Giovanni Visco

Microclimate monitoring in the Carcer Tullianum: temporal and spatial correlation and gradients evidenced by multivariate analysis; first campaign

Too often microclimate studies in the field of cultural heritage are published without any or scarce information on sampling design, sensors (type, number, position) and instrument validation. Lacking of this fundamental information does not allow an open discussion in the scientific community. This work aims to be an invitation for a different approach.Three main parameters (temperature, humidity, luminance) were monitored in a selected part of a complex construction by an inexpensive self-assembled system along some horizontal and vertical vectors. All data was then processed and analyse by chemometric methods. Some measurements of oxygen, carbon monoxide and dioxide and pressure were also performed.Correlation of some indoor and outdoor data was shown for temperature and humidity. In case of outdoor changes the indoor environment reacted with a certain delay which is position-dependent and more evident for humidity data. The two observed rooms (Carcer and Tullianum) behave differently and the hypogean one is less influenced by the outdoor environment. Instrument validation before and after the campaign, allows to consider detected variations as significant.The fundamental importance of Sampling Design and of instrument validation before and after the monitoring campaign was enhanced. The choice of two main and two minor vectors allowed detection of different behaviour for the two rooms, also permitting to detect for both rooms a trend towards a spontaneous microclimate necessary for a conservation project. In the next campaign we will focus on the choice of the best sampling frequency to use more sophisticated statistical methods.

Characterization of black pigment used in 30 BC fresco wall paint using instrumental methods and chemometry

Background and methodsSeveral standard powdered black pigments were characterized by means of thermogravimetry TG-DTG and allied techniques. These pigments were used to make standard plaster frescoes at this purpose prepared. The latter ones were subjected to Raman and reflectance analysis. The results obtained, together with TG data, were chemometrically processed and used to identify an analogous standard fresco fabricated by an unknown commercial black pigment, obtaining excellent results.ResultsThe same colorimetric and reflectometric techniques, coupled with suitable chemometric techniques, were then successfully used to identify the type of black pigment present in an ancient roman fresco of the Imperial Age (30 B.C.).ConclusionTG-DTG resulted useful techniques to autenticate powdered black pigments.Colorimetry and Raman, but also the only colorimetry, were useful to identify an ancient black pigment in situ.

New approach to the differentiation of marble samples using thermal analysis and chemometrics in order to identify provenance

BackgroundThe possibility of applying a novel chemometric approach which could allow the differentiation of marble samples, all from different quarries located in the Mediterranean basin and frequently used in ancient times for artistic purposes, was investigated. By suggesting tentative or allowing to rule out unlikely attributions, this kind of differentiation could, indeed, be of valuable support to restorers and other professionals in the field of cultural heritage.Experimental data were obtained only using thermal analytical techniques: Thermogravimetry (TG), Derivative Thermogravimetry (DTG) and Differential Thermal Analysis (DTA).ResultsThe extraction of kinetic parameters from the curves obtained using these thermal analytical techniques allowed Activation Energy values to be evaluated together with the logarithm of the Arrhenius pre-exponential factor of the main TG-DTG process.The main data thus obtained after subsequent chemometric evaluation (using Principal Components Analysis) have already proved useful in the identification the original quarry of a small number of archaeological marble finds.ConclusionOne of the most evident advantages of the thermoanalytical – chemometric approach adopted seems to be that it allows the certain identification of an unknown find composed of a marble known to be present among the reference samples considered, that is, contained in the reference file. On the other hand with equal certainty it prevents the occurrence of erroneous or highly uncertain identification if the find being tested does not belong to the reference file considered.

Second campaign of microclimate monitoring in the carcer tullianum: temporal and spatial correlation and gradients evidenced by multivariate analysis

