Methods for physical, chemical and biological cleaning of historic stone-masonry monuments

The restoration process of historic stonemasonry monuments is described in this article. The intervention has to be conducted according to the specific character of the monument while recovering its original appearance. The restoration process of the principal facade of the Church of San Lorenzo el Real, Burgos (Spain) is described in this article, as an example of a historical monument located in an urban environment. In the first place, the history was researched and a compilation was made of all the extant documentation on its constructive evolution and the nature of its materials. We characterized the different types of limestone and we analyzed the mortar bonds in the masonry. Once the characteristics and the properties of the materials were known and their degree of decay, cleaning techniques were selected. The programme of work successfully renovated the church building, through the restoration of its main facade.