Non-invasive analytical technique to address water uptake on stone surfaces: The implemented Contact Sponge Method (i-CSM)

Abstract

Abstract The assessment of capillary rise rate is a recommended test in Cultural Heritage diagnostics to evaluate the evolution of stone textural properties and decay, and performances of conservation treatments. Beside laboratory tests, diverse non-invasive and non-destructive, in-situ methods were developed in order to establish the monitoring for monumental structures and decorative apparatus: Karsten tube, Mirowsky pipe and contact sponge methods (CSM). The comparison between the diverse techniques demonstrated high comparability between the datasets obtained with the CSM (UNI 11432:2011) and those recast with capillary absorption. However, the dataset collected with the conventional method is affected by high standard deviation due to several variables, mainly operator-dependent. The adoption of a pocket penetrometer, coupled with the use of a thicker sponge, aimed at parameterizing the load upon the surface. The implementations allowed a higher reproducibility of the measures, as well as the possibility of applying increasing pressures. In this study the i(mplemented)-CSM was adopted to test the adsorption behaviour of a set of ornamental stones (Macigno Sandstone, Breccia Aurora, Rosso Verona and Vicenza Stone) both un-weathered and weathered by freeze-thaw ageing and salt weathering. A correlation between the maximum open pore radius and an increase in water absorbance at higher loads was established. The preliminary promising results wait to be further validated on larger datasets.