Micro-destructive Techniques Research Articles

Disclosing Colors and Pigments on Archaeological Objects from the Aga Khan Necropolis (West Aswan Egypt) through On-Site Analytical Methods: Preliminary Results

The present study is aimed at the characterization of artifacts excavated in the necropolis surrounding the mausoleum of the Aga Khan in Aswan (Egypt), as part of the Mummies Investigations Anthropological & Scientific West Aswan Necropolis (MIASWAN) project. Four cartonnages and some pottery shards were investigated on-site by means of non-destructive and micro-destructive techniques, such as attenuated total reflection/Fourier transform infrared spectroscopy (ATR/FTIR) and visible reflectance spectroscopy Vis-RS). Thanks to the use of these techniques, several pigments employed in the creation of the artifacts were identified. Due to the impossibility of transporting the investigated objects out of Egypt, a first-ever on-site characterization of the artifacts from this important excavation was carried out through scientific methodologies. These extreme conditions made the use of analytical instrumentation very challenging. Nevertheless, several characteristic pigments and hues were successfully identified.

Towards high-resolution water isotope analysis in ice cores using laser ablation - cavity ring-down spectroscopy.

A new micro-destructive technique for high-resolution water isotope analysis of ice samples using a Laser Ablation (LA) system coupled with a Cavity Ring Down Spectrometer (CRDS) is presented. This method marks the first time water isotope analysis is conducted directly on the ice, bypassing the traditional steps of melting and vaporizing the ice sample, thanks to the direct transition of ice into water vapour through the laser ablation process. A nanosecond ArF laser ablation system (193 nm) with an integrated two-volume ablation chamber was successfully coupled to a CRDS analyzer, utilizing nitrogen as the carrier gas. The application goal is the use of LA-CRDS for ice core studies, so a method for preparing ice standard samples using liquid water isotope standards, widely used for ice core analysis, is introduced. The measurements were conducted in a discrete mode, by performing laser ablation raster scans of 4 mm × 4 mm areas, establishing a sampling resolution of 4 mm along an ice core's depth. The water vapour concentration reaching the CRDS analyzer as well as the quality of the water isotopic measurements of δ18O and δD were influenced by laser parameters, such as laser spot size, repetition rate, laser fluence, ablation time as well as by the flow rates of the carrier gas. After optimizing the experimental conditions for water vapour formation, three ice standards samples were analyzed for calibration purposes on the VSMOW-SLAP scale and a section of an ice core sample was also tested. Critical parameters influencing the precision and accuracy of water isotopic measurements were investigated, and isotopic fractionation phenomena were identified, pointing to essential considerations for the technique's further development.

Physicochemical structure and micromechanical properties of archaeological wood under alternating dry and wet conditions

ABSTRACT The relationship between physicochemical structure and micromechanical properties of archaeological wood is not understand. For this purpose, the study took the archaeological wood from the Shahe Ancient Bridge site as an example. The physical properties, microstructure, chemical composition, and micromechanics of archaeological wood were evaluated using non-destructive and micro-destructive techniques. The results indicated that the deterioration of Phoebe sp. wood was more severe than that of Abies sp. wood. However, the basic density of Phoebe sp. wood was higher than that of the control sample due to the collapse of cell walls. The cell walls exhibited a variety of destructional forms, such as cavities and collapses, caused by decay fungi and erosion bacteria. The cell cavities and cell walls deposited inorganic substances. Furthermore, hemicellulose and amorphous cellulose were preferentially degraded before crystalline cellulose was degraded, and S-type lignin was more prone to degradation compared to G-type lignin. Due to the changes of cell wall structure, the hardness of the cell walls increased while the elastic modulus of the cell wall decreased significantly. This study may provide a reference for the study of the relationship between cell wall structure and micromechanics of archaeological wood.

