The influence of solar radiation on the deterioration of the marble columns in the courtyard of the lions in the Alhambra

Abstract

Studies prior to 1992 on the marble columns in the Courtyard of the Lions in the Alhambra (Granada, Spain) established that the main cause of deterioration was the continuous and high temperature changes to which they are subjected. Over 15 years after these studies, this contribution evaluates the present state of the columns by measuring the evolution of the decay that had been observed previously, together with new decay, paying special attention to the microenvironmental conditions of the courtyard in order to understand better the relation between environmental factors and the evolution of the decay. The most significant pathology is scaling, which is closely related to the intensity and exposure time of sunlight on the various columns. Although hardly any scaling is apparent on those columns that were not already affected by 1990, it has increased on the others. Microcracking is also identified as the initial phase of deterioration caused by sunlight and thermal gradients.