The University of Granada takes part in a European project that, within the VI Framework Programme, aims to improve maintenance and restoration techniques of cathedrals and historical buildings from an interdisciplinary point of view. Geologists, like those of the research group directed by Eduardo Sebastián Pardo, of the Department of Mineralogy and Petrology of the University of Granada, play an essential role in this network of architects, restorers and physicists.
These researchers from Granada have experiences in a lot of projects all through more than fifteen years. They have collaborated to maintenance works of palaces, churches and cathedrals of Jaén, Palma de Mallorca, Vitoria, Logroño, Baza (Granada) and Utrera (Sevilla). Among their current research works are the Alcazaba in Almería, Medina Azahara in Córdoba and the Puerta de las Granadas, in the Alhambra; they are evaluating which maintenance products are the most appropriate to restore them.
Specifically, the speciality of Sebastián Pardo and his team is the fight against damages saline compounds cause inside the stone, leading to the fissure spread. “Salts and acid rain enter the porous system through small and irregular cracks. By the stone warming and the sudden drop of environment humidity, saline solutions can crystallize inside, in the most superficial areas, causing subefflorescences which bring about serious damages in rocks”, explains the UGR researcher.
Interventions in Granada
Sebastián Pardo, collaborator to numerous interventions in Granada like those in the Cathedral, in Gates and City Walls of the Arab age and in different Nasrid Palaces of the Alhambra, points out that forcing these substances to go out makes restoration specialists´ work easier but, at the same time, it causes aesthetic problems which can be seen in a lot of churches in Andalusia and Spain.
This slow deterioration process takes already place in Nature before the stone is extracted for the building work. According to a study of this research group, the alteration of ornamental porous materials by salt crystallization increases when the physical-environmental conditions of the stone are forced. Different crystallization-inhibiting substances, always in minimal proportions, were incorporated into saline solutions to test it and study the interaction with stones. It is to say, they tested the variability of these processes in the laboratory depending on different factors, like climatological ones.
Geologists usually analyse the state of alteration of the materials, suggest sorts of cleaning and maintenance products and monitor the process once it starts. They proposed laser cleaning for the lower part of the Puerta del Perdón (Gate of Forgiverness) of the Cathedral of Granada, where ornamental stone was especially dilapidated.
These works are part of the European project SALTCONTROL, which started at the beginning of the year. The first meeting took place in Granada, in January. The Universities of Ghent, London, Munster and Prague, the Andalusian Institute of Historic Heritage and the Dutch Department of Maintenance are present in these studies.
Reference: Prof. Eduardo Manuel Sebastián Pardo.
Department of Mineralogy and Petrology
Phone number: 958 243340 / 248535.
