Search

This study presents the petrographic and chemical characterization of the frescoes in the Church of San Panfilo in Tornimparte (AQ, Italy) by Saturnino Gatti, a prominent painter of the late 15th–early 16th century, known for his exquisite technique, composition, and use of color. The characterization of the frescoes is essential for understanding the materials and techniques used by Gatti, as well as for identifying the stratigraphy and painting phases. Eighteen samples were collected from the original paint layers, later additions (17th century), and restored surfaces, and analyzed by optical microscopy, cathodoluminescence microscopy, scanning electron microscopy (SEM-EDS), μ-Raman, and electron paramagnetic resonance (EPR). The analyses revealed a microstratigraphy often made of three main layers: (1) preparation, consisting of lime plaster and sand; (2) pigmented lime, applied by the fresco technique; and (3) additional pigmented layer on the surface. The most often recurring pigments are black, red, yellow (all generally linked with the fresco technique), and blue (applied “a secco”). The presence of two painting phases was also noted in one sample, probably resulting from a rethinking or restoration. These findings contribute to the understanding of the history and past restoration works of this cultural heritage site, providing important insights not only for conservators and restorers, but also for a broader understanding of Italian fresco painting and art history of the late 15th and early 16th centuries.

This paper presents the results obtained from the thermal analysis of a set of geomaterials (clays, pyroclastic materials, and industrial recycled materials) to be used as raw materials for the synthesis of geopolymers, specifically designed for the conservation of Cultural Heritage (CH) buildings, particularly in seismic hazard zones such as Sicily. X-ray diffraction and gas volumetric analysis (calcimetry) were applied to this set of raw materials in order to characterize the materials from the chemical and structural point of view. Thermogravimetric analysis (TG), TG coupled to Fourier transform infrared spectroscopy (TG-FTIR), and differential scanning calorimetry were used to characterize their thermal behavior. The statistical treatment of the thermogravimetric data by principal component analysis and hierarchical clustering analysis highlights the direct relation between the thermal data and the material composition that will be exploited for the selection of the best materials to obtain geopolymers specifically designed for the conservation of CH buildings.

A macroscopic lithological study and physical (hardness, size, weight) investigations, coupled with laser-induced breakdown spectroscopy (LIBS) and X-ray fluorescence (XRF) chemical analyses of three egg- and one pear-shaped polished black stones, exposed in the library of the child home of the famous poet Giacomo Leopardi, at Recanati (Italy), were carried out. They are characterized by different sizes: two with the same weight of 16.9 kg and the two smaller ones of 5.6 kg each, corresponding to multiples of standard roman weights (drachma and scrupulum). These features and the presence of some grooves on the rock artefacts, probably for grappling hooks, suggest an original use as counterweight for the four black stones herein classified as amphibole-bearing serpentinites whose lithologies are far away from Recanati (probably coming from geological outcrops in Tuscany). The four serpentinite stones closely match with the so-called Lapis Aequipondus used in antiquity by the Romans as counterweights. Due to the presence of lead rings or iron hooks in these stones, Lapis Aequipondus were also used for martyrdoms during the persecution of Christians in the Roman period, attached to the necks of martyrs that were then thrown in the wells or attached to the ankles of hanging bodies. This is the reason why these stones are also known as Lapis Martyrum, venerated with the relative martyrs, in several churches of Rome. The four black stones investigated probably arrived at Recanati from Rome after the middle of the 19th century. In the past, Christians also called Lapis Martyrum the “devil’s stones” (Lapis Diaboli). This could also be the reason for the popular belief that black stones cannot be touched by people, except those of the Leopardi dynasty. This work contributes to the cultural heritage of Leopardi’s child home, as the four black stones had never been investigated.

