Cultural Heritage Diagnostics Research Articles

Unusual Composition of the Sarezzano Reliquary Busts

The interdisciplinary study of two reliquary busts from Sarezzano (Piedmont, Italy) is a perfect example of the necessity to provide for material characterisation as a recurring common practice in historical studies and a mandatory step in conservation assessment. Furthermore, the diagnostics of cultural heritage play a crucial role in art historical research, providing relevant information on artefacts’ genesis, production technology, and conservation history. The study of the materials of the reliquary busts was performed by non-invasive (portable X-ray fluorescence spectrometry) and micro-invasive (stereomicroscope, attenuated total reflection Fourier transform infrared spectroscopy and powder X-ray diffraction analysis) methods. According to the results, the busts were found to be made of a tin–lead alloy, a rather unusual material for mediaeval reliquary busts. Moreover, the outcome suggests that the busts were originally silvered, except for the hair and beard which are still gilded. The analysis reveals the use of colophony as an adhesive buffer layer on the busts’ alloy, as well as inside them, to favour the metal working process, since it is found as degraded residue. Finally, even the typology of alloy decay is defined. All this information has enabled us to determine the artistic technique and estimate the value and quality of the material employed. In addition, it has led to the correct choice of materials and methods to be adopted during the restoration, and therefore the usage of more suitable solvents and tools.

Seismic Vulnerability Assessment of Historic Centers with Two Fast Methods Based on CARTIS Survey Methodology and Fragility Curves

After an earthquake, legislation tends to permit the rapid demolition of damaged buildings, including the built heritage, for safety reasons, as was the case for many small historic centers after the 2016 earthquake in central Italy. A balance should, of course, be struck between safety and preservation. There must be a willingness to engage in continuous interaction with the various bodies involved in post-earthquake management, particularly in the preventive phase of the complex activities regarding the issues of the seismic vulnerability of historic built. The widespread historical built heritage in Italy requires fast and reliable assessment procedures that allow a large-scale evaluation of the vulnerability of historical buildings before a seismic event. To this end, a proposal is presented here for the inverse use of the protocol for the seismic vulnerability survey of historic centers by means of a system called CARTIS form, coordinated since 2015 by the Italian consortium of Seismic and Structural Engineering Laboratories (ReLUIS). This rapid assessment is compared with an equally fast method for constructing fragility curves, based only on the information available in the ReLUIS–CARTIS database, defining the relationship between the probability of reaching a level of loss of structural safety or a vulnerability index as a function of the seismic acceleration PGA and the ground orography. The methodology outlined could be considered to be progress in cultural heritage diagnostics on a large scale, considering cultural heritage to be the diffuse historical residential masonry buildings that form the historic centers.

Calibration-free 3D ray-tracing beam hardening correction in computed tomography

In this paper we introduce a calibration-free beam-hardening correction technique in computed tomography, which improves the results achieved by a state-of-the-art correction method. Two main practical points are here underlined: (1) the need to perform a beam hardening correction without previous calibration; (2) the need to consider the shape of the object in all its whole three-dimensional extent. The proposed method requires: (a) a first complete reconstruction of the object by means of a cone-beam filtered back projection algorithm; (b) a segmentation of the reconstructed volume; (c) the construction of the attenuation when varying path-length graph; (d) the interpolation of the experimental data on the graph with a convenient mathematical function; (e) the correction of the measured attenuation values; (f) to perform again the complete cone-beam reconstruction. The result is an effective beam-hardening calibration-free correction over a large variety of objects, easy to use and quite fast. The proposed method results particularly useful when both the measurement time and the control of the geometry of the system are limited, like the ones generally faced in Cultural Heritage diagnostics. Computed Tomography reconstructions for test samples and for real cases are provided to highlight the effectiveness and the advantages of the new suggested approach.

Stratigraphy of Fresco Paintings: A New Approach with Photoacoustic and SORS Imaging.

