Abstract

In the past few years INAF – Palermo Astronomical Observatory "G. S. Vaiana" has paid attention to the realization of preventive conservation projects for archival documents, bibliographic materials and scientific instruments deriving from its over-two-century research activity.

In 2017, in collaboration with the University of Palermo, some interventions which were focused on the assessment and re-housing of part of the historical archives took place. A new conservation/restoration project regarding the oldest core of the historical library started in 2019 and is still ongoing.

In 2019, a pilot project was also proposed involving the scientific collections on display at the museum. A survey of the assets conditions is ongoing and a series of environmental monitoring campaigns have been started in order to evaluate the microclimate effects on the collections. A risk management approach has been adopted to assess collections care priorities and plan timely solutions and sustainable long-term strategies.

The present contribution summarizes the results of these experimental projects and highlights the benefits of the preventive conservation practice in the management of the collections.

1 Introduction

In the past few years, several initiatives of preventive conservation have been carried out at the Palermo Astronomical Observatory on the scientific heritage kept in its historical archives, library, and museum. Books, instruments, and documents can be considered as a small LAM (Library-Archive-Museum) unit, in that they are strictly related to one another, having been produced for the same purpose: facilitate research in the fields of astronomy and meteorology.

Preventive conservation is a fundamental practice within collections management policy since it includes any intervention aimed at preventing or reducing assets’ deterioration. This can be achieved by checking the risks coming from the environment in which the different materials are exposed, stored and transported.

By managing the risks, future invasive treatments can be avoided.

2 Preventive Conservation Project at the Museo della Specola

Since 2018, the Astronomical Observatory of Palermo has been working on a preventive conservation project for the collections on display at the Museo della Specola (see Figure 1), aimed at establishing intervention priorities and identifying which improvements can be made in the environmental conditions for the long-term benefits on the collections [1]. The Museum displays about one hundred objects, mainly scientific instruments, but also some art works.

Different aspects of the context in which the objects are situated have been studied and some of the risks to which they are exposed have been identified by mean of: a) the compilation of condition reports, upon the analysis of the conservation state of the assets and investigation of the potential causes of the damages observed, and b) the monitoring of the values of temperature and relative humidity indoors and the sampling of a selection of gaseous pollutants.

2.1 Thermo-hygrometric Monitoring of the Museum Rooms

Between 2013 and 2014, a first thermo-hygrometric monitoring campaign was undertaken to study the microclimate conditions of the exhibition rooms. The recorded values fell outside the ranges established by Standard UNI 10829/1999 for each material in the collection. In 2018 the air conditioning system was turned on in all the rooms, aiming to keep the temperature at 19 °C in winter and at 24 °C in summer. An additional one-year environmental monitoring was started to evaluate the effects and effectiveness of the adopted measures.

Preliminary studies have highlighted some critical issues.

Relative Humidity (RH): The RH values recorded during both campaigns have shown that the microclimate of the museum is greatly influenced by the external climate. In 2019, the average daily RH values and the maximum daily excursions have increased in comparison with 2013-2014. The activation of the air conditioning systems seems to have altered the previous indoor situation, resulting in wider daily excursions and increased internal RH values that, in some cases, are similar to the values recorded outside the museum (see Figures 2 and 3).

Temperature (T): it seems that the air conditioning system was able to perform, in most of the rooms, a degree of control over the temperature values, keeping them lower and more stable than those recorded between 2013 and 2014.

These data are to be further verified during the current monitoring which has started in May 2021. All the collected records will allow us to analyze and improve the microclimatic situation of the rooms or at least to limit its impact on the objects; data could also contribute to further studies aimed at reducing unnecessary emissions and energy consumption in order to render “green”, responsible, and efficient the management of the museum, in line with the international efforts.

2.2 Sampling Campaign to Test Air Quality in the Museum and Inside the Showcases

As a first step, we chose to investigate the presence of some pollutant which are quite common in historic buildings located in urban areas and harmful for the objects in the museum: sulfur dioxide (SO₂),formic acid (CH₂O₂), acetic acid (CH₃COOH), nitrogen dioxide (NO₂), and hydrogen sulphide (H2S)[2][3][4].

Radiello® passive sampling devices, produced by ICS Maugeri (Padova, Italy), have been placed in the exhibition rooms and in some display cases of the museum, in the historical library, in the archives, and in the museum storage. The aim of the campaign was to investigate the presence of the selected pollutants and to identify, where possible, their likely source.

The sampling has just ended and laboratory analysis is ongoing.

3 Preventive Conservation Interventions in the Historical Library and Archives of Palermo Observatory

The “paper heritage” of the Observatory has also been the object of preventive conservation projects in the past years.

In 2017 some interventions which were focused on the assessment and re-housing of part of the historical archive took place. Considering the variety of the materials (correspondence, meteorological, and astronomical observations, photographs, drawings, and bound materials), it was necessary a careful planning of the activities that took into account both the limited time of the project and the needs of this heterogeneous collection. A preventive conservation project was developed, starting from the collection assessment, in order to identify risks and to plan strategies to mitigate or remove them. The conservation survey pointed out the necessity of re-housing for some of the materials, identifying the highest risk in their consultation, as the most widespread damages were due to improper manipulation and mechanical stress which incurred throughout the centuries. The materials, which were selected and included in the project, were cleaned, stored in new boxes and folders (made with materials suitable for long-term conservation), and replaced on the shelves (see Figure 4). During the survey some specific damages with high risk of losses were identified and treated to avoid further harms.

Following the first project, in 2019 a new one-year conservation/restoration project was carried out: it regarded the oldest core of the historical library, the so-called Fondo Piazzi. The collection includes more than 800 monographs dating from the 16th to the beginning of the 19th century. In this case too, the starting point was a conservation survey: conservation assessment was improved by the use of a database in which was stored every information about the condition and the features of each book. It was decided to prioritize the intervention on the books with on-going damages with a high risk of losses that could be consolidated in a short time, and to re-house in purpose-built cases the books in the worst conditions, waiting for future appropriate treatments in a laboratory. The whole collection was cleaned, 98 books were stabilized and 89 books were re-housed in suitable boxes, made with long term conservation materials. These interventions have stabilized the whole collection, improving its condition.

4 Acknowledgments

The authors thank the Department of Physics and Chemistry “E. Segrè" of the University of Palermo, Dr. Vincenzo Franzitta (Department of Energy, Information Engineering and Mathematical Models, UNIPa) and Mr. Filippo Mirabello who collaborated for the definition of the monitoring campaign and the analysis of the recorded data. Sincere thanks also to the restorer Marco di Bella and Prof. Dario Camuffo for their suggestions and encouragement.