Building materials and decay assessment of the Gerace Cathedral (Reggio Calabria, Southern Italy)

A multi-analytical approach was employed for the first time to study the stone materials, wall paintings and related degradation forms in the Cathedral of Gerace (Reggio Calabria, southern Italy). With an area of around 1898 square meters, the Gerace Cathedral is the largest in Calabria: its construction dates back to the Norman era (between 1085 and 1120), and currently displays distinct features of Greek and Latin architectural orders. Despite having undergone numerous restorations, the church perfectly preserves its original buildings materials. Following an extensive site inspection campaign, supported by the experts dealing with building restoration, several areas were selected for analyses. Both in situ investigations and laboratory tests were carried out on micro-fragments using Non-Destructive and Micro-Destructive Techniques (NDTs and MDTs). The first step involved an inspection through InfraRed Thermography (IRT) in order to map the internal walls of the Cathedral and identify zones with potential degradation phenomena. Subsequently, a more in-depth study was designed based on the thermographic results, and laboratory tests were carried out on micro-fragments and powders to characterize the different kinds of materials (i.e., stones, mortars, plasters and pigments) and decay agents (i.e., salts and efflorescences). Thirty-one samples were subjected to a complementary analytical approach which included Polarizing Optical Microscopy (POM), Ion Chromatography (IC), X-Ray Powder Diffraction (XRPD) and Scanning Electron Microscopy (SEM) coupled with microanalysis (EDS). The results allowed us to preliminarily characterize the different materials from which the Cathedral was built, determine its state of conservation and provide a better knowledge of the entire building, revealing details not visible to the naked eye which are important for future conservation interventions. As for the state of conservation, the integrated use of various techniques enabled the detection of rising damp generally correlated with the occurrence of water infiltration and migration phenomena which appear to affect a large part of the building, causing noticeable damage (i.e., loss of surface material, micro-cracks, white salt efflorescence, etc.). The characterization of the materials carried out on mortars, plasters, and pigments also confirmed the local origin of the raw materials. However, the provenance of the studied marbles and crystalline limestones, could not be established and, therefore, further in-depth studies are required.

High performance liquid chromatography as a micro-destructive technique for the identification of anthraquinone red dyestuffs in cultural heritage objects

Abstract This article describes two of the most common natural sources of red anthraquinones that have been used since antiquity for textile dyeing and as lake pigments, namely cochineal insect and the roots of Rubia and Relbunium plants. Carminic acid is the main component of carmine, the red colorant obtained from cochineal. Alizarin and purpurin are found in the extracts of Rubia roots, but Relbunium roots contain only purpurin. These red anthraquinones have been identified in a variety of cultural heritage objects. High performance liquid chromatography with diode array detection (HPLC-DAD) is described as the most suitable analytical technique for the identification of these dyestuffs, particularly in micro-samples from textiles or pigment layers in paintings and polychrome sculptures. Finally, application of HPLC-DAD analysis to the identification of lake pigments in micro-samples of mural paintings of two eighteenth century Andean churches in Peru is described.

Micro-destructive evaluation of the mechanical properties of lime-based mortars

In every restoration project, knowledge of the mechanical properties of the original materials is considered essential for engineers, not only for the structural assessment of the monument, but also for the selection of compatible restoration materials. In the case of mortars, however, direct or indirect determination of their mechanical properties is usually challenging, due to the limited size and number of available samples. Hence, alternative non- or micro-destructive techniques need to be exploited for the evaluation of the compressive and flexural strength of historic mortars. In this study, the micro-destructive scratching resistance test is used to assess the compressive and flexural strength of a variety of lime-based mortars, that were either designed and produced in the laboratory using different binders, aggregates and admixtures, or sampled in-situ. Sound linear correlations observed between the intrinsic specific energy, resulting from the scratching resistance test, and the compressive and flexural strength of the laboratory designed and produced mortars validate the potential of the scratch tool in assessing the aforementioned mechanical properties of lime-based mortars. This is further confirmed by results on historic mortar fragments. Therefore, the use of the novel micro-destructive scratch tool is recommended in cases where lime mortar sampling is limited, in order to provide reliable estimates for the mechanical properties of historic mortars.

