The Source Materials for Lime Production in the Monte Pisano Area (NW Tuscany, Italy)

In the Monte Pisano area (north-western Tuscany, Italy) several limestones outcrop and some of them are carbonate-rich rocks that were used for air-hardening lime or hydraulic lime production. Since Roman times, carbonate rocks outcropping in the Monte Pisano area have been used for that purpose. Monte Pisano is a mountainous system of modest size that is part of the Tuscan Apennine, located in the north-western part of Tuscany, and it separates the two cities of Pisa and Lucca. As an obvious consequence of the presence of good source rocks useful for the production of lime, in the surroundings of Monte Pisano there was a great use of carbonate rocks for the production of aerial lime and hydraulic lime. In fact, the monumental buildings in the Middle Ages were built making extensive use of binding materials obtained by firing rocks belonging to formations of the Tuscan metamorphic sequence: the Monte Pisano marble and the Selciferous Limestone. Several famous monuments in Pisa’s Miracle Square and in Lucca’s historical centre were built by using air-hardening lime and hydraulic lime obtained by firing these rocks. The aim of this work is to characterize samples from the Monte Pisano quarries, where the aforementioned carbonate-rich stones were quarried to produce airhardening lime and hydraulic lime, by mean of chemical, mineralogical and petrographic studies and by determining their physical and mechanical properties. These same properties will also be determined on handmade mortar samples made up of self-produced binders and normalised sand to evaluate the best uses, and the optimum time and temperature of stone firing

LIBS analysis to define the alteration processes on the surface of ancient stones: the case study of Romanesque medieval monuments (Italy)

Weathering and bio-deterioration processes frequently affect the chromatic aspect of the stones used in the monuments. The surface alteration involves both physical modifications (e.g., increase of porosity) and chemical-mineralogical transformations of the rock, with formation of new secondary phases and deposition of the organic substances and inorganic solid phases (amorphous or crystalline particles). This research aims to study the surface films of stones (i.e., basalts, pyroclastic rocks, limestone, marbles) used in some historical-cultural relevant Sardinian Romanesque churches (XI-XIV sec.) using LIBS and XRD analysis. These latter, together with petrographic analysis by polarized light microscopy in thin section, are useful to reconstruct the micro-stratigraphic aspects of different film levels. The results highlight three different cases: i) chromatic alteration of the stone surface, ii) chemical-mineralogical alteration of stone with formation of coatings similar to the stone substrate, iii) chemical-mineralogical processes with the formation on the surface of secondary phases not related to the substrate, with the presence of Ca-oxalate (i.e. weddelite, whevellite). The presence of the Ca-oxalates, as noted in literature, is a testimony of application of organic substances on the surfaces themselves, with aesthetic purposes, to standardize or improve the color of the stone, or conservative, to limit the negative effects of weathering

Evaluation of potsherds features using hyperspectral maps generated by μ-LIBS scanner

The micro-laser induced breakdown spectroscopy (µ-LIBS) technique allows performing fast elemental analyses, without sample preparation and thus making it specifically useful in the analysis of the composition of ancient potsherd. The µ-LIBS instrument is equipped with a microscope and a scanning system allowing to realize small craters (about Ø = 25 µm) in order to obtain detailed hyperspectral surfaces maps (up to a maximum size of one square centimeter). The data are processed by Self-Organizing Maps (SOMs) method to visualize in 2D representations allowing significant information on the technological features of ceramic samples.The micro-laser induced breakdown spectroscopy (µ-LIBS) technique allows performing fast elemental analyses, without sample preparation and thus making it specifically useful in the analysis of the composition of ancient potsherd. The µ-LIBS instrument is equipped with a microscope and a scanning system allowing to realize small craters (about Ø = 25 µm) in order to obtain detailed hyperspectral surfaces maps (up to a maximum size of one square centimeter). The data are processed by Self-Organizing Maps (SOMs) method to visualize in 2D representations allowing significant information on the technological features of ceramic samples

PROTEUS: an immersive tool for exploring the world of cultural heritage across space and time scales

