Bioinorganic Material─The Crude Ca-oxalate Conservation Film on Historic Stone

A crude conservation film was found that formed naturally on the surface of some historic stone buildings and monuments. It was so well preserved that the stone inscriptions under the film were not damaged though they were made one more thousand years ago. In this contribution, the composition and origin of the crude conservation film were focused. The samples o f the film were analyzed by FTIR, PLM, EDAX, SEM and TEM. The results show that the film consists mainly of calcium oxalate and there is a microbial involvement in the calcium oxalate film. There is no clear dividing line between the carbonatematrix and oxalates film. The transformation layer is about 15um thick. The thin bioinorganic film is very compact non-porous shell and the calcium oxalate is far more acid resistant than that of calcium carbonate. The forming mechanism was discussed and the chemical bionics of this crude film was also researched.