Removal of Calcareous Concretions from Natural and Manufactured Stone Archaeological Artefacts through the Use of CO2 Water Solutions

In the Yococu edition of 2008 the results of experimental research concerning the use of a CO2 solution applied to natural stone of calcareous origin (marble and travertine) and silicate (tuff) were presented. Chemical and physical analysis indicated the validity and effectiveness of this method. In the meantime the research has continued on ceramics and the results are reported in the present edition of YOCOCU. The method is based on the property of aqueous solutions of CO2 to dissolve and remove the carbonate component of concretions, found on the surface of porous objects, making it easier to remove them. These concretions can hide significant decoration details and obscure the historical, social and artistic values of an ancient object but their removal could be harmful to the object itself and are also the cause of their state of conservation. During the course of the experiment it was possible to develop different treatment procedures having a different duration of application time depending on the type of material. The evaluation was first conducted on test samples of the same nature of the ceramic objects to be treated in the second phase of the experiment. The trial was conducted taking into consideration the state of conservation of the object to be restored, the conservator health and the care of the environment. The method has proven to be valid for ceramic materials as was the case for the stone artefacts.