Polychromy in Roman Portraits from Asido (Medina Sidonia, Cádiz, Spain). Livia, Germanicus and Drusus Minor

This paper presents a recent study on a Roman period marble sculpture depicting Empress Livia and the portraits of Germanicus and Drusus Minor, found at the praesidium of Asido (Medina Sidonia, Cádiz, Spain). The sculptures retain extensive evidence of their original polychromy. The properties and spatial distribution of these pigment remains were investigated by portable non-invasive and micro-destructive techniques, applying digital microscopy, and UV/VIS/NIR/SWIR spectroscopy, portable XRF and SEM–EDS analysis. The study revealed the presence of Egyptian blue and ochre on Livia’s mantle and charcoal black on Livia’s eyes and hair, remains that were not clearly visible to the naked eye. This is a significant approach, used to identify colours on ancient marble sculpture, which transforms our understanding of these unique pieces. Elemental composition analysis by pXRF has confirmed the evidence of pigments, furthermore supported by the Raman results, making it possible to develop and reconstruct the colour palette that originally brought these sculptures to life in vibrant polychrome. The research offers a new methodology for identifying pigments on marble sculpture and opens new ways for investigating other types of material culture aided by the development of the analytical equipment mentioned.

Historically Accurate Reconstruction of the Materials and Conservation Technologies Used on the Facades of the Artistic Buildings in Lecce (Apulia, Italy).

The protection of the stone surfaces of the buildings of the city of Lecce (Apulia, Italy) represents an ancient practice, which has always allowed the conservation of the historical-artistic heritage of the city, which nowadays is an international touristic and cultural destination. The identification of ancient recipes, materials and methodologies for the protection of historical buildings plays an important role in establishing correct protocols in order to ensure the durability of stone surfaces over time. This work presents a historically accurate reconstruction of the materials and conservation technologies used on the facades of the artistic buildings in Lecce. Several historical buildings, both civil and religious, have been selected in order to investigate the treatments applied on their facades and to know the traditions spread in the past in the field of building conservation in the Salento territory. Thanks to non-invasive or micro-destructive techniques (optical microscopy, ATR-FTIR spectroscopy, pyrolysis–gas chromatography–mass spectrometry), the characteristic molecular markers of the materials and the products of degradation have been identified, deepening the knowledge of the mechanisms of deterioration and interaction between the stone material, the surface finish and the surrounding environment. The paper is a valuable tool for the knowledge of ancient traditions and the planning of proper restoration works.

Textile Museum Collections. SIM Method Validation for the Assessment of Pesticides

In time the environmental conditions could damage textiles (materials/ artifacts) causing the need to develop better non-destructive or at least micro-destructive analysis techniques of the samples. There are ethnographic textile artifacts that were treated in the past with various pesticides, that have not been mentioned in any document. These are often re-treated with chemicals by museum staff as a method of preventing pest infestation. Due to the progressive use of many pesticides, this paper was focused on the detection and quantification of three pesticides: malathion, methoxychlor, and permethrin (cis- and trans- isomers). Gas chromatography is one of the most widely used analytical techniques for characterizing volatile organic compounds and therefore was the analytical method of choice for the present study. Because these analytes are found at trace levels, the detection and quantification limits of analytes are very small and it is necessary to optimize and validate a SIM method - that allows the mass spectrometer to detect specific compounds with high sensitivity. In SIM mode, the instrument is set to collect data at selected masses of interest, thus increasing the accuracy and precision of the quantitative results. The present paper is aimed to develop this type of method with specificity and selectivity, high precision (expressed in terms of repeatability and intermediate accuracy), accuracy, suitable working range and linearity, and high degree of series� homogenity.

