Franca Persia

Air pollution loads on historical monuments: an air quality model application to the marble Arch of Titus in Rome

Abstract Atmospheric pollution is one of the reasons for stone weathering of monumental structures; at the same time old town centres are high concentration areas of pollutant sources (traffic and domestic heating) and of outdoor works of art. The use of air dispersion models represents a short means of answering many questions concerning pollution and it is a complementary way to the traditional ad hoc measurement of pollutant concentrations. An application of DIMULA, an analytical multisource dispersion model, and of CALINE 3, an air dispersion model specially developed for pollutant line sources (road links) will be described. The first was applied to the entire urban area of Rome and the second to the surroundings of the Arch of Titus. A simulation was performed relative to the period of in situ monitoring of air pollutant species and meteorological conditions. Moreover simulations of the effect of possible actions to reduce pollution around the monument (e.g., traffic limitation, use of different fuels) have been performed. Once the model has been validated, this approach, compared with the traditional approach involving a large amount of measurements, has the merits of being reliable and economical.

Development of nanocomposites for conservation of artistic stones

Properties of consolidant and protective materials modified with nanoparticles were analysed in this study following their application onto marble samples. For this purpose, different solutions of an acrylic resin with dispersed SiO2 and TiO2 nanoparticles were prepared. The relative durability of Paraloid B72, an acrylic resin used as consolidant and modified by nanoparticles, was evaluated comparatively by means of diverse diagnostic techniques, namely, scanning electron microscopy, laser-induced fluorescence, ultrasonic sound, colorimetry, total immersion water absorption and contact angle. The results demonstrate that nanoparticles enhance the effectiveness of consolidant and protective material because they induce substantial changes of surface morphology of the coating layer.

Crime art on the stone: graffiti vandalism on cultural heritage and the anti-graffiti role in its surfaces protection

Apparently perceived like an easy thing commonly used, spray paint is a very complex product composed by substances strongly penetrating particularly into the porous materials. This characteristic is very hazardous for our cultural heritage. The problem concerning the surfaces protection from paints and signs is very hard to solve, both for the difficulty to remove these substances and for the variety of the materials that react in a different manner to the various paints and cleaning treatments because of their different physical-chemical characteristics. With the aim to evaluate the damages originated by the spray paints on the stones and the efficacy of anti-graffiti products, some laboratory tests have been carried out. Two different limestones have been selected like supports: a little porous, polishable wakestone and a very porous bio-calcarenite with very scarce mechanical properties. Both these limestones are used as coverings and structural elements of buildings and monuments around Mediterranean basin. Concerning the spray paint cans, the most popular Montana mtn94 has been used, and two commercial anti-graffiti have been applied as protective products. Using Scanning Electron Microscope, Infrared Spectrometry, Colorimetry, Mercury Intrusion Porosimetry and Contact Angle Analysis the interactions stone-paint, stone-anti-graffiti and paint-anti-graffiti have been investigated. In order to evaluate the real efficacy of the anti-graffiti, some cleaning and removal paint tests have been carried out. The research highlights that the anti-graffiti cause variations concerns the colour and/or the wettability in both limestones. Their effects are strictly related to the stonework and their microstructure but also the interaction with the paint is influent too.

Performance of nanocomposites for preservation of artistic stones

In this work, the effectiveness of nanocomposite surface treatments as protective systems for artistic stones was evaluated. Pyrolitic silica and titania nanoparticles were dispersed in a commercial silicon-based polymer and applied on marble and travertine samples. Artificial aging processes, both in climatic chamber and in solar box, were carried out to simulate real degradation processes in terms of photo-thermal effects and physical-chemical damage. The performances of the nanocomposites used as consolidant were evaluated comparatively by means of diverse diagnostic techniques, namely: scanning electron microscopy (SEM), laser induced fluorescence (LIF), ultrasonic technique, colorimetry, total immersion water absorption and contact angle. The results show that some properties of conservation materials can be improved by the presences of nanoparticles because they induce substantial changes of surface morphology of the coating layer and counter the physical damage observed during artificial weathering.

Laser-based techniques for a multidisciplinary action aimed at the restitutive restoration of S. Costanzo church in Ronciglione (Italy)

In the framework of the COBRA (Conservation of Cultural Heritage through Radiation and Enabling Technologies) project a multidisciplinary study was carried out in order to restore the mural painting of the dome of the S. Costanzo church in Ronciglione (Italy). Large difficulties were met during the restitutive restoration of the original renaissance fresco decorating the dome, patronized by the Italian Ministry of Cultural Heritage (SABAP RM MET). In fact, two and sometimes three layers of paint, which lays on an extremely crumbled substrate were detected on the surface, in addition to large, deep and complex degradation forms with the presence of efflorescence. To solve such a critical situation, researchers, conservators and laser cleaning system suppliers collaborated to plan the most appropriate intervention. Laser-based diagnostics were employed to characterize different areas of the fresco surface before and after cleaning tests. In particular, ENEA offered its prototypes of LIF (Laser Induced Fluorescence) and RGB-ITR (Red Green Blue Imaging Topological Radar, an innovative 3D colour laser scanner) in addition to a laser Raman system and an infrared camera for thermographic measurements for both the material and degradation recognition and a micro-structural study. The results obtained allowed pointing at the most suitable restoration and conservation strategies. The cleaning tests were performed with both classical methods and lasers made available by El.En. group. Different operative parameters such as pulse duration, repetition rate, energy were tested. The laser employed made it possible to overpass the difficulties encountered by other cleaning techniques: degradation and painting layers were removed selectively, allowing bringing to light the original surface.

Nanomaterials for Conservation of Artistic Stones: Performance and Removal Tests by Laser Cleaning

In this work, nanomaterials were used as consolidants and protective layers for artistic stones. Synthetized nanocomposites were applied on marble and their performances as protective and water repellent coating were characterized. For the preparation of the novel nanocomposites, SiO2 and TiO2 nanoparticles were synthesized by laser pyrolysis and were dispersed in acrylic polymer and silicon-based resin. To evaluate the retreatability of water repellent treatments, the capability of laser to remove protective layers was explored. Laser cleaning tests with different working parameters have been carried out to optimize the effectiveness of the process. The effects of laser treatments on stone surfaces and on the applied nanocomposites were estimated by using confocal optical microscopy and Laser-Induced Fluorescence (LIF).