu(II) ions form ternary complexes with TEPA and carboxylates in PAA or carbonyls in PVP. The removal of oxychlorides is more effective and faster for pHEMA/PAA than its /PVP counterpart. The selective action of the gels preserved the cuprite layers that are needed to passivate bronze against corrosion, and the pH-responsive behavior of pHEMA/PAA allows full control of the uptake and release of the Cu(II)−TEPA complex, making these systems appealing in several fields even beyond Cultural Heritage conservation (e.g., drug delivery, wastewater treatment, agricultural industry, and food chemistry).

Resume : The Sydney Harbour Bridge is a heritage-listed steel arch bridge with massive granite-faced pylons crossing Sydney Harbour and will celebrate this year its 90th anniversary. The Bridge is recognized as a symbol of Australia and is a vital part of Sydney’s transport infrastructure with more than 200 trains, 160,000 cars and about 2,000 bicycles crossing the Harbour every day. Maintaining the Bridge requires a tremendous effort, and the current conservation work involves sandblasting but many restrictions and challenges make the process difficult. Lasers have been used extensively for the conservation of heritage materials in the last 30 years to remove a wide range of unwanted encrustations. Laser ablation does not require the use of chemicals or abrasives, thus eliminating problems of chemical toxicity, corrosive residues, and erosion or loss of surface detail. With the recent advancement in laser technologies, laser cleaning is now a capable tool to treat historic surfaces in a way not possible with any other method. Current laser cleaning systems used in conservation operate with nanosecond or longer pulse durations, which involve the evaporation of surface layers or removal of chunks of materials with the generation of shock waves and the propagation of heat. This ablation mechanism can potentially modify the morphology and structure of the underlaying substrate and induce undesirable side-effects. The development of powerful ultrashort pulsed lasers has opened up new possibilities to clean encrusted surfaces without heating the substrates. Those lasers use pulses in the picosecond and femtosecond range and are able to break molecular bonds with minimal heat load, in a process called “cold ablation”, inducing minimal damage to the underlying layers. The Sydney Harbour Bridge is a unique application of ultrafast laser for the conservation of cultural heritage. We explored the treatment of the Australian Moruya granite, made of quartz, plagioclase, potassium-feldspar, biotite, and hornblende, used in the cladding of the pylons with a femtosecond pulsed laser. We studied the removal of surface contaminants commonly found on the stone surfaces of the Bridge while keeping the laser energy under the damage threshold of the stone. The effects on the treated surfaces and the cleaning efficiency were assessed using multiple analytical methods including optical and scanning electron microscopy, profilometry, and vibrational spectroscopy. We demonstrate efficient cleaning results in a damage-free and abrasion-free treatment, illustrating the advantages of ultrafast lasers for the conservation of cultural heritage.

Resume : A significant part of the memoirs of the 20th century was recorded in films, photographs and audio tapes made with cellulose acetate (CA) that need to be preserved. A new methodology in evaluating the current degradation state of a historical films along with its evolution over time will be presented. The developed methodology is based on hybrid modelling to serve as a practical tool for conservators to assess films conservation state and to design storage and conservation policies that are best suited for each cultural heritage film. The hybrid model approach consists in a first-principles model to describe the degradation mechanisms of the CA pure polymer [1] coupled with two data-based (machine learning) models that describe the degradation behaviour of historical films in relation to the pure polymer [2]. In the first principles model, the reaction mechanisms were investigated using electronic Density Functional Theory calculations to determine the energy barriers of the degradation reactions. This information was coupled with the Transition State Theory to establish the long-term degradation kinetics. The data-based models resource on films’ descriptors as well as sensor data that monitors degradation by measuring acetic acid emission (the main degradation product) to provide predictions on film’s degradation behaviour. The hybrid model solution integrates the effect of main storage parameters (temperature, humidity level, mass of the film, box volume) as well as the effect of acetic acid adsorbers in case present, while taking the specificity of each historical film into account. It provides the user all the quantitative information on the effect of each preservation action that is needed so that the best decisions can be taken. The developed tool gives the user confidence and guidance to take the best conservation actions based on informative predictions, for energy saving and extended conservation time. [1] A. Al Mohtar, S. Nunes, J. Silva, A.M. Ramos, J. Lopes, and M.L. Pinto. "First-Principles Model to Evaluate Quantitatively the Long-Life Behavior of Cellulose Acetate Polymers." ACS omega 6, no. 12 (2021): 8028-8037. [2] Al Mohtar, Abeer, Moisés L. Pinto, Artur Neves, Sofia Nunes, Daniele Zappi, Gabriele Varani, Ana Maria Ramos et al. "Decision making based on hybrid modeling approach applied to cellulose acetate based historical films conservation." Scientific Reports 11, no. 1 (2021): 1-13.

