Paolo Dionisi-Vici

An Analytical Method for the Determination of the Climatic Distance between Different Microclimates for the Conservation of Wooden Cultural Heritage Objects

Abstract This paper describes a statistical methodological approach for the comparison of different microclimates. This method was developed as a tool for choosing a new microclimate for temporary moves. At the present stage of development, this method is not intended to be used for identifying harmful conditions. The proposed method is based on experimental evidence indicating that the sensitivity of wooden objects to environmental fluctuations can differ from object to object, depending on many physical and mechanical parameters. Some objects could be affected by fluctuations that would not be significant for other objects. The parameter adopted in this work is equilibrium moisture content, that is the equilibrium value that a wooden object would tend to maintain under stable temperature and relative humidity values for a long period of time. It must be considered potential because in a fluctuating climate it is never reached. The methodology is based on two parts. The first describes in a mathematically simplified way how climate is perceived by objects with different sensitivities. The second analyzes the climatic distance between different climatic data sets using the mathematical technique of principal components analysis, according to the previously defined objects sensitivity. As a test of the proposed method, four different microclimatic cases studies are analyzed and the results described.

Wireless Sensor Platform for Cultural Heritage Monitoring and Modeling System

Results from three years of continuous monitoring of environmental conditions using a wireless sensor platform installed at The Cloisters, the medieval branch of the New York Metropolitan Museum of Art, are presented. The platform comprises more than 200 sensors that were distributed in five galleries to assess temperature and air flow and to quantify microclimate changes using physics-based and statistical models. The wireless sensor network data shows a very stable environment within the galleries, while the dense monitoring enables localized monitoring of subtle changes in air quality trends and impact of visitors on the microclimate conditions. The high spatial and temporal resolution data serves as a baseline study to understand the impact of visitors and building operations on the long-term preservation of art objects.

The influence of dovetailed cross beams on the dimensional stability of a panel painting from the Middle Ages

Abstract This paper describes experiments carried out to determine the influence of dovetailed cross beams on the dimensional stability of a panel painting from the Middle Ages. Besides a serious cup (transverse distortion), the panel featured an unusual longitudinal distortion, a bow, mostly originating from bending in the proximity of the middle cross beam. Because of its localized occurrence, bending appeared to be caused by the crossbeam somehow pushing on the walls of its channel. Thanks to the cooperation offered by the curator and the restorer, some non-damaging tests were performed to measure the distortions of the panel, with and without the cross beams, after conditioning it in different climates. Processing and analysis of the measurement results demonstrated that the bow of the panel increases as the wood moisture content decreases. This led to the conclusion that the bow is actually produced by forces exerted by the cross beam along the panels length, according to a mechanism named thrust transformation. By this mechanism the cross beam partly transforms the panels tendency towards cupping, into a bow distortion.