Decay Assessment of Stone-Built Cultural Heritage: The Case Study of the Cosenza Cathedral Façade (South Calabria, Italy)

This study aims to assess the different decay phenomena affecting the Cosenza Cathedral façade (Calabria, South Italy) through the evaluation of the relative damage indices. For this goal, a multidisciplinary approach was applied exploiting both nondestructive and microdestructive techniques. Such a combination enabled proposing an intervention priority scale that can be helpful to institutions when planning a prompt restoration intervention. The results suggest the efficiency of this approach to obtain a multidisciplinary diagnostic and conservation system for the management and valorization of the Cultural Heritage also in terms of monitoring, maintenance, and selection of the most suitable restoration procedures over time.

Identification of minerals and mineral pigments in lacquer by the comprehensive comparative analysis of spectroscopy information

This article presents the results of a systematic investigation on the identification of minerals used in lacquers. Micro-Raman combined with Infrared spectroscopy can serve as a highly specific and complementary micro-destructive technique for successfully identifying the molecular structure of the minerals. Both 532-nm and 785-nm laser radiations were used to compare the spectral information and to clarify which wavelength was suited to balance the signal to noise ratio. The spectra of fourteen minerals were analyzed and compared in detail, which can provide support for the research on the developmental changes of lacquer materials in different historical periods by establishing an identification method.

Spectroscopic characterization of xx century mural paintings of punta begoña’s galleries under conservation works

A multi-analytical approach based on the combined use of non-destructive spectroscopic techniques and micro-destructive techniques is presented, not only to characterize the mural paintings of Punta Begoña galleries (Getxo, Biscay, Spain), but also to fill the gaps found in the historical documentation. The galleries were built in 1918 for Horacio Echevarrieta, a spanish republican businessman, and are in the list of protected historical buildings of the Basque Country. The whole building is composed by two galleries and a main hall with francoist iconographies in their walls, which disagree with the owner’s ideology, painted around 1938 after the occupation of the building in the Spanish Civil War. There is a lack of historical information about the original aspect of the mural paintings (1918 decoration) or the nature of the observable paintings (1938 over paintings). Thanks to the analysis carried out by optical microscopy, Raman spectroscopy, X-ray fluorescence (XRF), Fourier Transform Infrared spectroscopy (FTIR), Scanning electron microscopy coupled to electron scattering X-ray spectroscopy (SEM-EDS) and X-ray diffraction analysis (XRD), it was possible to identify under the painted layers a lead white preparation layer. Then, the original mural pigments were identified being of a silicate nature due to the systematic presence of presence of Clinochlore in all the colours. Regarding the over painted panels, their characterization revealed pigments that did not fit with the contemporaneous pigments, common practice in the francoism regime. In addition, carnauba wax could be identified as the binder. Moreover, the main decaying pathways of the materials were pointed out. These results will help to provide a new vision of these mural paintings, and the whole building. However, the most important achievement was the historical contextualisation of the main hall, which could help to change the historical perception of this heritage, putting the analytical chemistry at the service of history.

Detection of bronze paint degradation products in a contemporary artwork by combined non-invasive and micro-destructive approach

Conservation of contemporary art requires deep knowledge of techniques and materials used, in order to assess their decay rate and identify the proper way to preserve art objects; scientific investigations are thus fundamental for conservation purposes. This paper presents a multi-analytical approach based on the use of both non-invasive and micro-destructive techniques for the study of a contemporary artwork from the Italian artist Paola Levi-Montalcini. Object of this work is Nel Deserto, made in 1966 using several different modern materials. The mixed-media nature of the artwork required a complete characterization of the materials, preliminary to the challenging conservation intervention. Before the intervention, Nel Deserto was in fact showing severe signs of degradation, which prevented it from being exposed to the public. The analytical approach was based on the preliminary use of portable microscopy and XRF, followed by micro-FTIR on diamond cell and low-pressure SEM-EDS and allowed achieving fundamental information on the materials while not harming visibly the artwork. The interaction between a transparent film (made of a poly(vinyl chloride) copolymer) and a bronze-based paint, triggered untypical degradation phenomena. The loss of hydrochloric acid from the chlorine containing polymer led in fact to the formation of dark green colored copper halides, which irremediably altered the artwork.