Resume : The cleaning of Modern and Contemporary paintings requires particular care: traditional methods are too invasive and risky for their clotted, water-sensitive surfaces, where mechanical action and spreading of free solvent should be avoided. The ideal systems for the task are highly adaptable and retentive gels, with a macroporous structure that allows the diffusion of cleaning fluids throughout the gel matrix and at the gel-substrate interface. Micron-sized pores with different morphologies can be obtained by mixing polymer pairs that undergo phase-separation in aqueous solution. In this light, we prepared cryogels by combining a highly hydrolyzed Polyvinyl Alcohol (H-PVA) with a partially hydrolyzed PVA (L-PVA), and a poly(vinyl pyrrolidone), PVP. The polymers were fluorescently labeled, and the systems morphology at the microscale was observed through Confocal Laser Scanning Microscopy (CLSM). In both H-PVA – L-PVA and H-PVA – PVP pre-gel solutions, liquid-liquid demixing occurs. In other words, L-PVA and PVP spontaneously concentrate in micron-sized blobs, while H-PVA remains in the continuous phase. L-PVA and PVP blobs act as templates during the freezing process: when the thawed gels are finally stored in water, the polymers are partially washed away, leaving pores in the structure. However, L-PVA and PVP play also other roles during the gel formation: they alter H-PVA chains self-interaction and ability to crystallize, influencing the gels structuration and rigidity. L-PVA and PVP also affect the gels characteristic dimensions at the nanoscale, the gel point and the gelation mechanism. Small Angle X-ray Scattering (SAXS) and Differential Scanning Calorimetry (DSC) gave insights about the correlation lengths and the crystallites size in gels containing different polymer concentrations. The gelation mechanism was investigated through rheology, and the characteristic exponents were compared to De Gennes’ scaling laws derived from percolation. Finally, Nuclear Magnetic Resonance (NMR) was used to quantify the residual L-PVA and PVP after washing, highlighting how the nature of the gelation process varies depending on the porogen type. Overall, both L-PVA and PVP behave as porogens and structuring agents, but differently: polymer-polymer interactions in the pre-gel solutions, polymers hydrophilicity and physico-chemical characteristics are crucial to determine the final cryogel features and cleaning performances.

Resume : The deterioration of museum collections due to air pollution and uncontrolled atmospheric conditions is a well-known fact. However, the detailed processes that promote the degradation of specific materials remain largely unknown. Thus, it is necessary to carry out a rigorous study of the correlations between types of materials exposed in museum collections and air pollutants to prevent or minimize the degradation process of museum artifacts. One of the less studied pollutants are volatile organic compounds (VOCs). VOCs include a large family of gases that share common characteristics, such as high vapor pressure and low water solubility, but may differ considerably in terms of effects. The level of all VOCs (TVOC) is typically used as an indicator of overall air quality. Nevertheless, TVOC has not been linked to any certain material damage, while some specific VOCs can be linked to it. Aldehydes and organic acids, such as formaldehyde and formic acid, are the main organic carbonyl pollutants of potential concern for cultural heritage. Per se, there is a high interest in the development of monitoring systems to discriminate and quantify different VOCs. In fact, these systems are the first step to identify and reduce, or even eliminate, their emitting sources to mitigate their adverse impact on cultural property. Despite this, commercially available, reliable, cost-effective, and easy-to-use gas sensor technologies for individual VOCs monitoring are lacking. With this aim in mind, we have developed a portable electronic nose based on a single sensor for quantification of selected VOCs of interest in the framework of the SensMat project. The prototype here presented has an intuitive software and wireless long range data transmission that, via cloud-based solutions, allows to evaluate the concentration of VOCs of interest in near-real time. These features allow non-expert users, such as museum curators, to easily monitor the concentrations of the target pollutants from their own personal electronic devices. The developed sensor system can monitor formaldehyde, formic acid, and acetic acid in the measurement range 150 to 3000 parts per billion and can be adapted to work under different levels of relative humidity, from 5 to 65%. The system presented is equipped with an innovative sensor housing that has been designed and 3D printed for a proper air supply and ambient light screening of the gas sensor. Thanks to multivariate statistics and dynamic operation, the developed monitoring system avoids manual data collection and post-processing of data, which is very convenient for non-expert users. In conclusion, this automated VOC monitoring system offers museum and facility curators a proactive solution that can help to identify emission sources alongside mitigate cultural heritage deterioration.

