A non-invasive study of the effect of three commercial cleaning products on shellac-coated mahogany

The Royal Palace of Norway has a large 19th century wooden furniture collection and most of it is coated with shellac-based varnishes. Since these objects are part of the royal collections, they are still in daily use at the different residences and, therefore, need to be frequently cleaned. In this work, the effect of three cleaning commercial products (Baolin, Centurio, Fulgentin) used at the royal collections on shellac-coated mahogany is investigated for the first time. A non-invasive methodology (portable ER-FTIR spectroscopy and colorimetry) was applied to assess whether the chemical composition and the color of fresh and artificially aged mahogany wood mock-ups coated with shellac were affected by the above-mentioned cleaning products. This study shows that one of them causes changes in the varnished wood, thus potentially affecting the long-term conservation of this furniture collection.This work has been supported by grant TED2021-129299A-I00, funded by MCIN/AEI/10.13039/501100011033 and by the European Union NextGenerationEU/PRTR

Use of portable devices and confocal Raman spectrometers at different wavelength to obtain the spectral information of the main organic components in tomatoes (Solanum Lycopersicum) fruits

Tomato (Solanum lycopersicum) fruit samples, in two ripening stages, ripe (red) and unripe (green), collected from a cultivar in the North of Spain (Barrika, Basque Country), were analyzed directly, without any sample pretreatment, with two different Raman instruments (portable spectrometer coupled to a micro-videocamera and a confocal Raman microscope), using two different laser excitation wavelengths (514 and 785 nm, only for the confocal microscope). The combined use of these laser excitation wavelengths allows obtaining, in a short period of time, the maximum spectral information about the main organic compounds present in this fruit. The major identified components of unripe tomatoes were cutin and cuticular waxes. On the other hand, the main components on ripe tomatoes were carotenes, polyphenoles and polysaccharides. Among the carotenes, it was possible to distinguish the presence of lycopene from b-carotene with the help of both excitation wavelengths, but specially using the 514 nm one, which revealed specific overtones and combination tones of this type of carotene.This work has been financially supported by Research Project S-PE11-UN128 of the Basque Country government. Technical and support provided by SGIker (UPV/EHU, MICINN, GV/EJ, ESF) is gratefully acknowledged

A study of the artistic corpus of red cave paintings in El Buxu cave (Cangas de Onís, Asturias, Spain)

El Buxu cave, which is located in the village of Cardes (Cangas de Onís, Asturias), has been studied since the 1980s, with multiple excavations taking place inside the cave. This work has uncovered a complete artistic corpus, marking out several phases of occupation, with paintings dating to the first phases of the Upper Palaeolithic, Solutrean and Lower and Middle Magdalenian periods. This paper presents a new review of its rock art, documenting all of the red paintings inside the cave, most of which have never been published up until this point. The most notable inclusion is the new description of a zoomorphic figure painted in red, which has previously been interpreted as an aurochs, but whose features are in fact closer to those of a deer or reindeer. In addition, stratigraphic analysis of some of the paintings has revealed that they are overlapped by Solutrean and Magdalenian engravings and black paintings inside the cave. Elemental analysis was performed on series of red pigments and ochre samples, recovered from various strata using X-ray fluorescence spectroscopy. The resulting dataset was treated using Principal Component Analysis, providing a deeper understanding of the composition of the rock art in El Buxu cave, while uncovering potential correlations between the samples ac- cording to their elemental composition. After comparing additional evidences from other red cave paintings in the region with the red pictographs in the cave, along with the stratification of paint pigments and their relationship with the ochre samples in each stratum, it appears that the red paintings comprise the oldest group of pictures inside the cave and can be broadly dated to the pre-Magdalenian cultural period.Our special aknowledgment to the National University of Distance Education (UNED), for its funding for open-access publishin

Nature and origin of white efflorescence on bricks, artificial stones, and joint mortars of modern houses evaluated by portable Raman spectroscopy and laboratory analyses