This work proposes a methodology of digital analysis of the state of conservation of a canvas painting to solve difficulties related to the pictorial reintegration of paintings that present an excessive number of different lacunae in terms of size and extent. The case study is related to the small-size oil on canvas painting executed by an unknown artist, where the lacunae were challenging to analyze and localize graphically. Therefore, it required a careful evaluation of the approach to be used during the pictorial reintegration intervention. Using an image analysis method, based on the semi-automatic extraction approach, the state of conservation’s graphic relief outlining different virtual operating proposals was obtained.

This paper deals with the stones used as building materials in the centre of Pisa during the Middle Age. Most of the stones are quarried from the nearby mountains, Monte Pisano and Monti d’Oltre Serchio, but there are also other ones, coming from Apuan Alps, Elba Island, western Tuscan coast, and from other quarries opened in the Western Mediterranean area. Our goal is to enrich the classic concept of street photography by inserting, in an interpretative context, the analysis and the observation of the geoenvironment in which we are immersed, daily, for the journey home-office, home-school or just for a simple walk. The tools we have are the eyes, the light and an instrument: the camera. Five stops along a city route allow to describe the main types of stones that have been used to construct and ornate the buildings since the 10th and 11th centuries, when Pisa acquired its traditional fame as one of the four historical Maritime Republics of Italy. Monte Pisano marble is the most important stone in the medieval phase of construction of the city of Pisa, often used together with black limestones to give the typical decorative alternate bands, black and white, of the Pisan Romanesque style. Other types of stones were also used, such as Quartzites, Agnano breccia, Panchina, Macigno sandstone as well as Apuan marble, granitoid rocks from Elba Island and Sardinia, and some rocks from ancient quarries of the western Mediterranean area, such as precious marbles from Greece and Turkey.

In this work, we report the results on the application of Laser-Induced Breakdown Spectroscopy (LIBS) to the analysis of coal, for the determination of its Ash Content. This parameter is critical for an efficient use of coal to produce electrical energy in power plants. The results obtained are compared with the ones obtained through conventional chemical laboratory analysis. The study here presented, although performed in the Laboratory, was set up trying to reproduce the real industrial conditions, with the purpose of easing the transfer of the results obtained to the on-line monitoring of coal quality at the power plant.

Trichrome painted wares spread out during the Middle Neolithic (between 5000 and 4500 cal. BC) along the Adriatic side of the Italian Peninsula. The pottery production was characterized by a very fine-granulated paste defined figuline and by a decoration painted with red and black colors. This research reports the results of X-Ray Fluorescence (XRF) and micro-Raman spectroscopy analysis focused on the decoration of the ceramics from two distinct geographical groups, corresponding to the village of Ripoli (Abruzzo, Central Italy) and to the Matera's caves (Basilicata, Southern Italy). A representative set of samples has been studied. XRF and micro-Raman analyses reveal that the black decoration was obtained using a black pigment based on manganese-iron oxide, whereas the red one includes iron oxides. To investigate the multilayer structure of the samples, a Monte Carlo simulation has been performed on the XRF data. The results, together with the data achieved on samples of the Serra d'Alto Culture from Matera's sites, allow to confirm previous hypotheses on the figuline production. In particular, a technological evolution is proven by the selection and control of the raw materials associated to a technologically advanced firing system. The choice of a manganese pigment is a further technological connotation of figuline potteries.

In this paper, we present a critical review on the applications of the Laser-Induced Breakdown Spectroscopy (LIBS) technique in cultural heritage and archaeology. The strategies used by the groups involved in this kind of research for the analysis of the typical materials of interest (metals, pigments, pottery, glass, etc.) are discussed in detail, as well as the use of LIBS in combination with other techniques (LIBS and Raman, LIBS and XRF, and LIBS and MS). Specific applications of LIBS as a support for cultural heritage restoration and the application of the technique for the analysis of underwater objects are presented in separate sessions. In conclusion, new trends of LIBS for cultural heritage and archaeology (micro-LIBS analysis, 3D elemental imaging, and surface- and nanoparticle-enhanced LIBS) are introduced and discussed.

