A low-cost automatic acquisition system for photogrammetry

Photogrammetry is a non-destructive technique commonly employed in the cultural heritage field for reconstructing a 3D virtual replica of an artifact by simply taking several photos of the artifact itself from different points of view. The 3D model can be used either for documenting the artifact or for preserving its geometrical information and appearance. Moreover, by using a digital 3D model is extremely easy sharing information with the public and researchers without physically moving the artifact, and this represents a unique opportunity which cannot be achieved with traditional methods. Unfortunately most systems already present on the market are complex and costly both due to their hardware and software. This paper presents a novel acquisition system which is extremely cheap and can be easily arranged in any conservation laboratory. The solution is based on a simple acquisition system designed with the aim of providing researchers with a user-friendly and low-cost platform for the reconstruction of an artifact 3D model. The proposed system can be virtually interfaced to every commercial camera and can be integrated with several 3D reconstruction software. As an example, the authors employed a free open-source software referred to as Meshroom

Application of μ-Raman spectroscopy to the study of the corrosion products of archaeological coins

In this paper, a study of the corrosion products formed on archaeological bronze artefacts excavated in Tharros (Sardinia, Italy) is presented. The investigation was carried out by means of the combination of different analytical techniques, including optical microscopy, micro-Raman spectroscopy (µ-RS), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy and X-ray diffraction. The artefacts under study are three bronze coins from the Phoenician-Punic period that are deeply corroded due to the chloride-rich soil of the Tharros excavation site. µ-Raman spectroscopy was chosen to investigate the corroded surfaces of the artefacts because it is a non-destructive technique, it has high spatial resolution, and it makes it possible to discriminate between polymorphs and correlate colour and chemical composition. Through µ-RS, it was possible to identify different mineralogical phases and different polymorphs, such as cuprite (Cu2O), copper trihydroxychloride [Cu2Cl(OH)3] polymorphs, hydroxy lead chloride laurionite [PbCl(OH)] and calcium carbonate polymorph aragonite. The experimental findings highlight that micro-Raman spectroscopy can be used to provide further knowledge regarding the environmental factors that may cause the degradation of archaeological bronzes in soil

Micro-Raman investigation of dangerous corrosion products of archaeological bronzes from Tharros (Sardinia-Italy)

A large number of bronze artefacts have been found during archaeological excavations carried out at Tharros (Sardinia, Italy). The composition of corrosion products have been determined by the combined use of optical microscopy (OM), micro-Raman spectroscopy (μ-Raman), scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS). In particular, we will use μ-Raman spectroscopy to identify the corrosion products of natural patinas. This technique is equivalent or sometimes more efficient than microscopic and diffraction techniques to identify archaeological corrosion products. It is able to discriminate between different polymorphs, has a high spatial resolution and assures a correlation between the colour and the mineralogical nature. Furthermore has the advantage of being a nondestructive technique, quality highly valued in the cultural heritage

Atmospheric corrosion of outdoor bronze artefacts: The case study of 'Katarsis', by Magdalena Abakanowicz

The conservation of cultural heritage metallic items is deeply connected to the investigation of the corrosion phenomena affecting the metallic surface and to the study of the influence of the surrounding environmental parameters. This paper describes the case study regarding the metallic artwork 'Katarsis' of the Gori Art Collection at Fattoria di Celle (Pistoia, Italy), created by the artist Magdalena Abakanowicz. An in-situ multi-analytical approach was employed in order to assess the conservation state of the statues and to ensure their long-lasting preservation. In particular, X-rays fluorescence (XRF), Raman spectroscopy (RS), and X-Rays diffraction (XRD) were used for the identification of the corrosion products, mainly sulphates, and to identify the employed alloy. In this paper, the preliminary results will be presented and discussed

Raman investigation of corrosion products on Roman copper-based artefacts

This paper illustrates a case study related to the characterisation of corrosion products present on recently excavated artefacts. The archaeological findings, from the Rakafot 54 site (Beer-Sheva, Israel), consist of 23 coins and a pendant, all dating back to the Roman period. Raman spectroscopy was used to identify the corrosion products that compose the patina covering the objects. To facilitate and support their identification, spectra were then processed using principal components analysis. This chemometric technique allowed the identification of two main compounds, classified as atacamite and clinoatacamite, which formed the main components of the patinas. The results of this investigation can help in assessing the conservation state of artefacts and defining the correct restoration strategy

