Evaluation of silicone based products used in the past as today for the consolidation of Venetian monumental stone surfaces

The commercial consolidating siloxane compounds EAS 40, Rhodorsil Consolidante RC90 and RC80, and the silicone water repellent agents Rhodorsil H224 and Hydrophase were carefully applied to stone specimens and tested to ascertain their chemical nature and their stability under oxidative stress and degradative environments. The resins were applied to laboratory samples (Carrara marble and Vicenza white limestone specimens) and subjected to controlled natural weathering and artificial ageing. The film morphology and the penetration depth was observed and measured by SEM-EDS determinations, while the stability of the resins was monitored by FTIR, SEM-EDX, colorimetric measurements and sponge tests. The results were compared with those obtained from a spread sampling of Venetian surfaces treated in the second half of the XX c. with Sogesil XR893 and X54-802, silicone resins which are no longer on the market. The overall results prompted a number of considerations on the effects of the resins applied to stone materials and offered the authors the opportunity to make a practical contribution to current practices in the consolidation of stone materials.