The provenance of obsidian artefacts from the Middle Kingdom harbour of Mersa/Wadi Gawasis, Egypt, and its implications for Red Sea trade routes in the 2nd millennium BC

This paper presents the results of the geochemical analysis carried out on the obsidian artefacts discovered at the archaeological site of Mersa/Wadi Gawasis, located along the Egyptian Red Sea coast, in between the modern cities of Safaja and Quseir. During the 12th and 13th Dynasties of Egypt the site hosted a port city from where the Egyptian expeditions set sail directed to the south, on both edges of the Red Sea. Six obsidian artefacts collected during the 1970s’ research carried out at the site by A. Sayed, were geochemically analysed, together with five geological samples from the obsidian Kusrale source in Eritrea. The major element concentrations were determined by SEM-EDS analysis and the trace element concentrations were obtained by LA-ICP-MS method, a micro-destructive technique, capable of chemically characterizing the volcanic glass. A comparison of geochemical results obtained on the archaeological artefacts and geologic samples, together with the literature data on different geological obsidian outcrops from the Horn of Africa and the southwestern Arabian peninsula, allowed us to determine the provenance of the Mersa/Wadi Gawasis obsidian artefacts in both the Kusrale source of Eritrea, and the volcanic area of Dhamar Reda in Yemen. These results can provide further insights on ancient trade routes along the Red Sea during the early second millennium BC.

Assessment of protection treatments for carbonatic stone using nanocomposite coatings

In this paper the effect of the application of four kinds of polymer dispersions containing nanoparticles, used as protectives, on two type of carbonatic lithotypes, White Noto and Comiso stone, is reported. The study was conducted by analysing the contribution of each component of the system. After the structural characterization of the coating itself, the performance of those colloidal systems has been studied upon application on the calcarenites, preferring non-invasive techniques and microdestructive techniques. Effect of the nanoparticles presence on hydrorepellency and roughness of the stone surface and on chromatic changes has also been considered. The tests conducted have proven that although some of the formulations present some issues for their usage on White Noto stone, all four formulations induce an effective waterproofing action on Comiso stones, even in presence of TiO2 and SiO2 nanoparticles.

Pigment identification on Campana reliefs from the Palatine Hill and Colosseum Valley in Rome

This article shows the first pigment identification of the Campana reliefs , Roman architectural earthenware plaques. The Campana reliefs polychromy were investigated by applying a multidisciplinary approach involving non-invasive and micro-destructive techniques to some fragments with traces of colour found on the north-eastern slopes of the Palatine Hill in Rome. X-ray fluorescence analysis and reflectance measurements provided preliminary identification of pigments, which was subsequently confirmed by X-ray diffraction and elemental mapping by scanning electron microscopy-energy dispersive spectrometry carried out on micro-samples and cross sections, respectively. Yellow ochre, red ochre, lead white, calcium-based white pigment, Egyptian blue and minium were identified. In addition, PIL (Photo Induced Luminescence) imaging was performed, identifying the macro-distribution of Egyptian blue, even on plaques without visible traces of colour.

Geochemical and mineralogical relations of three ceramic complexes from the formative period (2000–300 BC) in Costa Rica

The formative period in Costa Rica (2000–300 BC) refers to the consolidation of agricultural practices, the appearance of pottery, and the beginning of a village lifestyle. In this context, ceramics are of interest as they lack fundamental surveys with analytical techniques to understand the relations among the ceramic complexes and their technology. Eighty-one ceramic samples from three complexes of the formative period in Costa Rica were analyzed with micro-destructive techniques such as X-ray diffraction (XRD) and proton-induced X-ray emission (PIXE). Information about the mineral and elemental composition was thus gathered, followed by principal component analysis (PCA) leading to hierarchical clustering in dendrograms. We explored the correlation of ceramic complexes Tronadora, Chaparron, and La Montana through studying their elemental composition, minerals, and geological features. Each complex was examined with a dendrogram of its elemental composition to assess the correlation of ceramic forms within the complex. Based on the association found among these ceramic forms for each complex, we suggest that the Tronadora and Chaparron complexes had access to more than one source of raw materials. Such findings are related to the geology of the zone and the minerals discovered near each site. PCA shows a close association between Tronadora and Chaparron with elements such as Cl and Pb, as opposed to La Montana in which Rb, Fe, Zn, and Cu were present. Our investigation provides technical evidence for some archeological hypotheses proposed for the interaction among these three ceramic complexes.