3D multi-band/multi-spectral reconstruction is a technique, which allows the use of images taken in different spectral bands for the reconstruction of spectrally-resolved 3D models of paintings. In this work, we propose a procedure for constructing and comparing 3D multi-band models obtained starting from a variety of input data (RGB and IR images, UV-induced fluorescence images, etc.) and/or acquired with different instruments. The procedure has been tested on two case studies, with the aim to highlight the critical issues associated to the specificities of the subject and of the environmental constrains: a 14th century panel painting signed by Barnaba from Modena, preserved at the Museum of San Matteo in Pisa, Italy and a 15th century panel painting preserved at the Regional Gallery of Palazzo Bellomo in Syracuse, Italy. RGB, IR and UV–VIS fluorescence models obtained with a conventional digital camera (RGB and UV) and a multisband camera (IR) were realized and compared, for revealing differences at sub-millimeter level.

This paper presents the study of various Roman materials used in the construction of the Maritime Theatre, one of the main buildings in the Hadrian’s Villa complex, a designated UNESCO World Heritage Site located in Tivoli (Rome, Italy), dating to the first half of the II century A.D. The plaster layers (arriccio and intonachino) and overlying original Roman paintings that form the concave wall of the portico as well as some bedding mortars of the pyramidal stone elements (i.e. cubilia) of the circular masonry have been studied in particular. In addition, the acid volcanic rocks of the cubilia have been investigated, aiming to understand their state of alteration and geological origin. By mineralogical-petrographic microscopy (OM), diffractometry (XRPD), Raman spectroscopy, Point Load Tests (PLT), helium pycnometry, and particle size analysis, the composition and granulometric distribution of the aggregate, type and characteristics of the binder, and various physical-mechanical properties (density, porosity, water absorption, imbibition and saturation indices, mechanical resistance) of mortars and stones were defined. In addition, through digital image analysis of thin sections, the binder/aggregate ratio and some geometric characteristics of the aggregates (e.g. circularity) were determined. The research aims to improve the knowledge of the constructive technologies of the Maritime Theatre through the analysis of its materials.

Often when we approach the study of lithologies coming from the urban environment, but in general, even from any other environment, be it a quarry, a mine, an outcrop of our interest, the first study we carry out is the one in reflected-light optical-microscopy. Reflected-light microscopy in respect to transmitted-light microscopy requires minimal sample preparation, having to polish a single surface and without the need to thin the samples to allow light to pass through them. It may be useful, already in the first analysis, to try to produce quantitative data on what we are observing. A further advantage of reflected light in an urban environment is that of being able to observe and describe the formation or interaction between opaque minerals and the environment. Information that we lose by passing directly to the transmitted light. The information that can be useful to us and that we can obtain are the relative porosity of the sample, the texture (when easily recognizable in reflected light), the maximum size and shape of the edges of the grains. To all this is added the relationship between the areas of the different crystallites identified and the possible background mass, which cannot be solved on the observation scale. When we are dealing with many samples, we do not always have the time to be able to study individually sample by sample through images, so we resort to the use of image analysis tools for image segmentation and analysis. Among these, the main thresholding method with the Otsu method, the segmentation with the k averages algorithm, and, finally, a neural network of the SOM type. In this short work, we will review the main methods of image segmentation plus an innovative method developed by our group, highlighting its strengths and weaknesses.

Archeological mortars are often composed of highly inhomogeneous materials and detailed analysis in most cases can be quite difficult. In this work, a Laser-Induced Breakdown Spectroscopy (LIBS) equipment with microscopic-scale spatial resolution was used to image the distribution of elements on real archeological samples of mortars and construction material used in the foundations of the Smederevo Fortress (Republic of Serbia). A double-pulse Nd:YAG at the fundamental wavelength (λ = 1064 nm) and a CCD spectrometer coupled with a commercial microscope were used to generate the plasma and acquire the LIBS spectra. Thanks to the combined use of an unsupervised clustering algorithm and the calibration-free procedure, the results obtained show that it is possible to obtain a good discrimination between materials of different composition, allowing a quick classification for further mineral-petrographic investigations.

