Many stone-made historic buildings have a yellowish layer called 'patina' on their external surface. In some cases, it is due to the natural ageing of the stone caused by chemical-physical reactions between the surface of the stone and the environment, and in other cases it is the result of biological activity. The origin of these patinas can be also be due to ancient protective treatments. The use of organic additives, such as protein-based compounds, in lime or gypsum-based patinas is a traditional technique, which has been used in past centuries for the conservation and protection of stone materials. The thinness of the patinas ensures that microscopic techniques are irreplaceable for their analysis. Optical Microscopy, Fluorescence Microscopy, Scanning Electron Microscopy together with an Energy Dispersive X-ray Spectrometer, and Electron Microprobe are the microscopic techniques used for the characterization of these coverings, providing very useful information on their composition, texture and structure.
Bibliographical noteFunding Information:
This study has been financed by project BIA2003-0473 (Spanish Ministry of Education and Science), by a “Ramon y Cajal” contract (MAdB) (Ministry of Education and Science). CVC thanks the CSIC (Spanish Council for Scientific Research) Thematic Network for Historical and Cultural Heritage for a scholarship cofinanced by the European Social Fund. Thanks are also given to the Research Support Centres of Electron Microscopy “Luis Bru” of the Complutense University of Madrid (UCM).
- Oxalate film
- Protective treatment