Bricks and mortar currently constitute one of the most important building materials used in the construction of most modern facades. The deterioration of these materials is caused primarily by the impact of numerous external stressors, while poor manufacturing quality, particularly of mortars, can also contribute to this process. In this work, the non-invasive Raman spectroscopy technique was used to identify the recently formed deterioration compounds (primarily sulfates and nitrates) in bricks, artificial stones, and joint mortars from detached houses in the Bilbao metropolitan area (Basque Country, North of Spain), as well as to investigate the deterioration processes taking place in these materials. Additionally, to confirm and in some cases complement the results obtained with Raman spectroscopy, SEM-EDS and XRD measurements were also carried out.This work was financially supported by DEMBUMIES (ref.BIA2011-28148) and funded by the Spanish Ministry of Economy and Competitiveness (MINECO). H. Morillas is grateful to the University of the Basque Country (UPV-EHU) and particularly to the UFI 11-26 Global Change and Heritage, who funded his pre-doctoral fellowship. Technical support provided by the Raman-LASPEA and General X-ray Service: Rocks and Minerals laboratories of SGIker (UPV/EHU, MICINN, GV/EJ, ERDF and ESF) is also gratefully acknowledged

Secco painting technique revealed in non-restored Pompeian murals by analytical and imaging techniques

The fresco technique appears to have been widely used on Roman mural paintings. The close observation of many of such murals suggests, however, the application of a secco technique over the fresco background. In this work, for the first time, fragments from Pompeian mural paintings that had never been restored have been investigated by optical microscopy, reflectance transformation imaging, micro-Energy-Dispersive X-Ray Fluorescence, micro-Fourier Transform Infrared Spectroscopy, and Direct Temperature-resolved Mass Spectrometry. A small number of fragments from restored paintings from the same Archaeological Park was also analyzed by the same techniques for the sake of comparison. The results of this multi-analytical approach that involves - for the first time on this type of samples - scientific photographic investigation, point out to the use of a protein- based medium, most probably egg, to execute the secco layers. On the other hand, wax was ubiquitous in samples taken from restored mural paintings. This last evidence further highlights the importance of selecting appropriate candidates for the study of original organic binders.Silvia Pérez-Diez: “la Caixa” Foundation-Fellowship code LCF/BQ/ES18/11670017 Francesco Caruso: Maria Zambrano fellowship from the University of the Basque Country (UPV/ EHU), funded by the Spanish Ministry of Universities and the European Union NextGenerationEU/PRTR. Project DEMESOS (PES21/85), UPV/EH

Unraveling the role of the thermal and laser impacts on the blackening of cinnabar in the mural paintings of Pompeii

The blackening of red cinnabar (α-HgS) pigment has traditionally been explained by its conversion into black metacinnabar (β-HgS). Scarce is however the scientific evidence that supports this hypothesis in polychrome artworks. As such transition occurs at around 345 °C, the thermal impact of the eruption of Mount Vesuvius in 79 AD could have induced this structural change of the pigment present in the mural paintings of Pompeii. This work aims to assess whether the mentioned volcanic eruption could be responsible of the cinnabar blackening through the formation of metacinnabar. The thermodiffractometry study of cinnabar-decorated fresco mock-ups stated that the formed β-HgS is not stable, observing its reversion into α-HgS. Moreover, sublimation of the cinnabar pictorial layer was registered, also when the cinnabar paint layer was protected by a coating of pyroclastic materials. In real blackened cinnabar Pompeian samples, it was not possible to identify metacinnabar by X-ray diffraction (XRD), but evidence of sublimation of mercury due to the thermal impact was observed. Hence, this blackening seems to be related mainly to the presence of calomel (Hg2Cl2) and a gypsum (CaSO4·2H2O) crust as degradation products of red cinnabar and the calcite mortar, respectively, and not to the formation of metacinnabar. Finally, laser-based techniques could also induce modifications in the HgS crystalline structure, resulting in an amorphous black product. Therefore, the elemental and molecular study of the species promoted by laser impact was carried out to avoid false positives in the metacinnabar detection or when the decorated surface has been subjected to laser cleaning.The research leading to these results has received funding from “la Caixa” Foundation (Silvia Pérez-Diez, ID 100010434, Fellowship code LCF/BQ/ES18/11670017). This work has been supported by the project IT1446-22 for Consolidated Research Groups, funded by the Basque Country Government. The authors acknowledge as well the funding provided by University of the Basque Country through the Institutionally Sponsored Open Access