Digital images represent the primary tool for diagnostics and documentation of the state of preservation of artifacts. Today the interpretive filters that allow one to characterize information and communicate it are extremely subjective. Our research goal is to study a quantitative analysis methodology to facilitate and semi-automate the recognition and polygonization of areas corresponding to the characteristics searched. To this end, several algorithms have been tested that allow for separating the characteristics and creating binary masks to be statistically analyzed and polygonized. Since our methodology aims to offer a conservator-restorer model to obtain useful graphic documentation in a short time that is usable for design and statistical purposes, this process has been implemented in a single Geographic Information Systems (GIS) application.

The “Panchina” calcarenite widely outcrops along the Tuscan coastline from Livorno to Baratti (western Tuscany). It is a stone, highly porous with medium sized grains rich in organogenic carbonate fragments, mainly consisting in shells of bivalves, gastropods, and echinoderms visible to the naked eye or by using a lens. In the framework of the ongoing research on the building stones and mortars used throughout the Middle Ages in and surrounding the Pisa’s city (western Tuscany), this study focuses on the determination of the main physical and mechanical properties of “Panchina” stone samples from Livorno coast (Tuscany, Italy). The “Panchina” stone is no longer quarried and data is collected from unweathered rocks sampled from currently accessible outcrops. The data collected on twenty-eight samples from six outcrops of the Tuscan coast showed that the analysed specimens are made up of abundant calcite, subordinate quartz and feldspars, and traces of phyllosilicates. The analysed samples are characterized by medium-high porosity, highly variable water absorption by both capillarity and total immersion at atmospheric pressure, low uniaxial compressive resistance. Thanks to the good physical and mechanical properties that characterize the stone, the “Panchina” calcarenite is easy to work and extensively used in the necropolis of the Gulf of Baratti since Etruscan times and, in medieval times, in various public and religious buildings in the city of Pisa.

Raman and surface enhanced Raman spectroscopy (SERS) are established techniques allowing for fast and sensitive identification of dyes and pigments. To date, Raman has only limitedly been applied to the identification of daylight fluorescent pigments, despite this modern class of materials has been adopted by several significant artists (e.g. Frank Stella, Peter Halley, Andy Warhol, and Keith Haring). In this study, seven commercial daylight fluorescent pigments from Radiant were investigated by Raman and SERS spectroscopy. A new type of silver colloid, consisting mainly of rod-like silver nanostructures guaranteeing a high SERS enhancement, has been employed here for the first time in cultural heritage studies. As the number of fluorescent dyes suitable for the manufacturing of daylight fluorescent pigments is limited, these materials are often constituted by a mixture of dyes. Since SERS is not able to physically separate multiple dyes in mixtures, to reveal the complex composition of these materials the coupling of SERS with a separation technique proved to be mandatory. Thin-layer chromatography, being a cost-effective and fast procedure, was chosen for this purpose. The identification of each component was made possible by the comparison of SERS spectra from standard fluorescent dyes, thus increasing the available SERS database for modern materials. Lastly, the analytical protocol was applied to a modern artwork called “Rosso verde nero”, made in 1968 by the Italian artist Carla Accardi, who used to paint on plastic surfaces with fluorescent colours.

In this paper a new approach to quantitative Laser-Induced Breakdown Spectroscopy (LIBS) analysis of silicate rocks is presented. The method is adapted from the Franzini and Leoni algorithm, a method widely used in X-Ray Fluorescence analysis for correcting the matrix effects in the determination of the composition of geological materials. To illustrate the features of the new method proposed, nine elements were quantified in 19 geological standards by building linear univariate calibration curves, linear multivariate calibration surfaces (PLS) and using Artificial Neural Networks. The results were then compared with the predictions derived from the application of the algorithm here proposed. It was found that the Franzini and Leoni approach gives results much more precise than linear uni- and multivariate approaches, and comparable with the ones derived from the application of Artificial Neural Networks. A definite advantage of the proposed approach is the possibility of building multivariate non-linear calibration surfaces using linear optimization algorithms, a feature which makes the application of the Franzini and Leoni method in LIBS analysis much simpler (and controllable) with respect to the algorithms based on Artificial Neural Networks.