In situ investigation of stone heritage sites for conservation purposes: a case study of the Sz\xe9kesfeh\xe9rv\xe1r Ruin Garden in Hungary

This paper demonstrates the application of in situ diagnostic tools to document stone heritage sites prior to conservation interventions using a Medieval ruin of Central Europe (Székesfehérvár, Hungary). The applied methods included lithological mapping and characterisation and mapping of decay forms as well as in situ measurements of physical parameters such as Schmidt hammer rebound, moisture content and micro-drilling resistance. The combination of these methods allowed the condition assessment of different lithotypes and demonstrated the role of micro-fabric, mineralogical composition and climatic conditions in stone durability. Differences were found in the properties and in the weathering forms of fine-grained and medium-grained porous oolitic limestone and travertine. The black crust observed in porous limestone is less prone to detachment on medium-grained oolitic limestone ashlars, while scaling was observed on fine-grained oolitic limestone blocks. The micro-drilling resistance of exposed porous limestone showed higher drilling resistance at the crust zone (upper 1–2 mm) than below, marking the upper cemented zone, while the drilling resistance of porous limestone under shelter showed an opposite trend. The shelly limestone, the sandy calcarenite and red compact limestone also showed an increase in drilling resistance at the topmost app. 2 mm zone. The applied in situ, non-invasive and micro-destructive techniques helped in the identification of endangered zones at Székesfehérvár, thus, they can provide key information on condition assessment of stones at heritage sites, where sampling is limited and preventive conservation is important.

Portable Vis-NIR-FORS instrumentation for restoration products detection: Statistical techniques and clustering

The identification of modern restoration products with portable instrumentation will enable conservators and conservation scientists to gain information in a shorter time and at a reduced cost, compared to standard micro-destructive techniques. This study employs portable Visible Near-Infrared Fibre Optics Reflectance Spectrometry (Vis-NIR-FORS) as a diagnostic tool to identify and classify the considered products. We assembled a large library made of the most commonly used industrial products in the field of cultural heritage. Thirty products were applied in different concentrations on different substrates (e.g., marble, mortar, polychrome plaster, modern mural painting), and mock-up samples were investigated through Vis-NIR-FORS in the 350–2200 nm range. We then applied several statistical techniques and modern machine learning algorithms such as clustering to the entire database, to quantify the degree of correlation among different spectra. We show how using a multivariate, robust statistical approach can increase the signal-to-noise ratio, thus leading to a more precise identification and localisation of these products. Finally, the proposed procedure was also applied to spectra collected in situ on mural paintings.

Elucidating the composition and the state of conservation of nitrocellulose-based animation cells by means of non-invasive and micro-destructive techniques

Abstract This paper presents the first study on Rodovetri, animation cels produced between the 1950s and the 1970s for the Italian television and conserved at the Museum of Industry and Labour “Musil” (Italy). Although these cels are considered as works of art and witnesses of Italian animation design, they have never been studied before. The study of one of the most endangered cel groups of the Musil collection is presented here. The main aims were to investigate the composition of these animation cels, to identify the materials used for painting the characters, and to assess the state of conservation of the cels. The results, which were obtained by means of a multi-analytical non-invasive and micro-destructive approach, underline the composition of the plastic substrate as nitrocellulose, while the painted layers – which contain a variety of pigments and dyes – were found to be bound with a mixture of plant gum and animal glue. This study also provides information on their state of conservation, in particular in relation to the de-nitration of plastic sheets. Important issues on the preventive conservation are also raised.