Evaluation of black crust formation and soiling process on historical buildings from the Bilbao metropolitan area (north of Spain) using SEM-EDS and Raman microscopy

In the present work, several building materials suffering from black crusts and soiled surfaces were evaluated by scanning electron microscopy energy dispersive X-ray spectrometry (SEM-EDS) and micro-Raman spectroscopy. The goal was to examine the elemental and molecular composition, the distribution on the samples, and the morphology of endogenous and exogenous compounds on those black crusts and soiled surfaces. The black crusts were deposited over different building materials such as limestone, sandstone, and brick that constitute a small construction called "malacate" as well as over a limestone substrate of a cemetery gate. Both constructions are dated back to the beginning of the twentieth century. The samples of soiling were taken from the façade of a building constructed in the 1980s. The analytical evaluation allowed in a first stage the determination of the composition and the observation of the morphology of soiling and black crusts. In addition, the evaluation of the compositions of the soiling and black crusts of different grade and formation allowed the assessment of the main weathering phenomena that the buildings have suffered, which were found to be sulfate impact, marine aerosol impact, depositions of metallic particles, crustal particulate matter depositions, carbonaceous particles, biodeterioration, and vandalism.This work has been funded by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project DISILICA-1930 (ref. BIA2014-59124-P) and the Regional Development Fund (FEDER). E. Calparsoro is grateful also to the Spanish Ministry of Economy and Competitiveness (MINECO) who funded his pre-doctoral fellowship (ref. BES-2014-068940)

Portable and Raman imaging usefulness to detect decaying on mortars from Punta Begoña Galleries (Getxo, North of Spain)

Punta Begoña Galleries were built in 1918 in Getxo (Basque Country, North of Spain) but were abandoned in 1960. Nowadays, their conservation state is very poor. In this work, portable Raman spectroscopy was applied to evaluate the original composition and possible deterioration products of the mortars used in the inner walls and those covering the concrete of the ceilings allowing us to select the most appropriate sampling points. In the laboratory, Raman microscopy and Raman imaging, assisted with scanning electron microscopy equipped with an energy dispersive spectrometer (SEM‐EDS), X‐ray diffraction and energy dispersive X‐ray fluorescence (ED‐XRF) imaging, allowed to identify the key compounds to understand the deterioration processes taking place in the mortars of the galleries. The main components of the mortars from the walls were calcite and gypsum. In some cases, alite (Ca3SiO5) and belite (Ca2SiO4) were identified; these components are characteristic of Portland cement clinker. The main components of the mortar covering the concrete were calcite, quartz, aragonite and gypsum. The aragonite identification confirmed the use of beach sand as the aggregate in the mortar. The concrete from the ceiling of the lower gallery is covered with three different mortar layers; the outermost layer is covered with a black crust. In the three mortars, the main components are similar to those used in the mortar covering the concrete from the upper gallery. Thanks to Raman, ED‐XRF and SEM‐EDS imaging, it was possible to map the distribution of the main components through the three mortar layers and also to identify the presence of dolomite {[CaMg(CO3)2]}, which was not possible to detect following single‐point micro‐Raman analyses.This work has been funded by the Ministry of Economy and Competitiveness and the European Regional Development Fund (ERDF) through the project DISILICA‐1930 (ref. BIA2014‐59124‐P) and by the cooperation agreement between the University of the Basque Country (UPV/EHU) and the City Council of Getxo (OTRI2014‐0639). C. García‐Florentino is grateful to the University of the Basque Country (UPV/EHU), which funded her predoctoral fellowship. Technical support provided by Raman‐LASPEA Laboratory and General X‐ray Service of the SGIKer (UPV/EHU, Ministry of Economy and Competitiveness of Spain, Basque Government, ERDF and European Social Fund) is also gratefully acknowledged