Resume : The development of affordable VOCs adsorption materials having low environmental impact and high VOCs adsorption capacities is still an open challenge. Herein, a novel organic-inorganic composite system for the removal of acetic acid, made of zinc oxide supported and incorporated on a polyurethane derived from castor oil is described. According to the literature, a similar approach of designing an environmentally friendly compact hybrid organo-inorganic system for the efficient and stable adsorption/absorption of acetic acid hasn?t been reported yet. A biomass-derived castor oil polyurethane made of castor oil and poly(hexamethylene diisocyanate) was employed as sustainable polymer having acetic acid absorption properties, while low toxic and cheap ZnO was employed as acetic acid remover through the formation of zinc acetate. The synthesis of ZnO/COPs was proved to be environmentally friendly basing on different green metrics and easily scalabe up (up to kg-scale). A sequence of ZnO-castor oil polyurethane composite systems (denoted ZnO/COPs, where COPs stays for ?Castor Oil Polyurethane?) was thus prepared using three types of ZnO powders, having different particles size distributions, ranging from 20 nm to 44 µm and different commercial availabilities. The adsorption capacities of ZnO/COPs were studied by carrying out adsorption tests in small sealed chambers in saturated atmosphere of acetic acid (AcOH) followed by desorption under vacuum. In addition, the adsorption capacities of ZnO/COPs were investigated in 54 L glass reactors at low (ppmv scale) concentration of AcOH and in a 630 L wooden box naturally releasing acetic acid. The novel materials were fully characterized by infrared spectroscopy, thermogravimetric analysis and SEM images before and after the adsorption tests. The adsorption capacities obtained in the test in saturated atmosphere of AcOH demonstrated that ZnO/COPs could adsorb up to 0.75 g of AcOH per g of material while commonly employed activated charcoal could adsorb 0.2 g of AcOH per g of material. Best ZnO/COP sample could break down 97% of AcOH concentration when exposed to a ppmv starting concentration of the pollutant (in the 54 L reactors) while it could halve the AcOH concentration in the 630 L wooden case. The results also demonstrated a synergistic effect between the polyurethane structure and ZnO for the adsorption of AcOH.

Resume : In 2020, the European Synchrotron Radiation Facility (ESRF) was upgraded to become the ESRF-EBS (Extremely Brilliant Source), resulting in an increased brightness and coherence of the synchrotron beam [1]. This boosts beamlines performance, in particular in terms of speed and motivates the development of new access models, as an alternative to the standard 2-pages peer-reviewed proposals which offer beamtime to a single group and a single experiment. Three pioneer projects were successfully submitted in 2021, among which the block allocation group (BAG) for structural investigations of historical materials. Within the Heritage BAG, different projects are grouped together under the requirement that they all need structural information obtainable by X-ray powder diffraction at the ESRF, either through high-angular resolution XRD at ID22 [2] or high-spatial resolution 2D µXRD imaging at ID13 [3]. Through the BAG, regular access to ID22 and ID13 (once every 6 months) is provided for a 3-year period (2021 - 2024) to all the partners. As of today, 11 research groups from 6 European countries are collaborating in the Heritage BAG (ENS Paris Saclay; the Rijksmuseum, Amsterdam; TU Delft; CNR-SCITEC, Perugia; Courtauld Institute of Art, London; Politecnico di Milano; Centre de Recherche et de Restauration des Musées de France, Paris; Universitat Politècnica de Catalunya, Barcelona; Institut de Recherche de Chimie de Paris, Paris; University of Antwerp and the ESRF) [4]. While they all work on different projects, on various ancient materials (pigments, paintings, ceramics, wooden artifacts, remineralized textiles?), they all share an identical analytical need for state-of-the-art structural information. The BAG structure makes more efficient the beamtime allocation process and allows an increased synergy between ?expert? synchrotron user groups and new groups, thus creating a new scientific network structured around the ESRF, fostering new European collaborations, and finally resulting in an important scientific output. This communication will present the BAG functioning in more detail, provide specifications on the analytical configurations accessible, and introduce some research cases already tackled within the first six months. The objective is to highlight how this new collaborative access mode provides an easier, more efficient access to synchrotron capacities to our community and to encourage new groups to join this collaborative venture. [1] https://www.esrf.fr/about/upgrade [2] V. Gonzalez et al., Anal. Chem. (2017) 89(24): 13203 [3] V. Gonzalez et al., Angew. Chem. (2019) 58(17): 5619 [4] https://www.esrf.fr/BAG/HG172 The Heritage BAG is supported by the Streamline project, Horizon2020 funded project (INFRADEV grant agreement No 870313).