AbstractIn the field of digital humanities, it is increasingly necessary to develop and validate virtual reality tools that are capable of combining various scientific data in a virtualized context providing also access and user friendly consultation of online repositories. This paper reports the main aspects of the implementation of a virtual reality tool integrated with an online repository for storing 3D models, metadata and chemical analyses related to different sectors of digital humanities. The virtual reality software, developed for the Oculus Quest 2 hardware, is called PROTEUS and allows for seamless transition from the macroscopic world of digital humanities to the microscopic world of molecular sciences. The paper illustrates, by means of some case studies, the performances of this innovative tool that permits the researcher to understand and manipulate objects, to test hypotheses and to seek meaningful results, visualising the metadata while changing the parameters of the simulation in a dynamic and interactive way. This represents also a significant step forward in the democratisation of science, thanks to an user-friendly and immersive access to advanced scientific algorithms, which allow the natural perception of structural and topological features of the underlying molecular and supra-molecular systems. Graphical Abstrac

Mineralogical, petrographic and physical-mechanical study of Roman construction materials from the Maritime Theatre of Hadrian's Villa (Rome, Italy)

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

Micro-chemical evaluation of ancient potsherds by μ-LIBS scanning on thin section negatives

In the study of ancient pottery, thin section analysis represents the basic approach to study mineralogical and petrografic features in order to obtain preliminary information about the production technology and origin of archaeological ceramics. However, even if thin section analysis allows investigating the textural and structural characteristics of potteries, peculiar features related to clay paste and temper composition, as well as provenance issues, can be detailed addressed only by quantitative mineralogical and chemical studies. In the realization of thin sections, a negative face is always produced, similar to the thin section itself; these remains can be used for additional analyses, such as high spatial resolution micro-chemical studies using, for example, a micro-laser induced breakdown spectroscopy (LIBS) scanner. LIBS is a spectroscopic technique that, exploiting the laser radiation, is able to bring into the plasma state micrometric portions of the sample, and to analyse its content through the study of the optical emission of the plasma itself. Unlike other techniques, LIBS can detect and quantify also light elements such as aluminium and magnesium. Images produced by the micro-LIBS instrument show the spatial distribution of the chemical elements within a portion of the sample, which may have dimensions from a few hundred microns up to several centimeters. The combination of these images with algorithms derived from image processing techniques may return interesting information and supporting data to in-depth investigate pottery components detected by optical microscopy observations. In this work, we present the results of an experimental study performed on thin-section negatives with different grain size, surface treatments and aggregates, coming from some Neolithic Italian sites, exploring the potential of the LIBS method in micro-chemical studies of ancient potsherds

Coupling of electron and vibrational spectroscopy with false colour imaging for the investigation of natural dyes in historical fabrics (15th-18th centuries)

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Multivariate calibration in Laser-Induced Breakdown Spectroscopy quantitative analysis: The dangers of a ‘black box’ approach and how to avoid them

The introduction of multivariate calibration curve approach in Laser-Induced Breakdown Spectroscopy (LIBS) quantitative analysis has led to a general improvement of the LIBS analytical performances, since a multivariate approach allows to exploit the redundancy of elemental information that are typically present in a LIBS spectrum. Software packages implementing multivariate methods are available in the most diffused commercial and open source analytical programs; in most of the cases, the multivariate algorithms are robust against noise and operate in unsupervised mode. The reverse of the coin of the availability and ease of use of such packages is the (perceived) difficulty in assessing the reliability of the results obtained which often leads to the consideration of the multivariate algorithms as ‘black boxes’ whose inner mechanism is supposed to remain hidden to the user. In this paper, we will discuss the dangers of a ‘black box’ approach in LIBS multivariate analysis, and will discuss how to overcome them using the chemical-physical knowledge that is at the base of any LIBS quantitative analysis

Spectroscopic techniques applied to the study of Italian painted Neolithic Potteries

In the field of cultural heritage, the study of the materials used by the artist is useful both for the knowledge of the artwork and for conservation and restoring interventions. In this communication, we present results of some decorations analysis obtained by the use of two complementary laser techniques: micro-LIBS and micro-Raman spectroscopy. With both techniques it is possible to operate in a practically nondestructive way on the artwork itself, without sampling or pretreatment. Micro-Raman spectroscopy gives information on the molecular structure of the pigments used, while micro-LIBS can give quantitative information about the elemental composition of the same materials. In this paper, qualitative results are reported obtained on the study of some Neolithic potteries coming from the archaeological site of Trasano (Matera); the fragments show decorations in different colors, red, black, and white. The aim of the study was detecting whether the colored decorations were made by using added pigments or came from the manufacturing process