Setup of a sustainable indoor cleaning methodology for the sculpted stone surfaces of the Duomo of Milan

Abstract

Cleaning is a fundamental phase of the conservation and maintenance activity of the cultural heritage. It is required to be highly effective in the removal of undesired deposits, controllable at every stage and gradable, selective, and completely respectful of the substrate. Moreover, cleaning procedures which can also assure to be harmless to the environment and the operators are particularly valued nowadays. According to these general guidelines, in the present work a sustainable approach for the cleaning of indoor surfaces of the cultural heritage is presented. A methodology based on agar gel was setup and preliminary tested on pilot areas. It has been then applied to the stone sculpted surfaces of the "Fuga in Egitto" high-relief of the Duomo of Milan. A multi-analytical approach was carried out during the setup phase to compare the efficacy of different cleaning conditions in terms of agar concentration, application time and presence of additives. Hence, spectrophotometric measurements, optical observations, ESEM-EDX analyses, Fourier Transform Infrared Spectroscopy, and X-Ray Diffraction were performed. Specific attention was paid to the aesthetic features of the sculpted surfaces before and after the cleaning. For this purpose, spectrophotometric data have been analysed by multivariate analysis techniques such as Principal Component Analysis and Hierarchic Cluster Analysis. The overall intervention has been monitored to evaluate the cleaning results and to confirm the absence of any damage to the stone substrate. The application of agar gel proved to be effective in removing soluble salts and soot particles, as well as very respectful of the valuable sculpted surfaces. This methodology is also totally safe for both the operators and the visitors, it is based on a natural and low-cost raw material, and it is low time-consuming. It can be therefore considered as a sustainable alternative to the traditional procedures.

Cleaning of Easel Paintings

“…by brushing) or as a rigid gel (see Fig. 4.2), leaving almost no residues as reported in the literature (Gulotta et al 2014;Cremonesi 2006). Recently, agar gels have also been loaded with nanostructured cleaning fluids (microemulsions), for the removal of lipophilic materials (wax) from porous surfaces (Gorel 2010).…”

Research of a complex fire-induced pollution on the marble relief from the Pushkin state museum of fine arts collection

“…Fundamental restoration of sculptures is impossible without conducting integrated studies of contamination composition and exhibit surface condition and accurate identification of the materials of sculptures, bas-reliefs and coatings. Studying the contamination before cleaning marble objects has been common practice in recent years [1][2][3][4][5][6][7][8][9][10][11][12]. Most often, these are pollutions associated with the environment [1][2][3][4][5][6][7][8][9] or appeared due to contact with other materials [10][11][12].…”

Ineducable us: the applications and contexts of microscopy used for the characterisation of historic building materials

“…The work of Gulotta et al [44] describes the effects of varying cleaning methods of marble sculptures investigated by optical and electron microscopy. The analysis contributes to the optimised choice of cleaning method and provides documentation of material effects also at the microscale.…”

“…For example the understanding of salt dynamics is advanced by direct in-vivo observation of salt crystallisation [47], (though of course this work is clearly scientifically valuable). The effects of conservation treatments, such as cleaning and consolidation, are also amenable to investigation using microscopy [27,44]. This can be to characterise samples taken from in-situ treatments, and the results used to correlate to performance against requirements (for example penetration depth) and also longer term durability behaviours.…”