Calcium oxalate films on stone surfaces: Experimental assessment of the chemical formation

This work considers the possibility that calcium oxalate found on stone art ifacts has been formed after the oxidation of organic substances applied on the surface of the stone. Laboratory tests, performed with hydroxyl radica l as oxidant, seem to support this hypothesis. The organic compounds subjec ted to the tests were chosen from those used int he past for the conservati on treatment of works of art. both whewellite and weddellite have formed, d epending on the organic substance. Fourier transform infrared (FTIR) and X- ray diffraction (XRD) spectra provide the necessary experimental evidence.