A new method to prepare calcium oxalate films for marble protection

Artificial calcium oxalate films have been applied to protect sculptures, monuments, and buildings made of marble due to their potential protective capacities. Unfortunately, artificially prepared calcium oxalate films are usually loose, and easy to peel off in contrast to the natural ones. In this paper, a new method was developed for the preparation of a compact and cohesive calcium oxalate film, using ethylene glycol as an additive. The morphology, elemental composition, structure, and crystal phase of the film were analyzed by SEM, EDX, IR, and XRD, and the protective effects were investigated by acid resistance test, while its adhesion to the underlying marble by the Scotch tape test. The porosity, water absorption, and color of treated marble were also assessed. The results showed that a calcium oxalate film with a compact structure, good adhesion, and a protective effect against acid rain can be successfully obtained by including ethylene glycol as an additive. With the new preparation method, a better bond between the stone and the film is obtained which contributes to solving the spalling problem of the artificial calcium oxalate films.