Non-invasive characterization of ancient Cu-based coins using Raman spectroscopy

Characterization of archaeological finds is a challenging case study for researchers, as the need of non-invasive measurements strongly affects the investigation strategies. Moreover, it is almost not possible to follow a fixed protocol, because the measurement conditions should be tailored to the samples under study. This paper presents a preliminary characterization of bronze coins coming from an archaeological site located in the south of Israel. The superficial corrosion layers have been analysed by means of Raman spectroscopy in order to investigate their composition and assess the conservation state of the finds. Reference samples of known composition have also been used to help peaks identification in the Raman spectra. Results coming from this study can help in defining the correct conservation strategies for the artefacts

In-situ multi-analytical study of ongoing corrosion processes on bronze artworks exposed outdoors

This paper presents a long-term in-situ campaign to monitor contemporary bronze statuary exposed outdoors. The case study relates to the characterisation of three sculptures belonging to the Gori Art Collection, located in the Fattoria di Celle: 'Cavaliere' and 'Miracolo - Composizione' by Marino Marini and 'Due forme o due ombre n°2' by Luciano Minguzzi. The overall conservation state of the sculptures was investigated by means of a multi-analytical and non-invasive approach, involving different techniques. Three-dimensional photogrammetry was performed to fully document the artworks. The chemical and microstructural features of the corrosion patinas were then characterised through X-ray fluorescence and Raman spectroscopy. In addition, the stability and the protective effectiveness of the corrosion products were assessed by electrochemical impedance spectroscopy. Thanks to the combined use of these specific techniques, the information extracted through the different analyses could be correlated with each other and with the exposure conditions. The different corrosion products were identified as being primarily copper sulphates and phosphates, and they were correlated with the different microclimate conditions related to their location on the statues. The information gathered from the presented multi-analytical approach represents the fundamental knowledge required to develop a tailored conservation project to assure the long-lasting preservation of these artworks

Monitoraggio dello stato di conservazione delle opere d’arte della Collezione Gori

Il monitoraggio dello stato di conservazione dei manufatti metallici è di grande rilevanza nel mondo dei beni culturali ed è essenziale per lo sviluppo di metodologie e buone pratiche per la conservazione preventiva di manufatti metallici d’interesse storico-artistico esposti all’aperto. In questo lavoro è presentato il monitoraggio di una scultura in bron- zo appartenente alla Collezione d’arte Gori, raccolta privata di un grande numero di opere d’arte moderna, realizzate all’interno di un programma di arte ambientale. In particolare è stato eseguito uno studio tramite l’impiego di tecniche non invasive, applicabili in situ, che permettessero di attestare la presenza dei fenomeni corrosivi in atto e la caratteriz- zazione delle patine di corrosione presenti. Le tecniche impiegate sono la spettroscopia di impedenza elettrochimica (EIS), la spettroscopia Raman e la fotogrammetria. Mediante lo sviluppo di un approccio d’indagine multi-analitico è stato possibile valutare nel complesso lo stato di conservazione dell’opera e la capacità protettiva delle patine

Raman and micromorphological characterization of carbonates in plaster-like materials from the Natufian site of Eynan (Ain Mallaha), Israel

The archaeological site of Eynan, located by the spring of Ain Mallaha and on the shores of Lake Hula in the Upper Jordan Valley, Israel, existed for several millennia at the end of the Pleistocene. During the Natufian culture of the Levantine Epipalaeolithic, the site was one of the largest known occupations in the Levant for some millennia (ca. 14,300 - 11,900 cal BP). Remains of Natufian architecture were found, together with evidence of early experimenting with pyrotechnology for the creation of lime plaster. Several features were identified during the excavations as assumed lime plaster installations. Samples investigated by micromorphology methods under the polarizing microscope revealed that while all were composed of calcium carbonate, and some indeed represent anthropogenic burnt lime products, others reflected the results of post-depositional or contemporaneous natural processes rather than technological products. The study of the samples at a molecular level through Raman spectroscopy enables a new methodology for the quick distinction between the features observed by micromorphology