Papers by Francesca Becherini
Background and methods: Wall paintings and architectural surfaces in outdoor environments are exp... more Background and methods: Wall paintings and architectural surfaces in outdoor environments are exposed to several physical, chemical and biological agents, hence they are often treated with different products to prevent or slow down their deterioration. Among the factors that have to be taken into account in the selection of the most suitable treatment for decorated surfaces, the aesthetic compatibility with the substrate is of great importance in the cultural heritage field; minimizing colour variation after treatment application is a crucial issue in particular for painted surfaces.
In the framework of the European Project Nanomatch the color variation induced on wall painting mock-ups by the two innovative consolidants (calcium alkoxides) developed was evaluated using colorimetry in comparison with two traditional products. In this work these innovative consolidants have been also tested in combination with two commercial biocides and the results of colorimetric measurements discussed. Moreover, as the univariate approach didn’t allow to draw clear conclusions on the relation between the different sources of data variability, multivariate analysis was performed on colorimetric data.
Results: Principal Component Analysis (PCA) and multi-way Parallel Factor Analysis (PARAFAC) were successfully applied to colorimetric data to investigate the short-term effects of the application of different consolidants on wall painting surfaces, making it possible to study at the same time the different sources of data variability, i.e. treatments, painting techniques, pigments. Finally, a ranking list of the treatments under study in terms of colour variation induced on the surface was established, in function of the painting technique and pigment, taking also in consideration the combination consolidant/biocide. In particular, given the true multi-way nature of the data, PARAFAC model turned out to be extremely useful in the study of the dependence of colour variation on pigments, a critical issue for painted surfaces, that was not clear using univariate approach.
Conclusions: Multivariate approach to colorimetric data and especially 3-way PARAFAC method resulted a powerful technique to evaluate in short-term the color compatibility of consolidants for wall paintings, improving data interpretation and visualization, and thus outperforming the univariate statistical analysis.
The impact of lighting, heating and people in re-using historical buildings are discussed for the... more The impact of lighting, heating and people in re-using historical buildings are discussed for the case study concerning the ceremony room (i.e. the Giant Hall) of a mediaeval palace in Padova. The Hall has substantially four major problems for conservation: (i) the impact of heating, lighting and people when the room is used; (ii) many cracks on the oak panels of the coffered ceiling; (iii) the soiling by dust and soot particles deposited on the frescoes; (iv) the stained glass windows. A microclimate study was performed to know the impact of the environmental variables, and the use of the room, on the artworks preserved inside. The study has proved the impact of the lamps (both incandescence and compact fluorescent lamps) on the ceiling, the penetration of external air in the room, the heat and the moisture released by people, the impact of sunshine through windows and the scatter diagram of the daily cycles in temperature (T) and relative humidity (RH). During winter concerts, the strips of lead which are wrapped round the edge of the cut glass pieces in stained glass windows easily drop below the dew point and form condensation, starting corrosion. A discussion concerns the allowed variability, which should not exceed risk thresholds. A safe interval can be established within the area determined by the most frequent T and RH natural cycles. In fact, both of the cycles were compatible with the artefacts, or the artefacts were already damaged to allow the exceeding dimensional changes. Attention should be paid in the variability external to this area, especially approaching or exceeding a limit equal to twice the mode of the natural variability.
The multidisciplinary EC VIDRIO project has the purpose of providing a better understanding of th... more The multidisciplinary EC VIDRIO project has the purpose of providing a better understanding of the effect of the environment on glass surfaces and paint (grisaille) and to evaluate the efficiency of the protective glazing system, in order to find sustainable solutions to protect ancient stained glass windows from the main causes of glass weathering, in particular the condensation phenomenon. Hence, a new device, named " dew point sensor " , was built and patented to protect the stained glass windows by detecting the condensation on the glass surface. The research was focused on laboratory tests and experimental campaigns: two important French monuments, Sainte-Chapelle in Paris and Saint-Urbain Basilica in Troyes, were monitored, while the study in Cologne Cathedral (Germany) is still in progress. Three different systems were used to detect the phenomenon of condensation in order to evaluate and compare their accuracy and reliability: the indirect measurement through mathematic calculations using air temperature and relative humidity, and two direct measurements by means of the dew point and the leaf wetness sensors. The laboratory tests and research in the field made evident the errors associated with the measurements of the condensation process, and the accuracy and reliability of the new device. The efficiency of the protective glazing system, as regards to the weathering of the stained glass windows, has been confirmed. In fact, the presence of a protective glazing reduces the danger of condensation on the internal side of the ancient window and also the total time of the high relative humidity values of the air in contact with the protected window.