In this chapter we will discuss fundamental concepts and applications of self-calibrated methods for quantitative analysis by laser-induced breakdown spectrometry (LIBS). The hypotheses at the basis of the classical calibration-free (CF)-LIBS method (Ciucci et al., 1999) [8] will be critically revised and the evolution of the technique in the last two decades will be discussed, distinguishing between minor improvements or, in most cases, simple implementations of the technique and new approaches that are effectively different from the classical approach. In particular, among the alternative calibration-free methods discussed, particular attention will be given to the Monte Carlo LIBS method and the recently proposed extended C-sigma methods, which are particularly promising alternatives to standard CF-LIBS. At the end of the chapter, a very short review of the main applications of the CF-LIBS methods will be presented, with particular attention to applications where the availability of matrix-matched standards, needed for building uni- or multivariate calibration curves, are scarce (health, environment, space research, etc.).

The chemical characterization of paint material is paramount for the understanding of painting techniques, provenance studies and for assessing conservation strategies. In particular, the chemical characterization of both the organic and inorganic fraction of lakes is fundamental to assess the technologies used in their production. In this short note, we present a pilot study by comparing several micro-destructive and non-destructive methods for the comprehensive characterization of the organic and inorganic fraction of reference madder lakes. In the final procedure, the chromophores-containing molecules were separated using a sample preparation procedure based on acid hydrolysis and solvent extraction, and analysed by high-pressure liquid chromatography with UV-Vis detector (HPLC-UV/Vis). Laser induced breakdown spectroscopy (LIBS) and X-Ray Fluorescence (XRF) were used for the study of the elemental composition. Multispectral Imaging was also applied in order to evaluate its potentialities to distinguish amongst different red lakes. The final multi-technique method allowed for the characterization of both organic and inorganic fraction from the same lake micro sample.

In this work, a fast method for obtaining a quantitative elemental mapping of highly inhomogeneous samples by μ-LIBS maps is proposed. The method, transportable and cheap, allows the analysis of large maps through the use of a Self-Organizing Map clustering method coupled to Calibration-Free LIBS for quantification of cluster prototypes. The method proposed has been verified on heterogeneous materials such historical lime mortars but it can be easily applied to a larger class of inhomogeneous materials for very different applications (modern building materials, biological samples, industrial materials, etc.).

The present work aims to evaluate the alteration conditions of historical limestone rocks exposed to urban environment using the Laser-Induced Breakdown Spectroscopy (LIBS) technique. The approach proposed is based on the microscale three dimensional (3D) compositional imaging of the sample through double-pulse micro-Laser-Induced Breakdown Spectroscopy (DP-μLIBS) in conjunction with optical microscopy. DP-μLIBS allows to perform a quick and detailed in-depth analysis of the composition of the weathered artifact by creating a ‘virtual thin section’ (VTS) of the sample which can estimate the extent of the alteration processes occurred at the limestone surface. The DP-μLIBS analysis of these thin sections showed a reduction with depth of the elements (mainly Fe, Si and Na) originating from atmospheric dust, particulate deposition and the surrounding environment (due to the proximity of the sea), whereas, the LIBS signal of Ca increased in intensity from the black crust to the limestone underneath.