Multianalytical Approach to explain the darkening process of hematite pigment in paintings from ancient Pompeii after accelerated weathering experiments

[EN] In this paper, recently excavated fresco painting fragments from the House of Marcus Lucretius (Pompeii) and not exposed to the atmosphere since the eruption of the Mount Vesuvius were subjected to a controlled SO2 atmosphere and high relative humidity. These experiments were conducted in order to simulate under accelerated conditions the possible deterioration of the hematite pigment and plaster. The mineralogical transformation of the polychromy and plaster was monitored using mainly Raman spectroscopy, a non-destructive technique, but also infrared spectroscopy (FT-IR) and scanning electron microscopy energy-dispersive X-ray spectroscopy (SEM-EDS). After different exposure cycles to SO2, it was confirmed that hematite red pigment (Fe2O3) can be reduced into magnetite (Fe3O4), which provides the darkened colour to the pigment. While Fe(III) from hematite is reduced into Fe(II) or mixed Fe(III) and Fe(II), the SO2 can be oxidized (SO3) and hydrated to experience a subsequent wet deposition (H2SO4 aerosol) causing also the transformation of calcite into gypsum. Finally, it was assessed that high concentrations of SO2 can also cause the sulphation of hematite pigment promoting its transformation into paracoquimbite/coquimbite (Fe2(SO4)3$9H2O). Moreover, in some areas of the deteriorated painting fragments, non-expected iron(II) sulphate and sulphite species were also identified

Elemental imaging approach to assess the ability of subaerial biofilms growing on constructions located in tropical climates as potential biomonitors of atmospheric heavy metals pollution

Over the last decades, the concern about air pollution has increased significantly, especially in urban areas. Active sampling of air pollutants requires specific instrumentation not always available in all the laboratories. Passive sampling has a lower cost than active alternatives but still requires efforts to cover extensive areas. The use of biological systems as passive samplers might be a solution that provides information about air pollution to assist decision-makers in environmental health and urban planning. This study aims to employ subaerial biofilms (SABs) growing naturally on façades of historical and recent constructions as natural passive biomonitors of atmospheric heavy metals pollution. Concretely, SABs spontaneously growing on constructions located in a tropical climate, like the one of the city of Barranquilla (Colombia), have been used to develop the methodological approach here presented as an alternative to SABS grown under laboratory conditions. After a proper identification of the biocolonizers in the SAB through taxonomic and morphological observations, the study of the particulate matter accumulated on the SABs of five constructions was conducted under a multi-analytical approach based mainly on elemental imaging studies by micro Energy Dispersive X-ray fluorescence spectrometry (μ-EDXRF) and Scanning Electron Microscopy coupled with Energy Dispersive X-ray spectrometry (SEM-EDS) techniques, trying to reduce the time needed and associated costs. This methodology allowed to discriminate metals that are part of the original structure of the SABs, from those coming from the anthropogenic emissions. The whole methodology applied assisted the identification of the main metallic particles that could be associated with nearby anthropogenic sources of emission such as Zn, Fe, Mn, Ni and Ti by SEM-EDS and by μ-EDXRF Ba, Sb, Sn, Cl and Br apart others; revealing that it could be used as a good alternative for a rapid screening of the atmospheric heavy metals pollution.This work has been supported by the project IT1446-22 for Research Groups of the Basque University System, funded by the Basque Country Government. Open Access funding provided by University of the Basque Country is also gratefully acknowledged. The authors thank for technical and human support provided by SGIker (UPV/EHU/ERDF, EU) and concretely to Alfredo Sarmiento from Coupled Multispectroscopy Singular Laboratory (Raman-LASPEA)