Characterization of deteriorated protectives and consolidants applied on stone materials and their eventual bio-removal

Abstract

Today, there is a great awareness of the conservation of monuments. The development of techniques and research on plastic materials led to the advancement of new technologies and application methods, which were adapted for the restoration and conservation of stone materials. Restoratores and Conservators contributed to the diffusion of these treatments and application methodologies, though no preliminary experimental tests had been undertaken to ensure their efficiacy. This entailed the development of degradation mechanisms, such as the generation of secondary products due to the chemical interaction between the product applied and the substrate or the environment, and compromised the stability and the aesthetical aspect of the artefact. For this purpose, a laboratory operating methodology was developed to evaluate the efficacy of commercial products which have been widely used for the restoration of stone materials, and to characterize any associated degradation mechanisms. The commercial products were carefully selected and applied on stone specimens. The results obtained were compared with those obtained from a spread sampling of Venetian surfaces treated in the past. Thus, it was possible to characterize, compare and contrast polymeric groups and commercial products widely used in conservation. Chemical FTIR and μFTIR analysis, microscopic observations, SEM-EDS studies, sponge tests, natural and artificial ageing in Solar Box, evaluation of the resistance to growth of mould, were carried out in the laboratory and allowed the complete evaluation of the selected products. The laboratory operating methodology experimented have been already applied on the industry, in order to evaluate the applicability of experimental products of Tenax spa factory and promote the related commercial growth. A positive feedback was recorded. Moreover, preliminary reports of the results obtained from the sampling of Venetian surfaces treated in the past, were considered useful for the monitoring of historical-artistic surfaces of interest by the Venetian Superintendent.