Photoacoustic (PA) imaging is a novel, powerful diagnostic technique utilized in different research fields. In particular, during recent years it has found several applications in Cultural Heritage (CH) diagnostics. PA imaging can be realized in transmittance or epi-illumination (reflectance) modes, obtaining variable levels of contrast and spatial resolution. In this work, we confirmed the applicability of the PA technique as a powerful tool for the imaging of one of the most challenging artwork objects, namely fresco wall paints, to obtain precise stratigraphic profiles in different layered fresco samples. In this regard, we studied some multi-layered fragments of the vault of San Giuseppe Church in Cagliari (1870 AD) and some mock-ups realized specifically to test the potentiality of this technique. Due to complex structures of the frescoes, we used the Spatially Off-set Raman Spectroscopy (SORS) technique to provide complementary information. The experimental results were in agreement for both techniques, even for the three-layered complex structure, and were confirmed with Scanning Electron Microscopy (SEM) analysis of cross-sections. The combined use of these two techniques proved useful to investigate detailed hidden information on the fresco samples.

SERS using nanostar‐in‐cavity structures

AbstractParticle in cavity nanostructures were produced by sedimentation of silver nanostars (AgNSs) onto sphere segment void (SSV) cavity structures produced by electrodeposition of gold around templates formed by assembling close packed monolayer arrays of 220 or 600 nm diameter polystyrene spheres. The resulting AgNS@SSV nanostructures were characterized by scanning electron microscopy and their performance as substrates for surface enhanced Raman spectroscopy (SERS) was examined. The enhancement factors obtained for the different structures were evaluated using benzenethiol as Raman probe, which adsorbs on Ag and Au to form a monolayer with uniform coverage, so allowing the enhancement to be quantified. Higher enhancements were obtained for the AgNSs@SSV substrates as compared with the gold SSV structures. The greatest enhancements were obtained when matching cavity and nanostar dimension so that only one nanostar could be accommodated in the cavity. The AgNS@SSV substrates were then shown to be promising substrates for the highly sensitive detection of dyes and, particularly, for the lake‐pigment cochineal lake, providing useful information and novel analytical tool for application in the field of cultural heritage diagnostics and conservation.

Microgeophysics and geomatics data integration reveals the internal fracturing conditions of the statue of Ramses II (Museo Egizio, Torino, Italy)

The combined acquisition of 3D ultrasonic tomography and radar scans is growing for cultural heritage diagnostics. Both methods proved to be efficient in the detection and location of fractures and weaknesses within the investigated artefacts. Although the two techniques are widely applied together, an integrated approach for data interpretation is still missing. We present the results of radar and ultrasonic prospections carried out on the statue of the young Ramses II, an absolute masterpiece of the Egyptian art preserved in the collection of the Museo Egizio of Torino (Italy). Geophysical results are incorporated within the 3D model of the statue retrieved from total station measurements, ground-based and handheld laser scanning. A data integration approach is then proposed for the joint interpretation of the geophysical results, exploiting the final ultrasonic velocity model and radar attribute analysis (i.e. local dissimilarity computation) to define a combined damage index. The proposed methodology is efficient in fracture detection and location and improves the readability of the final results also for non-expert geophysical interpreters, offering guidance to the museum for preservation and restoration of the masterpiece.

VAULTED STRUCTURES IN THE ARCHAEOLOGICAL PARK OF POMPEII: 3D SURVEY AND MONITORING

Abstract. The contribution focuses on the relationship between preventive conservation and digital technologies, with particular attention to the Archaeological Park of Pompeii and its masonry vaults. These fragile macro-elements, both for their intrinsic condition of ruins and for their historical vulnerability to seismic stress, were detected through a careful 3D survey, in the context of the Great Pompeii Project (GPP). The analysis was carried out in 2015 with laser-scanning technology and photogrammetry, and was aimed at the knowledge, documentation and measurement of conditions of degradation or instability. On the basis of a deep knowledge, supported by in situ investigations, it was possible to define the most appropriate conservative interventions for vaulted structures. Also, the interpretation of the vulnerabilities and of the causes of degradations phenomena allowed focusing on the program phase, in order to maintain the benefits of restoration over time. Moreover, the contribution anticipates how these surveys will be integrated by a doctoral research with industrial characterization. This research is currently being conducted in close relationship with Tecno In – a leading company in the field of knowledge and diagnostics of cultural heritage – and its object is the experimentation of innovative techniques for diagnostics, preventive conservation and restoration of the vaulted structures of Pompeii. Therefore, in the comparison with the surveys realized in 2015 lies the opportunity of deepening the understanding and of monitoring the evolution of degradation conditions of the vaulted buildings under exam.