Resume : Historic glass recipe documents offer a precious source of information on the evolution of chemical and material sciences and their relationship to glassmaking. This research aims to create new knowledge based on the link between historic documentary information on glass production and historical objects produced. Representative recipes of glass-based paints, such as yellow silver staining, are being selected from treatises and recipe books and reproduced in the laboratory. Yellow silver stain appeared between the late 13th and early 14th centuries and was first described by Antonio da Pisa. It consists of applying a mixture of silver salts with an aluminosilicate (clay or ocher) on a glass substrate, followed by a thermal treatment, where silver ions diffusion and nanoparticles formation occurs. The clays promote the reduction reactions of silver on the glass surface during the annealing and facilitate the exchange with the alkali ions . After firing, a yellow coloured layer is obtained by forming silver colloidal particles inside the glass substrate. The produced colour depends on several properties and reactions related to the glass substrate and paint composition and also with the time and annealing temperature. A deeper knowledge of the nanoparticles formation process and occurred reactions is fundamental for discovering new information and insights into the history and conservation of our material culture, impacting its preservation, interpretation, and appreciation. This study was centred on the analysis and reproduction of recipes found in historical treatises to better understand the yellow stain production processes. The analysis of treatises resulted in the collection of different recipes from the 14th to the 19th century. Ten recipes were selected and their viability to produce satisfactory results was tested. The characterisation of the reproduced recipes was done by UV-Vis Absorption and Reflectance Spectroscopy, Particle Induced X-ray Emission and X-ray Diffraction. These analyses allow us to comprehend the difference in tones obtained, relating those with the paint compositions and production conditions. Finally, the results are being correlated with historical glass paints applied on stained glass, aiming to understand how this historical written information represents the practices at the stained-glass workshops. K. C. Barley, «Tests et observations à propos de l’usage du jaune d’argent», em Dossier de la Commission Royale des Monuments, Sites et Fouilles, 3, 1996, pp. 117–122

Resume : In this study, Transient Absorption (TA) spectroscopy was exploited to explain the process which causes the darkening of Red Vermilion, a famous pigment known also as cinnabar. The optical properties involved in the process are studied in pure HgS and chlorine doped HgS samples, before and after exposure to UV light (365 nm). The characterization started from high-resolution Raman spectra, Reflectance, and detailed colorimetry analysis. The TA study was carried out with particular attention on the ground state bleaching signals, directly connected to the formation of intra-gap trap levels responsible for the pigment degradation. First derivative reflectance spectra reveal the presence of these defectivities, while the analysis of Tauc plots from Kubelka Munk function confirms the reduction of energy band gap due to UV exposure. Transient Absorption turns out to be an important tool of diagnosis about the conservation state of pigments applied in the field of Cultural Heritage.

Resume : Inspired by the techniques of the ancient Flemish masters, French Fleury François Richard's (1777-1852) artistic practice for coloring his paintings consisted of developing a stack of translucent layers of pigments dispersed in organic binders deposited on an opaque layer of white primer. This technique is called the oil glaze method, whose paternity was given to the van Eyck brothers at the beginning of the 15th century. The light passes through the multiple layers by diffusing the color and reflects on the white background: an impression of depth emanates from it. The intensity of the hues increases with the number of translucent colored layers that are deposited. The effect can be compared to that of translucent glass or enamel. The optical effect is effective, because each dispersed pigment has a large effective diffusion cross-section. Hence, the recognition of Fleury Richard, famous in his time, is partly based on the rediscovered techniques of the ancient Flemish masters but also on the use of new colors produced by chemistry such as Prussian blue discovered at the beginning of the 18th century, or Scheele's green invented in 1775. Centuries later, the complex architecture of the glaze-based painting is a challenge for non-destructive spectroscopic analysis methods. Indeed, the thick white lead-based sublayer, that is highly reactive in XRF for example, may hide the signals from the translucent layers of a few tens of micrometers with a small quantity of pigments. Moreover, the nature of the used pigments, organic/inorganic, the pictorial layers and their mixing complicate the analysis of the detected signals. Finally, the outer layer of varnish may modify the spectral reflectance of the underlying pictorial layers. At the Musée des Beaux-Arts de Lyon, the pigments used by Fleury Richard have been preserved intact in a dedicated piece of period furniture which allowed us to analyse them by different methods: XRF, XRD, Raman, FTIR and UV-Vis absorption. Besides, thanks to the access to the artist’s paintings, in the same Museum, analyses of the pictorial works were performed using non-destructive methods: X-ray fluorescence and colorimetry for instance. Analysis of the obtained results correlated to those of the pigments allowed to evaluate the potentialities of the non-destructive analytical methods on the artist’s paintings. In addition, this collection of pigments enriches the knowledge of Fleury Richard contemporary painters’ practices, the contribution of chemical industry of the time to artistic creation, the pigments commercial exchanges at that time and the environmental conditions of the art workshops at the turn of the 19th-century, just before the appearance of the lead paint tube and the industrialization of color manufacturing.

