Mortars and plasters - How to characterize mortar and plaster degradation

AbstractThe degradation of mortars and plasters can represent a threat for their preservation. That is why a deep understanding of the degradation mechanisms and the identification of degradation patterns is strongly recommended for who is in charge of conservation of archaeological sites and of built heritage in general. Here, it has been described what are the main degrading agents that can be detected on mortars and plasters and how they act to produce degradation. Moreover, an overview of the analyses which can be carried out directly on site and in laboratory as well has been reported. The knowledge that can be achieved by using such methods represents an essential tool to set up a suitable conservation plan. In addition, a more detailed analysis can also have a research purpose, since they can be useful to clarify some mechanisms and interactions that still remain unclear

The polychrome works “Prayer of Tobias and Sarah” and “The Archangel Raphael reveals himself to Tobi and his son Tobias”, inside the Cathedral of Cosenza: diagnostic investigations and considerations on the conditions of conservation

The oil paintings and “Prayer of Tobias and Sarah” and “The Archangel Raphael reveals himself to Tobi and his son Tobias”, executed by Francesco Bruno at the end of the XVIII century on oval Conservation Science in Cultural Heritage 210 shaped canvas, were investigated by integrated physica-chemical and analytical methodologies in order to obtain scientific data capable of elucidating the state of conservation and the painting technique. Optical (OM) and electronic (SEM-EDS) microscopy, micro-FT-IR spectroscopy, were applied on some microfragments whilst the two whole paintings were analyzed by the non invasive IR reflectografy technique. The reflectography evidenced some pentimenti of author on the canvas “Prayer of Tobias and Sarah”, while invasive analysis made it possible to locate the stratigraphic sequence of each canvas and to characterise the constituent materials

Study of alteration and degradation products of a Roman marble sarcophagus located in the medieval cloister of the old st Cosimato’s Convent, now the new "Regina Margherita Hospital” (Rome)

Optical and SEM-EDS microscopy, FT-IR and mFT-IR spectroscopy investigations have been applied to the study of alteration and degradation products of a Roman sarcophagus located in the medieval cloister of St Cosimato’s Convent, now the new “Regina Margherita Hospital” (Rome) before restoration work. This scientific analysis was performed in order to compare it with a diagnosis report based on the restorer’s expertise. The sarcophagus is small and consists of a single block of fine-grained marble covered by a thick pink patina. The results obtained from this diagnostic investigation, allow us to draw important conclusions about the state of conservation of this archaeological artefact. The main components found in the samples analyzed are: black crust, calcium oxalate, organic matter due to recent conservation treatment, calcite, iron-oxides and coloured earths. In particular, the combined used of petrographical and mFT-IR analysis provided useful insights into the polishing and consolidation processes of archaeological artefacts

New insights to assess the consolidation of stone materials used in built heritage: the case study of ancient graffiti (Tituli Picti) in the archaeological site of Pompeii

Abstract Tituli Picti are an ancient form of urban graffiti very common in the archaeological site of Pompeii (Naples, South—Italy). They are generally made of red pigments applied on walls of Campanian ignimbrite. This paper deals with a scientific investigation aimed to their conservation. This is a challenging task since it requires a multidisciplinary approach that includes restorers, archaeologists and conservation scientists. The study has provided suggestions on the proper way to conserve Tituli Picti over time. In the present work, several specimens of Campanian ignimbrite were painted with red earth pigment; lime and Arabic gum have been used as binders as well. Such painted stones were treated with three consolidants: a suspension of reactive nanoparticles of silica, ethyl silicate and an acrylic microemulsion. Treated and untreated specimens were subjected to thermal aging, artificial solar radiation and induced crystallization decay. It has been assessed the colorimetric variations induced by treatments. Moreover, the micromorphologic features of the consolidated surfaces have been highlighted by means of electron microscope observations. The scotch tape test allowed to compare the superficial cohesion induced by the three used products. According to the results, ethyl silicate seems to represent the most successful product

