New calcium alkoxides for consolidation of carbonate rocks. Influence of precursors' characteristics on morphology, crystalline phase and consolidation effects

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Study of Calcium Ethoxide as a New Product for Conservation of Historical Limestone

The combination of multiple physical, chemical and biological factors causes the weathering of limestone used in the field of cultural heritage. To overcome the limitations of traditional consolidating products and to meet the requirements of the historical building substrates, during the European collaborative project NANOMATCH, alkaline earth alkoxides were developed and studied as consolidating agents for limestone. Among these new products, calcium ethoxide, with the formula Ca(OEt)2, was chosen for this study and investigated in depth as an alternative consolidating treatment. It was first characterized through a study of the carbonation process: its kinetics, reaction pathway and the evaluation of formed mineralogical phases. Subsequently, it was applied on limestones with different total open porosity to test its performance as a consolidating agent. The compatibility and the efficiency of the treatment were investigated with a multi-technique approach and compared with results obtained with a reference product, based on nanolime. This study indicates that calcium ethoxide shows better results with respect to the reference product, both in terms of compatibility and consolidation effect

Portrait of an artist at work: exploring Max Ernst's surrealist techniques

AbstractMax Ernst was one of the most influential artists associated with both the Dada and Surrealist movements. However, until now, only few scientific studies have been devoted to his works. This paper presents the results of a multi-analytical investigation on six oil paintings, made between 1927 and 1942, belonging to the Peggy Guggenheim Collection in Venice (Solomon R. Guggenheim Foundation, New York). Through a combined art historical and scientific approach, this study aims at understanding Ernst's painting techniques, including frottage, grattage, dripping, and decalcomania, the used materials, and the state of conservation of the artworks. Non-invasive in situ investigations were performed by means of Vis–NIR multi-spectral imaging, X-ray fluorescence, external reflection FTIR and Raman spectroscopy. Imaging analysis revealed important information about Ernst's painting methods while the other techniques provided useful information about the ground layer, the painting materials and the presence of alteration products. Ernst's palette discloses great freedom in his use of materials and evolution during the time. This investigation demonstrates that an integrated, non-invasive, diagnostic approach provides a thorough analysis of materials and execution techniques of Ernst' masterworks allowing an in-depth knowledge of his highly skilled work

Calcium Ethoxide as Consolidant for Porous Limestones: Influence of the Solvent

Calcium ethoxide nanosuspension, a consolidating product developed during the European Nanomatch project, is here modified by adding two different solvents, 2-butanol and n-butylacetate, chosen for their different boiling points with respect to ethanol, the solvent employed in a previous work to dilute the original product. Fourier transform infrared spectroscopy (µFT-IR) was used to understand how the presence of these new solvents can influence the kinetics of the carbonation process and the pathway reaction. Furthermore, coatings derived from nanosuspensions were maintained for specific time intervals at controlled relative humidity conditions (RH = 50% and RH = 90%); the formed mineralogical phases were characterized by µFT-IR and X-ray diffraction (XRD). Results indicate that the used solvents can influence the kinetic and reaction pathways, while the phases formed at the end of the carbonation process are influenced by both solvents and RH conditions. The effectiveness of calcium ethoxide based product diluted in 2-butanol and n-butylacetate as limestone consolidants was evaluated with drilling resistance measurement system (DRMS) and ultrasound pulse velocity (UPV). The impact on color coordinates was also assessed. The results were compared with those obtained with the same product diluted in ethanol and a commercial nanolime. The use of these solvents gave different and better results in terms of efficac

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

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Linee guida per il bilancio di genere delle Università. Una proposta operativa. (Versione 1.0)

L’obiettivo del documento è quello di fornire delle indicazioni utili e concrete agli Atenei, perché possano intraprendere una sperimentazione del Bilancio di genere. Si tratta di un lavoro che è aperto alla discussione e al progressivo aggiornamento, in una logica partecipativa, che veda le stesse Università come protagoniste e non come semplici destinatarie di indicazioni fornite da terzi. Per tale ragione esso viene proposto nella versione 1.0, che verrà seguita da una successiva edizione aggiornata, frutto delle sperimentazioni che si auspica verranno effettuate presso gli Atenei

Calcium alkoxides for stone consolidation: Investigating the carbonation process

Despite the importance of carbonation in many processes, still the reaction needs investigation. The reaction is essential for the effectiveness of consolidants, based on CaCO3 forming products, used in stone conservation. Research on carbonation of two calcium alkoxides products, developed during the Nanomatch project, is presented in this paper and the results discussed and compared with those reported with the most used nanolimes. Calcium tetrahydrofurfuryloxide (Ca(OTHF)2), dissolved in four different solvents, and calcium ethoxide (Ca (OEt)2), diluted in ethanol, were applied on glass slides and their carbonation kinetics investigated together with their coatings after being kept in uncontrolled and controlled RH conditions (50% and 90%). This allowed to understand the evolution and the phases formed along the process. Carbonation follows the two pathways already reported for alkoxides; it is a quick process and eventually leads to the formation of the most stable crystalline phase (calcite), with high humidity favouring this final step. Alkoxides resulted thus to be suitable compounds for stone conservation, where full carbonation and formation of calcite needs to be obtained for the effectiveness of consolidation

Comparison between mercury intrusion porosimetry and nuclear magnetic resonance relaxometry to study the pore size distribution of limestones treated with a new consolidation product

Pore-space properties, such as pore-size distribution and connected porosity, are relevant factors in the evaluation of the performance of a consolidation treatment. In this study, two different techniques – Mercury Intrusion Porosimetry (MIP) and Nuclear Magnetic Resonance Relaxometry (NMRR) – were adopted to study the compatibility and the efficacy of a new consolidation product for limestones. This work aims at comparing and combining data obtained by MIP and NMRR; to confirm the relationship between the quantitative results of MIP and the qualitative ones of NMRR, a calibration which leads to correlate T2 distribution and pore size distribution has been applied. Experimental results showed that, in most cases, NMRR results agree with MIP data. Therefore, NMRR technique can be considered a powerful tool to evaluate the change in pore size distribution due to the application of a consolidating agent on stone, especially in cases when sampling should be avoided

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

Abstract 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 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