Resume : Cadmium yellow degradation is a famed problem of impressionist painting, and it includes chalking, lightening, flaking, spalling, and, in its most advanced cases, the formation of a crust over the original yellow paint. However, although it is a known phenomenon, the process is still not totally understood. In order to explain the degradation process, several mock-ups were made on two hues of CdS pigment, yellow and orange. The realized mock-ups include pigment mixed with water, pigment mixed with oil, and pigment spread on canvas with linseed oil. All of them were altered through UV exposure for different time intervals and the mock-ups composed by pigments and water were degraded also by a thermal treatment. The last treatment was conducted in air using a temperature range of 300-500°C for several hours. The induced variations were analyzed with different techniques: the chromatic variations with reflectivity and with the subsequent calculation of relative CIE coordinates; the formation of degradation products with Raman spectroscopy, SEM-EDX and XRD techniques; in addition we carried out a careful analysis of the optical processes artificially induced by the formation of vacancy or trap states by means of time-resolved luminescence and transient absorption. The color that has been altered the most by both processes has been found to be the yellow pigment, with the final formation of sulfates and oxides confirmed by various techniques and accompanied by the possible presence of cadmium vacancies.

Resume : The preservation of brittle and fragile paint surfaces is undoubtedly one of the most significant issues in contemporary and modern art, both for their technical and optical properties, as well as their aesthetic values. Artists' unfettered experimentation with painting techniques and additive-rich paint formulations have led to artworks with weak powdering surfaces exacerbated by severe climatic conditions and outdoor pollution. As a matter of fact, current conservation practice lacks adequate strengthening methodologies, and traditional consolidants can alter the optical properties and water permeability of painted surfaces. Herein, a new starch-based nano-structured consolidant was synthesized to boost penetration into the porous paint layers and avoid aesthetic alterations; the large surface area of the starch nanoparticles (SNPs) is abundant with -OH groups, promoting adhesion to pigments. The SNPs were formulated through a bottomup approach, where gluten-removed Jin Shofu wheat starch was gelatinized and then precipitated in a non-solvent. Wheat starch's low gelatinization temperature is most likely crucial in favoring disassembly in alkali and re-assembly in non-solvent. The synthesis conditions can be fine-tuned to produce amorphous SNPs with an adequate polydispersity and dimensions of around 50 nm. Once redispersed in an aqueous phase, SNPs form nano-sized gel-like fractal domains by the organization of smaller units in polymer-rich and deficient regions as observed with Cryogenic Electron Microscopy. Additionally, by means of infrared spectroscopy, X-ray diffraction, and calorimetric measurements, the amorphous nature of the SNPs was revealed. Short and mobile gluten-removed starch chains, obtained after gelatinization, assemble quickly by non-solvent precipitation, forming disordered, rather than crystalline, nano-structures. Finally, aqueous and hydroalcoholic SNPs dispersions were satisfactorily tested as consolidant on artificially aged painted mockups that mimic degraded modern and contemporary painting surfaces. The efficacy of the consolidation was assessed using an in-house protocol: the SNPs penetrate across the paint section and significantly boost pigment cohesiveness, maintaining the painted layer's original optical properties, while bulk starch dispersions merely accumulate on the paint surface generating superficial rigid and glossy films. Overall, SNPs are an excellent example of how biopolymers and renewable sources can be used to create colloidal structures that can improve the resiliency of Cultural Heritage to degradation processes, favoring the transfer of works of art to future generations.

Resume : Polymeric adhesives are broadly used in as adhesives and laminating agents in conservation of glass and in preservation of outdoor architectural and monumental stone. They have found use as injection grouts for filling cracks, as well as consolidants for porous, fragile deteriorated stone. In numerous other applications, these materials are used as surface coatings, as casting media, as laminating agents (artwork, sports equipment, furniture and musical instruments), as well as matrices in polymer composites. In most of these applications, yellowing is seen as a highly negative trait. In this case study, yellowing is investigated from a mechanistic standpoint, looking into molecular origins of epoxy and polyurethane environmental aging.

Resume : Historical silk objects constitute an important portion of our cultural heritage, but their degradation produces fibers’ fragility, endangering their preservation. Traditional adhesives or repairs can lack effectiveness or physico-chemical compatibility to the aged fibers; alternatively, we show that dispersions of fibroin and composite fibroin-cellulose nanocrystals (CNC) can recover the mechanical properties of fragile, aged silk. Self-regenerated silk fibroin (SRSF) produces films at controlled crystalline/amorphous content tuning the protein concentration, and amorphous films increase the flexibility of aged silk when they are cast between the fibers. In the composite dispersions, CNC boosts the assembly of fibroin at the nanoscale, and promotes crystalline structures (α-helices) even at low fibroin concentration; the composite formulations provide even better mechanical performances to the aged silk fibers than the single components (SRSF, CNC). Overall, these formulations represent new promising and sustainable systems for the conservation of historical textiles, utilizing renewable materials (cellulose and silk scraps) to restore artifacts.