Interpolation methods in GPR tomographic imaging of linear and volume anomalies for cultural heritage diagnostics

This paper presents results of a ground penetrating radar (GPR) survey conducted in St. Joseph’s Church in Gdańsk, Poland. The aim of the study was to produce tomographic imaging of a renovated floor as well as the objects buried under the floor to detect linear and volume inclusions. The assumed track spacing was meaningfully greater than the single signal spacing in each track, which induced the need for interpolation methods to estimate signal values in the areas beyond the trace lines. Various interpolation techniques were used to prepare the tomography maps. GPR time slices allowed the identification of reinforcing meshes, underfloor heating system elements and the foundations of entrances to crypts. The results obtained were compared to the exact images acquired in a dense regular grid to evaluate the efficiency of the applied interpolation methods and to verify the possibility of conducting GPR surveys with coarse track spacing.

In situ and remote laser diagnostics for material characterization from plasma facing components to Cultural Heritage surfaces

Optical and spectroscopic techniques offer unique possibilities for non destructive or micro-destructive characterization of surfaces, with widespread applications, starting from in-line monitoring of industrial processes. A significant group of industrial applications concerns nuclear grade material characterization and plasma diagnostics relevant to the thermonuclear fusion process. However, technologies and methodologies originally developed for specific in-vessel utilization, can easily find additional in-situ and remote application to environmental and cultural heritage (CH) diagnostics addressed to preventive conservation and restoration of surfaces. At ENEA Frascati different prototypes have been developed and patented to collect reflectance and fluorescence images excited at different ultraviolet and visible laser wavelengths, Raman and LIBS signals. Portable integrated instruments suitable for operation at different distances from a 1.5 to 30 m, have been assembled and operated in laboratory on multilayered samples and in field campaigns for Security and on CH painted surfaces. Significant results relevant to the cross fertilization among different applications will be presented and discussed.

Hypercolorimetric multispectral imaging system for cultural heritage diagnostics: an innovative study for copper painting examination

The aim of this work is to test the application of a new multispectral imaging system, named Hypercolorimetric Multispectral Imaging, on two little 17th century oil paintings on copper in order to support the restoration activities. Hypercolorimetric Multispectral Imaging is a non-invasive, rapid and diagnostic technique that allows in situ accurate and reproducible spectral reflectance measurements between 300nm and 1000nm to obtain seven monochromatic very high spatial resolution images (36 megapixels starting from RAW format). The acquired images are transformed into radiometric and colorimetric measurements, consisting of 7 monochromatic images of spectral reflectance and one colorimetric image. All these calibrated images constitute the base for further processing performed through a dedicated software that implements a number of functions. In the present paper, a subset of those functions has been used. Specifically: Principal Component Analysis, spectral clustering, spectral mapping, multiband contrast enhancement and edge detection. Combining calibrated images of different spectral regions acquisitions, it was possible to extract relevant information about the state of conservation of the two copper paintings and further significant details were readable compared with the data coming from each single acquisition. The Hypercolorimetric Multispectral Imaging acquisition process revealed to be fast allowing to be performed during the cleaning stage of the paintings. The imaging nature of the analysis allowed to compare and map different areas of the surfaces producing degradation maps of the painting layers, which represents a precious decision-making tool for conservators.

Spectroscopy for contemporary art: Discovering the effect of synthetic organic pigments on UVB degradation of acrylic binder

The influence of Synthetic Organic Pigments in the degradation of Acrylem AC 33, a waterborne acrylic binder, after UVB-artificial exposure was furtherly investigated, extending the study to other pigments classes (anthraquinones, phthalocyanines, diketo-pyrrolo-pyrroles) in addition to previously studied azo-pigments. Together with Fourier Transform Infrared, both in Attenuated Reflectance and Transmission mode, and Nuclear Magnetic Resonance spectroscopies, Raman spectroscopy was also used to observe ageing processes that pigments are subjected to. Specific effects, relative to the presence of different pigments, have been observed also in this study; moreover, Raman spectroscopy highlighted photoinduced effects on some pigments, which could result useful in Cultural Heritage diagnostics, especially for street artworks.

