STUDYING DEGRADATION OF CRYPTS

Crypts, mainly originating from the early Christian catacombs with the function for burial and worship, were very common in Europe during the Romanesque and Gothic periods. A lot of them suffer processes of degradation with different types of decay. Sometimes moulds, fungi, algae and bacteria are present on the shafts of the columns, sometimes salt efflorescence is spread along the masonry and on the base of the columns. Anyway both the chemical and biological alterations as well as the mechanical deterioration are strongly correlated with the changes in relative humidity and temperature, that play a key role in the activation of the damage. An environmental control, often cited as a desirable means of reducing deterioration, when incorrectly applied could exacerbate the damage. So, it is important that the environmental conditions for limiting the damage are selected on the basis of studies that accurately reflect the real situation. Here we focus on the study of some ancient Italian crypts with the aim to investigate the influence of the environment on the degradation processes, assessing possible connections between those findings and microclimatic behaviour. We detailed the change of the damage distribution both spatially and over time, making use of non-destructive methods. They consist of sampling and chemical/biologic analyses, condition assessment by environmental monitoring, image processing of photographic documentations and in situ observations. Furthermore building location, historical background, stone typology and features, natural-artificial lighting and ventilation, are taken into account. Once this had been addressed, a plausible explanation for the dynamic deterioration is given, some strategies are suggested and compared with the literature. They are both structural such as consolidation procedures, after removing contamination sources, and environmental, such as the control of indoor flow, as predicted by fluid dynamics simulations. Other possibility is to use Light Emitting Diode systems to control biodeterioration, eliminating chemicals means, such as bleach or steam, to remove growth. Keywords: Degradation; Environmental control; Thermodynamic behaviour; Fluid dynamics