Resume : The conservation of architectural heritage is a primary concern for the preservation of the cultural identity of a population and of the tangible proofs of historic architectural development. In most of the cases, architectural artifacts must be protected over time from all the threats that could derive by both the variation of inherent properties, as the aging of the constituent materials, and external actions, such as natural hazards and strong events, typically earthquakes. The preservation of architectural heritage against seismic events requires an in-depth knowledge of its dynamic properties, which can be affected also by local damages and material degradation. In this work, the experimental tests carried out on the tabernacle of the church of Santa Maria Maggiore in Spello (Italy) for the estimation of its dynamic properties are presented. The tabernacle, made of caciolfa stone, has been built at the beginning of the 16th Century and is characterized by four columns of about 3 meters high, supporting four stone arches on which a hemispheric dome rises, reaching a total height of about 8 meters. In plan the structure has a square regular shape, with each side of about 4 meters length. The architectural artifact has been built by connecting stone elements through internal iron bars, resulting in a multi-block structure with a complex dynamic behavior. Ambient Vibration Tests (AVTs) have been carried out through high-sensitivity uni-axial accelerometers placed at the base of the columns, at the base of the arch and at the base of the dome. A total of 24 channels divided in three different setups have been recorded through a National Instrument acquisition system with a sample rate of about 1650 Hz. The dynamic identification procedures, developed in frequency and time domains, have allowed to estimate the first natural frequencies and the related mode shapes of the structures, highlighting the complex behavior of such systems, which modes are characterized by polyline shapes with tangent discontinuities placed in correspondence to the joints of the stone elements. The results, also strengthened by the outcomes derived by different nondestructive tests carried out about 20 years ago on the constituent materials, which emphasized the degradation state of the stone material corresponding to the most stressed areas of the joints, have highlighted the crucial role of diagnosis with a multidisciplinary approach in order to achieve proper decisions of interventions in the respect of the cultural heritage.

Resume : The World Heritage Committee has listed uncontrolled pollution as a major danger to cultural heritage. Therefore, it is crucial to control key indoor environmental parameters to protect cultural properties and reduce the threats to cultural values. Main known factors that degrade museum artifacts are temperature, relative humidity (RH), light, and pollutants. Even more, it has been demonstrated that the combination of some of these factors, specifically high RH together with certain volatile organic compounds (VOCs), accelerates the degradation process of sensitive materials. Nevertheless, many of the commercially and cost-effective available gas monitoring technologies suffer from a masking or saturation effect when RH is present, i.e., the concentrations of the gas of interest monitored are wrong. This fact is due to the large difference in concentrations of these two parameters that can be found in the environment, being RH present in percentage while the gases of interest range from some parts per billion to few parts per million. For this reason, we have developed a methodology that provides an effective path to overcome problems related to RH saturation with chemical gas sensors in the framework of the SensMat project. The main goal is to enhance sensitivity and selectivity towards the pollutants of interest. To achieve this objective, we operate the sensor as an array of virtual sensors using customized temperature cycles. Thanks to a data treatment algorithm, the data points of the optimal working temperature are gathered and evaluated. We demonstrate that the sensitivity of the tested sensors operating in temperature cycles towards VOCs, in this case, formaldehyde, acetic acid, and formic acid, is enhanced between 2 and 10 times with increasing RH percentage (from 10 to 60%) compared to their sensitivity when they are operated at a constant temperature, under the same conditions. The strategy here presented allows to cost-effectively enhance the performance of chemical gas sensors without any modification of the sensor itself with significant improvement of performance of the monitoring systems used to control the surrounding environment, and, therefore, mitigation of adverse impacts on cultural properties.

Resume : Marking of items is relevant to prevent illegal circulation of cultural heritage objects and objects of high value. Luminescent marking allows implementing a number of requirements for secrecy, uniqueness, protection against forgery. One of the requirements is related to the durability of luminescent markings in various environmental conditions. In this research we studied the influence of tropical climate and environmental factors specific to Southeast Asia on the stability of the luminescent characteristics of marking compositions deposited on various materials: metal, wood, ceramics, plastic, paper. Inorganic phosphors YAG:Ce, ZnS:Cu, ZnS:Sn:Sc and organic-inorganic hybrid materials based on 8-hydroxyquinolates: (CaF2+Liq), (Alq3+ H3BO3), (Liq+ H3BO3) and (Hq+ H3BO3) were used as luminescent components of the marking compositions. Phosphors were dispersed in isopropanol and thoroughly mixed using an ultrasonic bath. The resulting suspension was poured into a capillary felt-tip pen and drew the image on different materials The research was financially supported by the Ministry of Science and Higher Education of the Russian Federation within the FSSM-2020-0005 project.