When compared to other analytical techniques, LIBS shows relatively low precision and, generally, high Limits of Detection (LODs). Until recently, the attempts in improving the LIBS performances have been based on the use of more stable/powerful lasers, high sensitivity detectors or controlled environmental parameters. This can hinder the competitiveness of LIBS by increasing the instrumental setup cost and the difficulty of operation. Sample treatment has proved to be a viable and simple way to increase the LIBS signal; in particular, the Nanoparticle-Enhanced Laser Induced Breakdown Spectroscopy (NELIBS) methodology uses a deposition of metal nanoparticles on the sample to greatly increase the emission of the LIBS plasma. In this work, we used a simple, fast, “green” and low-cost method to synthetize silver nanoparticles by using coffee extract as reducing agents for a silver nitrate solution. This allowed us to obtain nanoparticles of about 25 nm in diameter. We then explored the application of such nanoparticles to the NELIBS analysis of metallic samples with a mobile LIBS instrument. By adjusting the laser parameters and optimizing the sample preparation procedure, we obtained a NELIBS signal that is 4 times the LIBS one. This showed the potential of green-synthetized nanoparticle for NELIBS applications and suggests the possibility of an in-situ application of the technique.

Within a major framework of studies around artificial weathering and its effects on different lithotypes, in this work we study the effects of thermal stresses after artificial thermal decay on different types of stones used in historical buildings: a sandstone, a calcarenite and a marble. The sandstone belongs to the so called “Macigno” Formation and mainly outcrops along the northern Apennine (North Western Tuscany) and it has been widely used around Tuscany for building purposes (e.g., in Florence, Lucca, Pisa, Pistoia, etc.); the analysed calcarenite (Gravina) comes from the surrounding of Matera Town and has been deeply used for the construction of the ancient buildings of the town itself; and the marble comes from the Carrara marble district (Northern Tuscany), a highly used stone throughout the centuries as ornamental stone. All these types of stone for their physical and mechanical properties, and aesthetic appearance, have been extensively used as both ornamental stones and as construction materials. To reproduce a plausible effect of natural thermal decay of the stones due to day-to-night and season-to-season fluctuations, we subjected the samples to artificial thermal decay. We carried out different thermal cycles on the samples by using a stove at 150°C and a muffle furnace at 300°C and 450°C. We analysed the physical and mechanical properties before and after each cycle to compare and evaluate the effects of thermal stresses on the stones. Among the different analyses: mass and volume measurements, water absorption tests, mercury intrusion porosimetry, thin-section observations and determination of chromatic alterations through image analysis and Munsell charts method. It was then possible to evaluate the influence of both mineralogy and microstructures on thermal decay of the studied stones (variations in fabric and modifications on physical and mechanical properties).

In this work, marbles from Castagneto Carducci (Livorno province, Tuscany), which originated by contact metamorphism of the Calcare Massiccio Fm., an Early Jurassic limestone belonging to the Tuscan Sequence, were studied for determining their chemical, mineralogical and petrographic characteristics, and the main physical and mechanical properties. Forty marble samples were sampled and analysed; they are from two inactive quarries on the NW and NE slopes of the Mt. Romitorino, and from natural outcrops in the vicinity of the quarries. The analysed rocks are marbles with high calcite content (> 98% by weight). Optical microscopy observations showed Castagneto Carducci marbles generally have a heteroblastic/granoblastic texture with crystal boundaries from curved-right to lobate. The maximum grain size of the calcite crystals ranges from 0.2 mm to 0.6 mm. The determination of the main physical and mechanical properties of the analysed marbles showed that these rocks are characterised by low porosity and, in general, good physical and mechanical properties.

In this paper we present the application of Independent Component Analysis to a set of time-resolved LIBS spectra, acquired on a brass sample at different delay times. The decomposition of the LIBS spectra in few Independent Components with a given temporal evolution is then exploited for obtaining the temporal evolution of the plasma electron temperature, through the application of the three-dimensional Boltzmann plot method recently proposed by the authors. This method allows the determination of the electron temperature temporal evolution without any knowledge of the spectral parameters (transition probability, degeneracy of the levels, etc.…) of the emitting lines. Only the knowledge of the energy of the upper level of the transition is required. The reduction of the LIBS spectral dataset to few Independent Components and associated proportions, further simplifies the determination of the plasma electron temperature temporal evolution, since the intensity of the emission lines does not need to be calculated. The results obtained are compared with the ones obtained using classical two-dimensional Boltzmann plot approach.

