Microclimatic monitoring of the plaster casts of the Trajan’s Column in the Museum of Roman Civilisation (Rome)

In recent years, the control of the micro-climate in museum environments or in historical buildings has assumed a role of great importance for the protection of the artefacts exhibited and for planning cost-effective and strategic preservation policy. The process of degradation indeed, defined as a result of progressive and cumulative material decay, strongly depends by environmental variables and their changes. Rapid changes and/or strong gradients in temperature and/or relative humidity, are the main causes of internal stress and of material surface detachments. Compared to new museums, historical ones often do not dispose of ideal conservation parameters, and they need specific conservation environments, considering the so-called historical climate, i.e. the microclimate to which the Cultural Heritage has adapted over the time. This is the case of the Museum of Roman Civilisation (Rome), which has been closed since 2014 and hosts a huge and valuable collection of plaster casts, such as those of the Trajan’s Column made by Napoleon III in 1861-1862 and gifted from Vatican City to Rome City Hall in 1953. In view of the imminent museum reopening and restoration, it is essential to define the actual level of microclimate quality, compared to the expected one, considering also economic and regulatory aspects and the future welfare of the artefacts. The research is focused on the response of the materials to the micro-climate by evaluating the incidence of temperature and relative humidity, presumably the main chemical and physical degradation factors for the plaster casts. A multidisciplinary diagnostic approach (i.e. Hyperspectral Imaging, Raman Spectroscopy, Infrared Spectroscopy) is also planned to characterise the constituent materials, to suppose the manufacturing techniques of the casts and to identify the degradation forms. The analysis of the complex interaction between the dynamics of the climate and the need for the conservation of the artefacts under conditions of maximum stability represents the starting point for proposing a sustainable restoration of the Trajan’s Column plaster casts of the Museum of Roman Civilisation and a future exhibition project that will allow their valorisation and exposure.