Dielectric permittivity diagnostics as a tool for cultural heritage preservation: Application on degradable globigerina limestone

Most monuments and historical buildings in the Maltese Islands are made of the local Globigerina Limestone (GL). This type of stone, however, is very delicate and prone to degradation caused by the environmental conditions of the islands. Hence, for the preservation of the Cultural Heritage monuments, it is necessary to promptly assess the health status of these structures and, in particular, their water content (which represents one of the major causes of degradation).Starting from these considerations, in this work, a time domain reflectometry (TDR)-based method for estimating water content of GL is presented. More specifically, the proposed method relies on estimating the water content value of the GL structure from TDR-based dielectric permittivity measurements. To verify the suitability of this system, experimental tests were carried out on a GL sample. In addition to this, also the dielectric characterization of GL was carried out. The results anticipate the strong potential of the proposed method for practical applications in the Cultural Heritage diagnostics.

Physics meets fine arts: a project-based learning path on infrared imaging

Infrared imaging represents a noninvasive tool for cultural heritage diagnostics, based on the capability of IR radiation to penetrate the most external layers of different objects (as for example paintings), revealing hidden features of artworks. From an educational viewpoint, this diagnostic technique offers teachers the opportunity to address manifold topics pertaining to the physics and technology of electromagnetic radiation, with particular emphasis on the nature of color and its physical correlates. Moreover, the topic provides interesting interdisciplinary bridges towards the human sciences. In this framework, we present a hands-on learning sequence, suitable for both high school students and university freshmen, inspired by the project-based learning (PBL) paradigm, designed and implemented in the context of an Italian national project aimed at offering students the opportunity to participate in educational activities within a real working context. In a preliminary test we involved a group of 23 high school students while they were working as apprentices in the Laboratory of Applied Physics for Cultural Heritage (ArcheoLab) at the University of Calabria. Consistently with the PBL paradigm, students were given well-defined practical goals to be achieved. As final goals they were asked (i) to construct and to test a low cost device (based on a disused commercial camera) appropriate for performing educational-grade IR investigations on paintings, and (ii) to prepare a device working as a simple spectrometer (recycling the optical components of a disused video projector), suitable for characterizing various light sources in order to identify the most appropriate for infrared imaging. The proposed learning path has shown (in the preliminary test) to be effective in fostering students’ interest towards physics and its technological applications, especially because pupils perceived the context (i.e. physics applied to the protection and restoration of cultural heritage) as relevant in relation to the cultural and productive specificities of their country. The learning sequence, originally designed for high school students in apprenticeship at the university, can be easily improved to make it appropriate for university freshmen.

Non-invasive analytical technique to address water uptake on stone surfaces: The implemented Contact Sponge Method (i-CSM)

Abstract The assessment of capillary rise rate is a recommended test in Cultural Heritage diagnostics to evaluate the evolution of stone textural properties and decay, and performances of conservation treatments. Beside laboratory tests, diverse non-invasive and non-destructive, in-situ methods were developed in order to establish the monitoring for monumental structures and decorative apparatus: Karsten tube, Mirowsky pipe and contact sponge methods (CSM). The comparison between the diverse techniques demonstrated high comparability between the datasets obtained with the CSM (UNI 11432:2011) and those recast with capillary absorption. However, the dataset collected with the conventional method is affected by high standard deviation due to several variables, mainly operator-dependent. The adoption of a pocket penetrometer, coupled with the use of a thicker sponge, aimed at parameterizing the load upon the surface. The implementations allowed a higher reproducibility of the measures, as well as the possibility of applying increasing pressures. In this study the i(mplemented)-CSM was adopted to test the adsorption behaviour of a set of ornamental stones (Macigno Sandstone, Breccia Aurora, Rosso Verona and Vicenza Stone) both un-weathered and weathered by freeze-thaw ageing and salt weathering. A correlation between the maximum open pore radius and an increase in water absorbance at higher loads was established. The preliminary promising results wait to be further validated on larger datasets.

GPR/GPS/IMU system as buried objects locator

In the last years, Ground Penetrating Radar (GPR) technology has been extensively used in several different fields, including archaeology and cultural-heritage diagnostics. The integration of GPR with other positioning devices, such as a Global Positioning System (GPS) and an Inertial Measurement Unit (IMU), can significantly improve the accuracy of buried-object location, by means of an efficient control of GPR route and attitude. This article aims at investigating solutions for an accurate location of buried objects when a GPR is pulled by a terrestrial vehicle or carried by an aerial platform. In particular, a low-cost system is presented, which integrates functionalities of GPS and IMU specifically dedicated to GPR use. The device has been designed, realized and finally its performance was tested in the laboratory.