Every year throughout the world > 50 million vehicles reach the end of their life, producing millions of tons of automotive waste. The current strategies for the separation of the non-ferrous waste fraction, contain mainly aluminum, magnesium, zinc and copper alloys, involve high investment and operational costs, and pose environmental concerns. The European project SHREDDERSORT, in which our research group was actively involved, aimed to overcome this issue by developing a new dry sorting technology for the shredding of non-ferrous automotive wastes. This work represents one step of the complex SHREDDERSORT project, dedicated to the development of a strategy based on Laser Induced Breakdown Spectroscopy (LIBS) for the sorting of light alloys. LIBS was here applied in laboratory for the analysis of stationary aluminum shredder samples. To process the LIBS spectra a methodological approach based on artificial neural networks was used. Although separation could in principle be based on simple emission line ratios, the neural networks approach enables more reproducible results, which can accommodate the unavoidable signal variations due to the low intrinsic reproducibility of the LIBS systems. The neural network separated samples into different clusters and estimates their elemental concentrations.

In this communication, we present the development of the first double-pulse micro-LIBS (DP-μLIBS) instrument for three-dimensional compositional mapping of materials. The system allows for high-resolution three-dimensional scanning of materials; its advantages with respect to conventional single-pulse micro-LIBS systems are described and discussed. As a test example, we analyzed three Euro coins to show the performances of the system on homogeneous samples (20 Eurocents), heterogeneous samples (1 Euro) and layered samples (5 Eurocents). DP-μLIBS cannot provide isotopic information and has, typically, limits of detection for the elements of interest much higher with respect to Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS). However, when the isotopic information and the extreme sensitivity to trace elements is not be necessary, the results obtained show that DP-μLIBS can be a viable alternative to LA-ICP-MS for the acquisition of high resolution three-dimensional compositional maps.

In this paper, we present a discussion on three different methods recently proposed for the analysis of Laser-Induced Breakdown Spectroscopy (LIBS) spectra, namely the One-Point-Calibration, the Calibration-Free Inverse method, and the Csigma graphs approach. The common characteristics of these methods is the fact of being based on the main equations governing the emission of near-LTE plasmas, i.e. the same theoretical framework that is at the basis of the Calibration-Free LIBS analysis. However, with the purpose to guarantee a higher trueness in the analysis, these methods rely on the information obtained by the analysis of a single reference material, of known composition, for calculating the values of some experimental parameters that would be otherwise difficult to determine. In analogy with a similar approach used in the analysis of X-ray Fluorescence spectra, we place these techniques in the general framework of the so-called Fundamental Parameters Analysis. The three methods were tested and compared on LIBS spectra acquired on modern bronze samples. The advantages and drawbacks of the different approaches are discussed in detail.

Detection of natural organic dyestuffs in art objects is a challenge for scientists and conservators, as it is limited by severe sampling restrictions. This work is aimed at developing a sampling-free method for the analysis of colorants traditionally used in historical textiles, with a focus on the preservation of the sample integrity to enable its further characterization with other techniques. Thus, in this study, Surface Enhanced Raman Spectroscopy (SERS) was performed directly on laboratory-dyed textiles for the identification of anthraquinone dyes, generally characterized by strong fluorescence signals that hinder conventional Raman spectra. For this purpose, SERS-active silver nanoparticles were produced by Pulsed Laser Ablation in Liquid (PLAL). PLAL presents some advantages when compared to conventional chemical preparation methods, namely the absence of reagents in the suspension and a stronger control over the nanoparticles morphology that can be obtained by changing the ablation conditions. For the analysis, a small piece of fiber was gently rubbed on a microscope glass slide where few drops of Ag nanoparticles were previously deposited and preconcentrated; micro-Raman measurement followed. To ensure the suitability of the analytical strategy for the characterization of historical artworks, the reversibility of the treatment was demonstrated by Laser Induced Breakdown Spectroscopy analysis of a wool fiber treated with nanoparticles and gently cleaned with diluted sodium citrate (p H 6-7).