Resume : Mortars can assume different functions in a building and generally they have distinct properties depending on their function. The characteristics of these materials depend on several factors, including the type of binder and aggregates used, their proportion and mixture, the application, and all environmental conditions, both physical and chemical, factors that occur after drying, carbonation and aging time. Mortars with structural and protective functions, used in block and renders are particularly studied in historical context, because they are more often exposed and accessible. Furthermore, mortars with these functions have a more evident impact on the preservation of buildings. Historic paving mortars are less common because they imply the removal of the original pavement and are therefore less accessible. In this context, this work* represents a unique opportunity to study the paving mortars, coming from the Monastery of Alcobaça. The Monastery of Santa Maria de Alcobaça is one of the most important monuments in Portugal and has been on the UNESCO World Heritage list since 1989. Founded in 1153, from the donation of a vast territory by King Afonso Henriques to St. Bernard of Claraval, the monastery was built in the likeness of the Clairvaux Abbey in France, being the first Gothic building constructed in Portugal. It obeys to the architectural austerity and Cistercian rules regarding the absence of decorative elements. The church was consecrated in the 13th century and during the following centuries there were several works of expansion of the monastery and decorative elements, being highlighted by the baroque additions, present in the current main façade of the church. In the 1930s and 1940s restoration interventions were developed to restore the church's original architectural features. During these works, ceramic glazed tiles were found, covering the head of the church. This pre-existing pavement was under the stone slabs used as cladding at that time. The ceramic tiles were considered additions of the 18th century, and therefore were removed. Recent studies suggest that these pavement ceramic tiles were the original ones from the 13th century. Currently stored in reserve, part of the collection still contains portions of laying mortars adhered to the back and sides of the tiles. The samples were collected in these areas, in different medieval ceramic pieces that made up the floor of the church. For this study, a multi-analytical approach was adopted, and results to be presented will include optical microscopy (OM), X-ray fluorescence (XRF), X-ray diffraction, Fourier-transform infrared spectroscopy (FTIR) and ?-Raman, to establish the chemical-physical and mineralogical characteristics of these mortars. *This work was supported by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT-Portuguese Foundation for Science and Technology under the project ref. UIDB/50025/2020-2023 and, SFRH/BD/145308/2019 (F. Carvalho).

Resume : The Aqueduct of Carthage was built in the 2nd century, between 128-162 A.C., by order of the Roman Emperor Hadrian. The aqueduct captured the water from two main sources, one in Zaghouan and the other in Aïn Jouggar. A third source of capture, in Aïn Djour, was also connected to the main channel. The aqueduct supplied the city of Carthage and some localities of its route, bringing water to public fountains, the thermae and some private properties. In total, it was 132 km long, having underground parts and approximately 17 km aerial zones, over arches, which reached more than 30 meters high in some stretches. It was the largest extension aqueduct built in the Roman Empire. Carthage became one of the main cities of the empire and during the following centuries went through several periods of territorial dispute. The aqueduct was attacked at various historical moments, some parts having been destroyed and rebuilt in the Byzantine period and the Middle Ages. From the 17th century until today, the aqueduct underwent several restoration interventions and reconstruction areas. Previous studies suggest that the stones used in the construction are of local origin, with emphasis on limestone of diverse geological formation. However, in relation to mortars, the monument itself is a witness to a wide variety of materials, visibly different, but which may present characteristics typical of a certain construction period or even some more traditional technique of preparation and application. Thus, the characterization of the mortars of the aqueduct is fundamental for understanding the history of the monument. Results to be presented include the characterization of a set of samples collected along the aerial zones of the aqueduct, to perceive their similarities and differences, to relate them, if possible, to the constructive or intervention period. In this first approach non-destructive analytical techniques were chosen such as optical microscopy, X-ray fluorescence (XRF) and X-ray diffraction (XRD) to determine the morphological characteristics, chemical composition, and mineralogy of the samples. This work was supported by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT-Portuguese Foundation for Science and Technology under the project ref. UIDB/50025/2020-2023 and, SFRH/BD/145308/2019 (F. Carvalho).