Indagini diagnostiche finalizzate alla caratterizzazione dei materiali costitutivi e dei prodotti di degrado di beni monumentali: alcuni casi studio e formulazione di nuovi prodotti per la loro conservazione

Dottorato di Ricerca in Scienze della Terra, XXIII Ciclo, a.a. 2009Università della Calabri

Protection of Urban Art Painting: A Laboratory Study

Urban art is a form of artistic visual expression and communication that is created in the street and generally in the public dimension of urban spaces. Often these kinds of artworks are in outdoor environments, and they usually suffer from atmospheric weathering and anthropic vandalism. Recently, several strategies have been used to limit or remove the effects of such vandalism. Currently, the use of quartz paints is growing among artists; such paints after setting are more porous and rough on the surface with respect to regular paints. The aim of the study is to assess the performance of anti-graffiti coatings on quartz artworks paints. Two anti-graffiti products were chosen, and their behaviors were assessed in the laboratory by means of contact angle measurement, water capillary test, colorimetric analysis, and optical and electron microscopy. Results showed good water repellence efficacy of the tested products, demonstrating that they are suitable for the protection of urban art, but at least two applications on the surface are needed to achieve good performance

Hyperspectral Survey Method to Detect the Titanium Dioxide Percentage in the Coatings Applied to the Cultural Heritage

Nanotechnologies provide new materials for the consolidation and protection of the Cultural Heritage: innovative solutions are represented by ethyl silicate or silica nanoparticles dispersed in aqueous colloidal suspensions mixed to titanium dioxide in nanometric form. The challenge of this work is to provide a quick and non-invasive survey method able to evaluate the titanium dioxide amount in the coatings applied on the treated stones. In fact, the titanium dioxide weight percentage incorporate into the coating depends on both application phase and, over time, environmental biological and chemical conditions. In this paper, we show the preliminary results obtained by spectroradiometric survey carried out on marble samples coated through nanoparticle films. The coatings were prepared increasing weight percentage of the titanium dioxide from 0 w% to 8 w%. The data obtained through a field hyperspectral sensors shown spectral signatures depending on the content of titanium dioxide. In fact, the samples are characterized by different spectral shapes in the wavelength range 350–400 nm, especially. The results are useful to develop a procedure for checking the application phase of coatings on the tangible Cultural Heritage. Moreover, the same method can be used, also, both to analyze the effect of the nanoparticle product on the base stone, before its application, and to verify the efficiency of the coating, over time

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

Detection of the TiO2 Concentration in the Protective Coatings for the Cultural Heritage by Means of Hyperspectral Data

Nanotechnology-based materials are currently being tested in the protection of cultural heritage: ethyl silicate or silica nanoparticles dispersed in aqueous colloidal suspensions mixed with titanium dioxide are used as a coating for stone materials. These coatings can play a key role against the degradation of stone materials, due to the deposit of organic matter and other contaminants on the substrate, a phenomenon that produces a greater risk for the monuments in urban areas because of the increasing atmospheric pollution. However, during the application phase, it is important to evaluate the amount of titanium dioxide in the coatings on the substrate, as it can produce a coverage effect on the asset. In this work, we present the hyperspectral data obtained through a field spectroradiometer on samples of different stone materials, which have been prepared in laboratory with an increasing weight percentage of titanium dioxide from 0 to 8 wt%. The data showed spectral signatures dependent on the content of titanium dioxide in the wavelength range 350–400 nm. Afterwards, blind tests were performed on other samples in order to evaluate the reliability of these measurements in detecting the unknown weight percentage of titanium dioxide. Moreover, an investigation was also performed on a test application of nanoparticle coatings on a stone statue located in a coastal town in Calabria (southern Italy). The results showed that the surveys can be useful for verifying the phase of application of the coating on cultural heritage structures; however, they could also be used to check the state of the coated stone directly exposed over time to atmospheric, biological and chemical agents