Development and application of a cleaning system for the thinning of layers of carbonation of wall surface painted sensitive, realized by means of thickened aqueous solutions at pH weakly acid

Author: Nicola M., Scalesse R., Coluccia S. ; Typology:  Conference proceedings

Licence: © Nardini Editore Lo Stato dell'Arte 4, Atti del VI Congresso Nazionale IGIIC, Siena 2006;
Year: 2006;  Language: Italian

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The study comes from the need to solve the problem of cleaning and consolidation of sites within cryptoporticos frescoes unearthed at the ancient Roman town of Formia. The underground environment had encouraged the formation of very consistent and thick carbonate deposits  that had developed on top of wall paintings of lesser hardness. After disappointing results obtained with the application of traditional techniques (ion exchange resins, ammonium carbonate, mechanical cleaning, etc..) it has been developed a tailored system which could find application also in analogous cases. The system developed has yielded good results on several fronts. Of utmost importance is also a property of not introducing soluble salts, combined with the quality, verified by measurements of pH, of self-limiting in the time that guarantees the stop of the effects of hypothetical residues.
One can not overlook the good operating speed of, which allows to minimize the contact of the surface painted with dense solution containing water. Many systems traditionally used, in fact, involve protracted contact with aqueous solutions often not adequately thickened and containing generally aggressive agents having the time to spread through the natural porosity of the substrate and going on deeply damaging the substrate. The aqueous solutions, particularly if free and / or applied for long periods, also tend to swell and brittle carbonate layers even at considerable depth and often lead to extended phenomena of recrystallization surface (the latter phenomenon is of particular intensity in the case of use of cleaning agents such as ammonium carbonate).

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