Resume : During the second half of the 19th century, fabrication of ceramic pieces decorated with polychrome relief glazes occupied a prominent place in French factories of white earthenware. It is through the example of the production of the Vieillard and Co. Manufactory (Bordeaux, France, 19th century) that we will approach the technical study of this decoration process. A preliminary step towards the non-invasive study of objects in the museum's collections was taken through the study of archaeological sherds of this manufactory. Multianalytical methods were carried out in order to characterize both the clay support and the colored glazes [1]. The aim of this paper is to implement a non-invasive approach of colored glazes study to characterize colored glaze and more specifically to identify the types of pigments used. This methodology is based, for the first time to our knowledge for ceramics study, on the development of optical techniques, both reflectance spectroscopy and hyperspectral imaging. A corpus of some pieces of polychrome glazed earthenware and decorated porcelain from Musée d’Aquitaine and Musée des Arts Décoratifs et du Design (Bordeaux, France) has been considered here. The selected pieces, representative of Vieillard and Co. decorative production, have a wide variety of colors. Twenty pieces, among them four color charts, were non-destructively analyzed in situ using a hyperspectral imagery system. In order to interpret bands observed on the spectra obtained, some pieces were analyzed by PIXE-PIGE. Moreover, this quantitative analysis allows us to make assumptions about the glaze recipes which are not well known from the written archives. The data obtained made it possible to better understand the nature of the decoration chromogens and thus, to establish the color palette of the artists who produced this kind of decorative objects. The goal is therefore to improve the database already established on hyperspectral imaging based on studies carried out on archaeological sherds and enriched by data acquired on color palettes. [1] Beauvoit E., Cantin N., Sireix C., Marache V., Chapoulie R., Ben Amara A., 2019. A multianalytical approach for the study of colored glaze decoration: the case study of Vieillard and Co. Manufactory (France, 19th century). TechnArt, Bruges, Belgium, 7-10 May 2019. This research is supported by the Nouvelle-Aquitaine Region, the LaScArBx (Bordeaux Archaeological Science Cluster of Excellence), ANR-10-LABX-52, the CNRS and Bordeaux Montaigne University.

Resume : Starting from the important set of archaeological ceramic remains from Gharb al-Ândalus preserved in the Municipal Museum of Archaeology of Silves, the present study intends to deepen the existing knowledge about the Islamic Ceramics of the Algarve (South of Portugal) territory during its Muslim occupation (8th-13th century) (Torres and Macías 1992; Gomes 2002-11). Based on the technologies currently available for the scientific study of Heritage, the archeometric investigation, through the material characterization of these testimonies from Silves, will allow to conclude about the materials, production techniques and their evolution over the different periods of Islamic occupation, namely the Ommiad (8th-9th c.), Caliphal (10th-11th c.), Taifa (11th c.), Almoravid (12th c.) and Almohad (12th-13th c.) periods (Ferreira et al. 2016). Furthermore, the knowledge of high-medieval Algarve ceramic objects will allow us to conclude about eventual technical differences and commercial exchanges in the territory of the Gharb al-Ândalus, using their comparison with others, their contemporaries, from regions with an important Islamic presence, such as Lisbon, Mértola and Santarém, in Portugal, and also from several important cities in Spain, as Cordova, Madinat al-Zahra and others. In the present poster, we intended to show the numerous different typologies of ceramic utensils existent in the entire chronology of Islamic occupation of the Algarve region and the prolific decoration techniques and numerous different materials used in its production. This work was supported by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT-Portuguese Foundation for Science and Technology under the following project references: UIDB/50025/2020-2023 (CENIMAT), UIDB/00729/2020 (VICARTE), UIDB/04449/2020 (HERCULES) and, 2021.04858.BD (Ana S. Saraiva). References Ferreira, L.F. Vieira, R. Varela Gomes, M.F.C. Pereira, L.F. Santos, and I. Ferreira Machado. 2016. ?Islamic Ceramics in Portugal Found at Silves Castle (8th to 13th c.): An Archaeometric Characterization?. Journal of Archaeological Science: Reports 8 (August): 434?43. https://doi.org/10.1016/j.jasrep.2016.06.051. Gomes, Rosa Varela. 2002. Silves (Xelb), uma cidade do Gharb al-Andalus: território e cultura (Trabalhos de Arqueologia, 23). Lisboa: IPA (in Portuguese); Gomes, Rosa Varela. 2004. (Xelb), uma cidade do Gharb al-Andalus: a Alcáçova (Trabalhos de Arqueologia, 35). Lisboa: IPA (in Portuguese); Gomes, Rosa Varela. 2006. Silves (Xelb), uma cidade do Gharb al-Andalus: o núcleo urbano (Trabalhos de Arqueologia, 44). Lisboa: IPA (in Portuguese); Gomes, Rosa Varela. 2011. Silves (Xelb), uma cidade do Gharb al-Andalus: a zona da Arrochela (Trabalhos de Arqueologia, 53). Lisboa: IGESPAR (in Portuguese). Torres, Cláudio, and Santiago Macías. 1992. ?O Garb-Al-Andaluz?. In História de Portugal, I:360?437. Lisboa: Círculo de Leitores (in Portuguese).