The decay of the polysiloxane resin Sogesil XR893 applied in the past century for consolidating monumental marble surfaces

A study of the deterioration micromorphologies and a chemical investigation of the alteration products of an experimental polysiloxane resin used for consolidating marble sculptures in Venice was undertaken several decades after the initial treatments. A multianalytical study was carried out on a number of microfragments sampled from four Venetian monuments treated in the 1960s and ‘70s. The Fourier Transform InfraRed spectroscopic analysis (FTIR and μFTIR) was used to identify the conservative treatment applied, to confirm its chemical nature (whose formulation has never been confirmed) by comparing the results with the literature, and to investigate both its behaviour under a very aggressive environment and the possible related deterioration products. Microscopic observations of cross-sectioned samples (mainly through SEM-EDX analysis) were conducted to investigate the resin morphology and distribution into the pores, and to identify the possible residual presence of other conservative products previously or subsequently applied. In addition, water absorption by means of the sponge contact method was used to verify the present water repellency of the treated surfaces. The methodology adopted proved to be adequate to the aim of the research and gave useful information about the performance of the resin examined over time.