BackgroundThis paper discusses results obtained in the second monitoring campaign of the Carcer Tullianum, a particular hypogeum environment located in the historical centre of Rome (Italy). In the first paper we stressed the need to apply chemometric tools to this kind of studies in order to obtain full and significant information; really information on sampling design, sensors (type, number, position) and instrument validation seems to be not easy to find in literature for researches dealing with monitoring of indoor environments.Also in this case three main parameters (temperature, humidity, illuminance) were monitored in the complex construction by an inexpensive self-assembled system along some horizontal and vertical vectors together with some measurements of oxygen, carbon dioxide and barometric pressure.With respect to the first campaign, we used a higher number of sensors to cover a new excavated zone; for the same reason, as well as to take into account the presence of visitors, a different experimental design was adopted.ResultsDifferent data treatments were applied to data coming from all the used sensors. A good view of the microclimate was obtained that also resulted coherent with the different position of the three rooms constituting the monitored site (Carcer, Tullianum, Convent). Classical time plots resulted useful to evidence the correlation of the main monitored parameters (T, RH% and illuminance) with macroclimate, as well as their delay in following macroclimate. Box-Whisker and Gain-Loss graphs evidenced at the best the microclimate differences between the three rooms; an almost hypogean microclimate was evidenced for the lower room (Tullianum) where humidity values range between 90 and 100% while lower values, but anyway higher than the external, and spread more widely were measured passing to Convent and Carcer with minimum values around 50% for the last. A scarce or very scarce correlation with macroclimate was evidenced for all the three main measured parameters. Lighting results mainly dependent on artificial light and only in few cases, but unfortunately in the most precious zone, illuminance exceeds values suggested by Normative.ConclusionsBox-Whisker and Gain-Loss graphs allowed us to have the best view of the microclimate for all the monitored rooms. The influence of lighting by lamps on the other monitored parameters resulted overlapped and clearly topped the solar one. The worst situation was found in the Carcer, where the presence of the main chandelier worsens the state of the frescoed walls, already subjected to wide changes in temperature and humidity. Also the lighthouse located above the Convent provokes lighting exceeding values suggested by Normative while, as expected, LEDs resulted as suitable source of light from a conservation point of view.Susanne Heidi Plattner, Patrizia Fortini and Maria Pia Sammartino contributed equally to this work

Development of a new sensor for total organic carbon (TOC) determination

A sensor to determine TOC is described. It is based on the photoassisted degradation of organic compounds concurring to TOC and on the determination of the resultant CO2. The sensor was successfully tested on target molecules, demonstrating that the linear correlation constant between TOC values and produced CO2 varies according to the considered compound so that absolute value determination is not possible in largely heterogeneous solutions but can only be referred to reference compounds on the TOC scale.

Correction of the interference by mixing the reagents in the bioluminescent determination of ATP in environmental samples by an interfaced PC photometer and a robust regression procedure

Abstract An automated procedure for correcting the interference due to mixing the reagents in the determination of ATP by a bioluminescent technique is described. The measurements were performed by an in-house interfaced PC photometer. An automated procedure based on a robust regression method and outliers detection was applied to exclude the time of the mixing of the reagents from the global time of reaction. In fact the mixing of the reagents is responsible of the poor analytical precision (RSD%>25) and low sensitivity (limit of detection≈2×10-8 mol/l). By this procedure, the precision (RSD%<7) and sensitivity (limit of detection≈8×10-10 mol/l) were improved. The method was applied to the determination of ATP in marine sediments and good recovery within 90–108% was obtained. For non-polluted samples the measurement can be carried out by direct comparison with standard solutions. The standard addition procedure is recommended for polluted samples.

Rings or daggers, axes or fibulae have a different composition? A multivariate study on Central Italy bronzes from eneolithic to early iron age

AbstractBackgroundOne of the main concerns for archaeo-metallurgists and archaeologists is to determine to what extent ancient craftsmen understood the effect of metal alloy composition and were able to control it in order to produce objects with the most suitable features.This problem can be investigated by combining compositional analyses of a high number of ancient artefacts with correlation analyses of the objects’ age, production site, destination of usage etc. – and thus chemometric data treatment is carried out. In this study, multivariate analyses were performed on a matrix composed of elemental compositional data from 134 archaeological bronze objects, obtained by XRF analyses. Analysed objects have been dated back from the Eneolithic Period to the end of the Bronze Age including the early Iron Age and were excavated in Central Italy (mainly Abruzzo Region).ResultsChemometric analysis was performed attempting to visualise clouds of objects through PCA. In parallel and independently, object grouping was attempted using several different approaches, based on object characteristics (e.g. shape, weight, type of use – cutting or hitting and age) following indications given by archaeologists (or derived from the archaeological context).Furthermore, case-tailored data pretreatment (logratio-centred scaling) was used, but no homogeneous groups could be identified.ConclusionsBy using chemometric data analysis, homogeneous groups of objects could not be detected, meaning that compositional data of alloys is not correlated with the considered objects’ characteristics. This favours the conclusion that – without discussing the ascertained ability of ancient foundry-men - they had also already discovered the convenience of recycling broken objects thus producing a more or less similar bronze alloy each time, depending on materials’ availability; necessary mechanical characteristics could then be obtained by post processing. Graphical AbstractScores PCA plot in 3D space with 3 different bronze objects.

