THE CENTRAL INSTITUTE FOR RESTORATION
AND CONSERVATIVE DESIGN

The complex of environments that make up the Ipogeo dei Cristallini, with its refined decorations, constitutes a real challenge in terms of conservation; a challenge made more difficult by the objective of opening the monument to the public. The typical environmental conditions of underground environments, characterized by high relative humidity and low temperatures, and above all the variation of these values, represent a constant threat to the conservation of the decorative elements, subjected to the risks associated with the movements of the water inside. of the structures.

The Central Institute for Restoration has engaged in 2021 in a campaign of investigations aimed at obtaining a complete knowledge of the Hypogeum of the Crystals. The indispensable prerequisite of any restoration is in fact the in-depth knowledge of what is being worked on, in all its aspects: its history, the constituent materials, its behavior over time, the mechanisms of degradation in progress.

On the one hand, therefore, its structure, the geological context in which it is located, the materials and techniques with which its extraordinary pictorial decorations and other ornamental devices were made more than 2000 years ago have been studied in depth. (stucco, terracotta, marble), on the other hand, the factors and mechanisms that contribute to its gradual deterioration, mainly linked to the interaction with the environment, were analyzed.

Thanks to the 3D survey of the whole complex and the carrying out of physical, chemical and biological investigations (monitoring of the microclimate; aerobiological surveys and culture of samples; UV fluorescence; infrared b / w and false colors; luminescence induced by visible light – VIL ; X-ray fluorescence; analysis and observation under the microscope of micro-samples of original material), and thanks to the careful and irreplaceable observation of the surfaces by the restorers, it was possible to arrive at a full knowledge of the Ipogeo dei Cristallini, even in its stratifications: the sequence of the creative phases, the composition of the plasters, the overlapping of layers and brushstrokes, the pigments used, including the precious Egyptian blue, cinnabar and red lacquers.

To understand the mechanisms of degradation, the first step was the installation of a microclimatic monitoring system which allowed, and will allow for the future, to detect in real time the climatic parameters of the underground environments, the air flows coming from outside, the incidence of precipitation and the variation of daily and seasonal cycles. The analysis of the deposits of foreign substances present on the surfaces, as well as of the formations of a biological nature, helped to define a complete picture of the phenomena taking place in the hypogeum, an essential prerequisite for developing the most effective conservation strategies. The most worrying factor of degradation is linked to the presence of soluble salts, contained in the water with which the walls are soaked: the action of the salts in fact produces the disintegration of the plaster and the pulverization of the color, in addition to the formation of encrustations hard and difficult to remove surfaces.

The work of the Central Institute for Restoration therefore aims to compose an overall vision of the Ipogeo dei Cristallini and its relations with the environment, because only in this way will it be possible to design and implement the interventions that will allow this extraordinary monument to continue to exist over time, and to be known and appreciated by the community.