Calcium alkoxides as alternative consolidants for wall paintings: Evaluation of their performance in laboratory and on site, on model and original samples, in comparison to conventional products

Bourguignon, Elsa; Tomasin, Patrizia; Detalle, Vincent; Vallet, Jean‐Marc; Labouré, Martin; Olteanu, I.; Favaro, Monica; Chiurato, Matteo; Bernardi, Adriana; Becherini, Francesca

doi:10.1016/j.culher.2017.07.008

Cited by 17 publications

(30 citation statements)

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“…Through this carbonation process, the starting alcohol evaporates and is released. This behavior makes them suitable for consolidation of carbonate supports, such as wall paintings, plasters and building stone materials [6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2018

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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.

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Section: Introductionmentioning

confidence: 99%

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

et al. 2018

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“…During the European Project Nanomatch [14] two calcium alkoxides, (Ca(OTHF) 2 and Ca(OEt) 2 ), were developed and tested as new consolidants for stone and stone-like substrates as well as alkaline reservoir for wood. Their performance as consolidants for indoor and outdoor applications on wall paintings was evaluated both in laboratory and in the field in comparison with commercial products and the results published in recent papers [15, 16]. In particular, short-term surface colour change induced by the application of the consolidation treatments was investigated in laboratory using colorimetric measurements carried out on wall paintings mock-ups.…”

Section: Introductionmentioning

confidence: 99%

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

Becherini

Durante²,

Bourguignon

et al. 2018

Chemistry Central Journal

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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.

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“…The calculated ΔE* values for cinnabar, French Ochre, and Lapis Lazuli pigment particles before and after the 28 days of immersion in DAP were determined to be 3.5, 3.4, and 4.2, respectively (Table 1). Though these values are above the threshold of color change detected by the human eye [40], they are still below the established value (ΔE* ≤ 5) accepted for cultural heritage consolidation treatments [16,[41][42][43][44][45][46][47][48].…”

Section: Cinnabar French Ochre Lapis Lazulimentioning

confidence: 94%

“…∆L* describes the change in luminance, ∆a* the change in red/green components, and ∆b* the change in yellow/blue components. While generally ∆E* ≤ 2 is widely acceptable as the value detectable by the human eye [40], a color difference of ∆E* ≤ 5 has been established as the threshold in the field of cultural heritage to evaluate color change after a conservation intervention such as consolidation treatment [16,[41][42][43][44][45][46][47][48].…”

Section: Characterization Of Pigment-dap Interactionmentioning

confidence: 99%

“…The color values of the pigments before immersion into the DAP solutions and after 28 days of reaction with DAP, as well as the ∆E* values, are listed in Table 1. In this research, it was demonstrated that, while the color difference ∆E* of most pigments tested, including cinnabar (deep red), French ochre (yellow), lapis lazuli (blue), chalk (white), and raw sienna (yellow), were above the threshold detected by the human eye (∆E* > 2), with the exception of burnt umber (brown) which showed no detectable color change (∆E* < 2), they all showed ∆E* values below the accepted threshold (∆E* ≤ 5) for cultural heritage studies [16,[41][42][43][44][45][46][47][48]. Slightly darkening (−∆L*) was observed for most pigments, except raw sienna.…”

Section: Summary Of Color and Phase Changes In The Pigmentsmentioning

confidence: 99%

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Investigation of the Optical, Physical, and Chemical Interactions between Diammonium Hydrogen Phosphate (DAP) and Pigments

Pasco²,

Balonis

et al. 2019

Sustainability

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This research investigates and evaluates the optical, physical, and chemical interactions between a diammonium hydrogen phosphate (DAP) solution and seven pigments commonly encountered in archaeological and historic fresco and secco wall paintings and polychrome monuments. The pigments include cinnabar, French ochre, chalk, lapis lazuli, raw sienna, burnt umber, and red lead. The raw pigments were analyzed before and after the interaction with the DAP solution, and the reaction products resulting from the contact of the pigments with the DAP solution were evaluated to obtain a comprehensive understanding of the effects of diammonium phosphate on the color, morphology, and chemical composition of the pigments. The results indicated no significant changes of the color or of the chemistry of cinnabar, French ochre, and lapis lazuli. Carbonate-containing primary and secondary (found as impurities in earth pigments) pigments, such as chalk and calcium carbonate, were transformed into calcium phosphate, though without a significant change in color. Phase and strong color changes occurred only for the red lead pigment, associated with the transformation of red lead into hydroxypyromorphite. These data established the parameters and identified the risks of the direct application of DAP solutions on pigments. Further research will be undertaken to assess the potential use of DAP as a consolidant of wall paintings and other polychrome surfaces through testing on wall painting/polychromy mockups and on-site archaeological/historic painted surfaces.

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Calcium alkoxides as alternative consolidants for wall paintings: Evaluation of their performance in laboratory and on site, on model and original samples, in comparison to conventional products

Cited by 17 publications

References 17 publications

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

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

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

Investigation of the Optical, Physical, and Chemical Interactions between Diammonium Hydrogen Phosphate (DAP) and Pigments

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