The treatment of weathered Globigerina Limestone : the surface conversion of calcium carbonate to calcium oxalate

Abstract

This paper focuses on the initial phases of a research programme aimed at investigating the performance of an induced surface conversion of weathered Globigerina Limestone from calcium carbonate to calcium oxalate and the prospects of it being used for the conservation of this stone. This first part of the research concerns the verification of the surface conversion, and the determination of its extent, using X-Ray Diffraction. The testing was carried out on laboratory treated samples and on exposed statuary treated in-situ by others in 2003. The laboratory treated samples consisted of initially salt weathered quarry samples, fresh quarry samples and naturally weathered samples. Both desalinated and non desalinated samples were treated. In addition to these, quarry samples treated in 2003 by others were also tested. The results obtained confirmed the formation of calcium oxalate in all cases, and its extent, relative to the stone’s surface texture and its salt content.