Francesca Becherini

Innovative consolidating products for stone materials: field exposure tests as a valid approach for assessing durability

The impact of climate on cultural heritage surfaces leads to several damage processes and the protection and the preservation of works of art is a challenge for conservation scientists and restorers. Traditional and innovative products are used in consolidating treatments in order to reduce the effects of the interaction environment-materials. The EC NANOMATCH Project aims at the development of innovative consolidating agents for carbonate matrices, wood and glass whose features should result in high compatibility, efficiency and long-lasting effect. In this project, metal alkoxides, molecular precursors for the deposition of metal carbonate are synthesized, characterized, tested and proposed as an alternative to traditional consolidating agents as well as to calcium hydroxide nanoparticles. This paper gives an overall description of the methodological approach adopted for the in field evaluation of durability taking into account the environmental impact. Preliminary results of the analyses carried out on carbonate stones aimed at investigating the features of the consolidating treatment are here presented and discussed.

A methodology to monitor the pollution impact on historic buildings surfaces: the TeACH project

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.

Conservation of Stained Glass Windows: An Innovative User-Friendly Portable Device Coming from the EU-VIDRIO Project

An innovative, cost-effective, user-friendly and portable device (dew sensor) to directly detect condensation on glass surfaces was developed within the EC-VIDRIO project (contract No. EVK4-CT-2001-00045), aimed at finding sustainable solutions to preserve ancient stained glass windows. The results of the research showed that the direct survey of condensation with the new sensor is more accurate and reliable than the traditional indirect microclimatic measurements. Since the construction of the first prototype, the dew sensor was developed further, continuously improved, validated in the laboratory and applied successfully on different surfaces at sites of interest in the field of Cultural Heritage; on the stained glass windows in the Saint Urbain Basilica of Troyes (France), Sainte Chapelle of Paris (France) and Cologne Cathedral (Germany); on stone walls in Petrarcas Tomb (Padua, Italy) and the Hagar Qim Temple (Malta). Now the sensor is being used in the Lascaux Caves (France). The newly built device was patented (PTC/EP2005/050665) and gave such interesting results that the Italian Ministry of University and Research financially supported a spin-off project that has lead to the creation of a new company (R.E.D. s.r.l.) in order to develop the prototype further and to produce the sensor at industrial scale.

Thermal Stress as a Possible Cause of Paintwork Loss in Medieval Stained Glass Windows

Abstract One of the main causes of the loss of paintwork from medieval stained glass windows is the propagation of cracks in the grisaille and in the underlying glass, which cannot be considered the result of a stabilization process, but the evidence of an ongoing stress. The thermal behaviour of different-coloured painted glass pieces exposed to direct solar radiation was investigated in order to study the effect of thermal stresses on the conservation of the paintwork. Experimental results have been compared with laboratory tests as well as with measurements carried out on original stained glass windows. The grisaille showed a thermal behaviour similar to that of the glass on which it is fired. A clear correlation was found between the glass thermal cycles, the increase in stress at the glass–grisaille interface and the growth of cracks in the grisaille. According to these results, protective glazing aids the preservation of the paintwork from the risk of damage and loss, reducing the thermal stresses on the glass of the stained glass windows in terms of amplitude and frequency.

A critical analysis of one standard and five methods to monitor surface wetness and time-of-wetness

Surface wetness is a synergistic factor to determine atmospheric corrosion, monument weathering, mould growth, sick buildings, etc. However, its detection and monitoring are neither easy nor homogeneous, for a number of factors that may affect readings. Various types of methods and sensors, either commercial or prototypes built in the lab, have been investigated and compared, i.e. the international standard ISO 9223 to evaluate corrosivity after wetness and time-of-wetness; indirect evaluation of wetness, based on the dew point calculated after the output of temperature and relative humidity sensors and direct measurements by means of capacitive wetness sensors, safety sensors, rain sensors (also known as leaf wetness sensors), infrared reflection sensors and fibre optic sensors. A comparison between the different methods is presented, specifying physical principles, forms of wetting to which they are respondent (i.e. condensation, ice melting, splashing drops, percolation and capillary rise), critical factors, use and cost.

Aesthetic compatibility assessment of consolidants for wall paintings by means of multivariate analysis of colorimetric data

Background and methodsWall 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.ResultsPrincipal Component Analysis 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.ConclusionsMultivariate 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.

Heart of darkness: an interdisciplinary investigation of the urban anthropic deposits of the Baptistery of Padua (Italy)

Archeological excavations beside the Baptistery of the Dome of Padua (north-eastern Italy) unearthed anthropic deposits formed between the seventh- and tenth-century ad. These were analyzed using soil micromorphology, soil chemical analyses (especially aimed at the definition of organic matter properties and dynamics), and GC/MS analyses of fecal biomarkers, the latter corroborated by principal component analysis. This inter-disciplinary study allowed differentiating between units resulting from in situ accumulation of trampled domestic waste and other, more frequent, units derived from repeated dumping or backfilling episodes. Fast accumulation of organic-rich domestic waste, coupled with an incomplete evolution of organic molecules appears as a fundamental formation process of these anthropic deposits. The overall level of fecal contamination in the Padua Baptistery sediments proved to be very low or absent.