Science of The Total Environment, 2010
An example of an integrated approach to assess air pollution threats to cultural heritage in a se... more An example of an integrated approach to assess air pollution threats to cultural heritage in a semi-confined environment is presented in this work, where the monitoring campaign carried out at the Michelozzo's Courtyard (in Palazzo Vecchio, Florence, Italy) is used as a case study. A wide research project was carried out, with the main aim of obtaining the first quantitative data on air quality and microclimate conditions inside the Courtyard, and, if possible, identifying the main causes of degradation and suggesting appropriate conservation strategies. The investigation adopted a holistic approach involving thermographic measurements on the wall paintings, microclimatic analysis, gaseous pollutant monitoring, atmospheric particles characterisation and dry deposition compositional analysis. Attention was focused on the wall painting depicting the city of Hall because of its anomalous and critical conservation conditions, which are visible at a glance, due to the contrast between a wide darker zone around the central subject of the painting and external lighter areas.
A microclimatic monitoring of the Longobard Temple in Cividale del Friuli, Udine (Italy), was per... more A microclimatic monitoring of the Longobard Temple in Cividale del Friuli, Udine (Italy), was performed between 2011 and 2012 aimed at investigating the causes of the different damage features observed in the stucco statues located in the opposite sides of west-southwest wall. The thermo-hygrometric conditions of the air close to the statues were continuously monitored for one year and the surface temperature of the statues was investigated by means of thermography. According to the results, no remarkable differences in the current microclimatic conditions measured at the two sides of the west-southwest wall were found, hence the cause of the different state of conservation of the statues has to be ascribed to phenomena occurred in the past. Nevertheless, the thermo-hygrometric values measured close to the statues are not fully in compliance with respect to the ranges indicated in literature for the conservation of the stucco ornaments.
When historic buildings and monuments are located in urban environments their exposure to signifi... more When historic buildings and monuments are located in urban environments their exposure to significant harmful deterioration caused by different pollutants is inevitable. Industrial, civil and transport emissions produce the so-called multi-pollutants which constitute a major danger for cultural heritage because of the corrosion and blackening phenomena they cause. It has been predicted that the chemical composition of the atmosphere will change and this will lead to new damage processes which will affect surfaces and materials of the historic objects. In this scenario, TeACH aims to identify the major critical pollutants and the best solutions to investigate the changing degradation processes, developing new instruments for monitoring and deliver guidelines for a sustainable protection of the cultural heritage. The project focuses on the immovable heritage, at the same time studying the effects on indoor movable heritage from a multidisciplinary point of view. The main objectives of the project can be summarized as follows: to identify multi-pollutants which have a changing impact on the cultural heritage and prioritize the most important ones; to develop new devices and tools and provide a compact and economical kit of instruments for monitoring the outdoor environment and to develop a tool to forecast damage; to perform field tests in six urban localities in Europe and the Mediterranean area, with different climate and environmental conditions; to deliver guidelines for the future prioritization of air pollution monitoring for a sustainable protection of cultural heritage; and to disseminate the project results. TeACH will deliver new and improved non-destructive technologies for the overall damage assessment, diagnosis and monitoring of cultural heritage. The final users of the project results will be architects and restorers, conservators and cultural heritage professionals, public institutes for conservation; policy-makers and curators.
The available scenarios of pollutant trends in Europe indicate that the effect of industrial, dom... more The available scenarios of pollutant trends in Europe indicate that the effect of industrial, domestic and transport emissions on corrosion and soiling will continue to constitute a serious threat to Cultural Heritage. Such effects require improved methods for a more accurate diagnosis, monitoring and assessment of the damage. Within this framework, the monitoring methodology applied within the European project TeACH (Technologies and tools to prioritize assessment and diagnosis of air pollution impact on immovable and movable cultural heritage) (2008-2012) allows to assess the impact of the main pollutants on historic buildings. As a part of this approach, a new kit able to monitor the environmental parameters critical for the conservation of architectural surfaces and to evaluate the related damage in terms of surface color change was developed. The monitoring methodology described in the present paper has valuable application potential in the definition of preventive conservation strategies for a wide range of heritage assets.