New frontiers for infrared

ÀbstractInfrared (IR) science and technology has been mainly dedicated to surveillance and security: since the 70’s specialized techniques have been emerging in thermal imaging for medical and cultural heritage diagnostics, building and aeronautics structures control, energy savings and remote sensing. Most of these applications were developed thanks to IR FPAs sensors with high numbers of pixels and, actually, working at room temperatures. Besides these technological achievements in sensors/ receivers, advanced developments of IR laser sources up to far IR bands have been achieved in the form QCL (quantum cascade laser), allowing wide band TLC and high sensitivity systems for security. recently new sensors and sources with improved performances are emerging in the very far IR region up to submillimeter wavelengths, the so called terahertz (THz) region.A survey of the historical growth and a forecast of the future developments in Devices and Systems for the new frontier of IR will be discussed, in particular for the key questions: “From where and when is IR coming?”, “Where is it now?” and “Where will it go and when?”. These questions will be treated for key systems (Military/Civil), key devices (Sensors/ Sources), and new strategic technologies (Nanotech/TeraHertz).

Integrating Non-Destructive Ion Beam Analysis Methods and AMS Radiocarbon Dating for the Study of Ancient Bronze Statues

Analytical methods based on particle accelerators are widely used in cultural heritage diagnostics and archaeological sciences from the absolute dating of organic materials by means of radiocarbon accelerator mass spectrometry (AMS) to the analysis of the elemental composition of a wide range of materials (metals, obsidians, pottery) via ion beam analysis (IBA) techniques. At CEDAD (Centre for Dating and Diagnostics), the accelerator facility of the University of Salento, AMS 14C dating and PIXE (particle-induced X-ray emission)-PIGE (particle-induced gamma-ray emission) compositional analysis in external beam mode are combined to study certain archaeological materials. We present a review of the combined application of these analytical methods in the study of casting cores of the Riace bronzes, 2 classical Greek statues of extraordinary importance for the history of art.

Laser spectroscopies for elemental and molecular analysis in art and archaeology

Spectroscopic methods using laser sources have significantly improved our capacity to unravel the chemical composition of works of art and archaeological remains. Lasers enhance the performance of spectroscopic techniques which require intense light sources and specific analytical protocols assuring a microanalytical approach for analysis has been established. This review focuses on laser spectroscopic methods used in the field of cultural heritage diagnostics. Emphasis in this work is given to the analytical capabilities of laser-based techniques for elemental and/or molecular analysis and in-situ use, spatial resolution and microanalysis. Analytical methods are classified according to the elemental (LIBS, LA–ICP–MS) and molecular (LIF/LIDAR, time-resolved absorption spectroscopy, laser desorption ionization mass spectrometry) information they yield. For non-destructive laser-induced fluorescence (LIF/LIDAR) and time-resolved fluorescence spectroscopy, imaging applications are described. The advantages provided by combined complementary techniques including but not limited to LIBS–LIF–Raman and LIBS–XRF are presented, as are recent improvements in terms of chemical imaging. Advances and applications of THz spectroscopy, non-linear spectroscopy and imaging are outlined. Finally, laser spectroscopies are described for investigations of different materials and works of art which include Bronze Age ceramics, Minoan archaeological remains, Ancient Roman buildings, Renaissance wall paintings and sculptures, and manuscripts containing iron gall inks and colorants.

Integrated non-invasive sensing techniques and geophysical methods for the study and conservation of architectural, archaeological and artistic heritage

Integrated non-invasive sensing techniques and geophysical methods for the study and conservation of architectural, archaeological and artistic heritage

Augmented Reality Applied to the Diagnostics and Fruition of Cultural Heritage

The term “Augmented Reality” (AR) is used to define integrated hardware and software technologies, designed to mix video footage taken by a camera with three-dimensional virtual objects. The result is a mix between real reality and virtual reality. Many applications of this technology are being developed for use in the field of cultural heritage and are being introduced for use in specialized contexts such as in certain phases of the diagnostic process or fruition. The basic algorithmic approach for augmented reality, starts from a video stream analysis that incorporates a real scene. Within the same scene are scattered a set of known geometric images called “markers”. When the software module in charge of the video flow analysis identifies a marker within the scene, it tries to position it in relation to a reference system integral with the chamber which performs the video shoot, and then replaces it in real time, overlapping with a 3D model achieved through a virtual modeling software. The aim of this article is to evaluate the state of the art augmented reality and then examine several experiments involving its application to cultural heritage.