A multidisciplinary diagnostic approach preliminary to the restoration of the country church “San Maurizio” located in Ittiri (SS), Italy

BackgroundThe knowledge of the structure of an artefact, as well as that of its constituent materials and of the hosting environment surely ensures safe guideline for its restoration. Unfortunately, in most cases, a scientific investigation preliminary to restoration is not accomplished due to its high costs and, as a fact, diagnostics is performed only for very precious artworks.This paper aims to provide a multidisciplinary diagnostic procedure that, although not exhaustive, is rigorous and relatively low cost. It was employed in view of the restoration works on a country church located in Sardinia. A careful inspection of all the architectural elements was carried out in order to highlight structural damages as well as sources of them. One stone and one plaster samples were analysed. The salt content was determined, in two different areas of the church, using three different sampling procedures while only the normed method was used for the determination along the stratigraphy of the sampled plaster. Microclimate monitoring was also carried out.ResultsWater infiltration through the roof was observed. Natural stones and artificial building materials used in the basic architecture resulted to have local source. Both the preliminary “by eye” inspection and the optical microscopy revealed several finishing layers in the investigated plaster samples. The salt content, with some exception, resulted rather low. Microclimate parameters show significant variations only in few areas of the building.ConclusionsDamage observed inside the oldest part of the Church seems to be mainly related to water infiltrations through the roof and the lack of an effective drainage of the rainwater due to a previous bad restoration. Masonry from one of the newest rooms, showing a strong biodeterioration, as well as some areas inside the nave, revealed a significantly high sulphate content. Building materials (stone and aggregates of mortars) are of local provenance.

Proposal of a new analytical procedure for the measurement of water absorption by stone. Preliminary study for an alternative to the Italian technical normative NORMAL 07-81

BackgroundItalian technical normative in the field of cultural heritage is often considered insufficient or not suitable in practise, therefore efforts are necessary to design new and/or improve already existing ones.ResultsIn this paper an alternative analytical procedure for the determination of water absorption (by full immersion) by stone material, described in the NORMAL 07-81 document, is proposed. Improvements concern methods accuracy and reduction of sample size; further also density data is obtained.ConclusionsThe new procedure was applied on three different marble samples and outcomes are encouraging, but further testing is running to better understand to what extent sample size can be reduced without worsening accuracy of results, taking into account that stone is a very heterogeneous material.

A multivariate approach for a comparison of big data matrices. Case study: thermo-hygrometric monitoring inside the Carcer Tullianum (Rome) in the absence and in the presence of visitors

In the last decades, the very fast improvement of the analytical instrumentation has led to the possibility of quickly and easily getting a lot of data; in turn, the need of advanced statistical methods suitable to extract the full information furnished by instruments has increased. Such kind of data treatments is particularly important in any case of continuous monitoring of one or more parameters, so the microclimate monitoring is a typical example for this application. Microclimate control is essential in the conservation of Cultural Heritage (CH), but decisions on optimal conservation parameters cannot base only on existing norms that do not take into account the environment’s history. Often CH has survived for many centuries in conditions that must be considered risky but also a stable state (equilibrium) resulting from a long adaptation process during which a more or less heavy damage occurred to the materials. Any successive change of microclimate parameters has interrupted this equilibrium conditions and has induced further damage to material until a new equilibrium is reached; dimension and frequency of changes are proportional to the expected damage. This thermodynamic consideration provides the background for a CH conservation project based on microclimate control and highlights the importance of environmental monitoring for the identification of equilibrium parameters to be maintained. In 2010, we monitored the microclimate of an important historical building in Rome, the Mamertino Carcer, before its opening to visitors. One year later, we repeated the monitoring in the presence of visitors, and here, we present a careful choice of multivariate data treatments adopted for an enough, simple and immediate evaluation of the microclimatic changes; this allows an easier understanding also for persons with not too deep scientific background, such as Superintendents and, in turn, really useful information to provide suggestions for a conservation project. Results evidenced the expected loss of isolation of the site that occurred by opening to visitors; this led to wider excursions of both temperature and relative humidity and, in turn, to a worsening of the conservative conditions. Surely, a monitoring of particulate matter, correlated to air fluxes and, in turn, to microclimate, is of fundamental importance for the conservation of frescoes and will be object of one of our future diagnostic interventions in the site.