Climate and environmental parameters are directly or indirectly involved in almost all decay proc... more Climate and environmental parameters are directly or indirectly involved in almost all decay processes for outdoor cultural heritage. In this context, climate change is believed to play a driving role in diversifying future damage processes and efforts have focused on the prediction of the impact of climate change on damage effects on stone materials [1-4]. Therefore, consolidating and protective agents are often needed to reduce the effects of the environment on original substrates. Among inorganic consolidants, nanostructured materials have been largely studied and successfully used according to criteria of stability and high compatibility with the inorganic matrices [5-8] although data still lacks regarding their durability in outdoor conditions. The European Project NANOMATCH is focused on the development of innovative and durable inorganic nanomaterials for the consolidation and protection of Cultural Heritage substrates. An alkaline earth alkoxide as precursor of calcium carbonate has been synthesized as stone consolidating agent, being capable to penetrate the porous substrate and to form a calcium carbonate coating on the pore walls. Efficacy, compatibility and durability are the three main goals to be achieved by the innovative consolidating agent developed within the project. After the identification of the most suitable synthetic route to produce the metal-alkoxides, a final formulation for stone treatment has been set up for the application on carbonate stones. Representative carbonate building stones from different European countries and historical substrates characterized by ongoing damage processes have been selected to be treated and then exposed to outdoor conditions in four different European sites (Tab. 1) in order to test efficacy, compatibility towards substrates and durability against climate attack of the innovative consolidating agents. Rain, relative humidity, temperature, wind and solar radiation have been prioritized among climate parameters for establishing methodologies aimed at assessing the long-term behaviour of treatments. Moreover, specific pre-treatments aimed at simulating deterioration on Carrara marble specimens as well as on Savonnières limestone ones have been carried out (Tab.1). The scheme of exposure is illustrated in Fig.1. Furthermore, microclimatic stations have been installed nearby the rack hosting stone samples. The performance of the newly developed product is evaluated by comparing results obtained: (i) before exposition, (ii) after six month and (iii) after one year of exposure by means of Optical Microscopy, Scanning Electron Microscopy, Mercury Intrusion Porosimetry, Spectrophotometry (color measurements), Scotch Tape Test and Capillarity water absorption
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Papers by Francesca Becherini
In the framework of the European Project Nanomatch the color variation induced on wall painting mock-ups by the two innovative consolidants (calcium alkoxides) developed was evaluated using colorimetry in comparison with two traditional products. In this work these innovative consolidants have been also tested in combination with two commercial biocides and the results of colorimetric measurements discussed. Moreover, as the univariate approach didn’t allow to draw clear conclusions on the relation between the different sources of data variability, multivariate analysis was performed on colorimetric data.
Results: Principal Component Analysis (PCA) and multi-way Parallel Factor Analysis (PARAFAC) were successfully applied to colorimetric data to investigate the short-term effects of the application of different consolidants on wall painting surfaces, making it possible to study at the same time the different sources of data variability, i.e. treatments, painting techniques, pigments. Finally, a ranking list of the treatments under study in terms of colour variation induced on the surface was established, in function of the painting technique and pigment, taking also in consideration the combination consolidant/biocide. In particular, given the true multi-way nature of the data, PARAFAC model turned out to be extremely useful in the study of the dependence of colour variation on pigments, a critical issue for painted surfaces, that was not clear using univariate approach.
Conclusions: Multivariate approach to colorimetric data and especially 3-way PARAFAC method resulted a powerful technique to evaluate in short-term the color compatibility of consolidants for wall paintings, improving data interpretation and visualization, and thus outperforming the univariate statistical analysis.
In the framework of the European Project Nanomatch the color variation induced on wall painting mock-ups by the two innovative consolidants (calcium alkoxides) developed was evaluated using colorimetry in comparison with two traditional products. In this work these innovative consolidants have been also tested in combination with two commercial biocides and the results of colorimetric measurements discussed. Moreover, as the univariate approach didn’t allow to draw clear conclusions on the relation between the different sources of data variability, multivariate analysis was performed on colorimetric data.
Results: Principal Component Analysis (PCA) and multi-way Parallel Factor Analysis (PARAFAC) were successfully applied to colorimetric data to investigate the short-term effects of the application of different consolidants on wall painting surfaces, making it possible to study at the same time the different sources of data variability, i.e. treatments, painting techniques, pigments. Finally, a ranking list of the treatments under study in terms of colour variation induced on the surface was established, in function of the painting technique and pigment, taking also in consideration the combination consolidant/biocide. In particular, given the true multi-way nature of the data, PARAFAC model turned out to be extremely useful in the study of the dependence of colour variation on pigments, a critical issue for painted surfaces, that was not clear using univariate approach.
Conclusions: Multivariate approach to colorimetric data and especially 3-way PARAFAC method resulted a powerful technique to evaluate in short-term the color compatibility of consolidants for wall paintings, improving data interpretation and visualization, and thus outperforming the univariate statistical analysis.