Modern techniques as basis for the preservation of antiques

Cultural assets exhibited or stored in museums and archives are subjected to deterioration. Microorganisms can be responsible for this deterioration, together with several microclimatic conditions, ageing and the chemical structure of substrates. Therefore, an accurate control of the climatic and microbiological conditions in museums and archives, to be maintained at non-dangerous levels for the exposed or stored objects, is a requisite for any preservation/conservation strategy. To choose the appropriate measurements against microbial growth on objects of art, it is necessary to obtain an overview about the complexity of the present microbial populations. Traditionally, microbiology research carried out in this field was mainly based on classical cultivation methods. Nowadays, it is generally accepted that cultivation methods recover less than 1% of the total microorganisms present in environmental samples. In addition, extensive cultivation strategies require more sample material than could be obtained from art objects. Nevertheless, in the last years, Molecular Biology has been adapted for the investigation and monitoring of cultural assets, and has revealed a more complete picture about the microbial communities colonising different substrates, as wall paintings, stone, glass, and paper materials. The aim of the present study is to make available to restorers and curators the know-how of our working group in the application of modern techniques, including culture-dependent as well as non-destructive culture-independent techniques, for the microbiological investigation of cultural assets. This Project comprises two international collaborations with two independent well known institutions. The first institution, the ICPAL - "Istituto Centrale per il Restauro e la Conservazione del Patrimonio Archivistico e librario" Rome (Italy), will collaborate with us in the investigation of valuable parchment samples -as the Archimedes Palimpsest- and with the second institution, the EURAC-Institute for Mummies and the Iceman, Bolzano (Italy), we will study the deterioration of the mummies located at the Crypt of the Capuchin Monastery of Palermo (Italy). An exhaustive study of the causative agents of deterioration of parchments and mummies, including climatic and microbial investigations, will be carried out. The obtained results will be used to establish, together with the restorers and responsibles of the corresponding museums and archives, a monitoring of the abiotic and biotic agents responsible for the deterioration of the selected objects and furthermore, to develop a concept to maintain these agents under controlled conditions. When necessary, conservation measures will be applied, i.e. cleaning and/or disinfection.

The goal of this project was to make available to restorers and curators the know-how of our working group in the application of microbiological and molecular methods to monitor the causative agents of the biodeterioration affecting peculiar cultural objects. The project comprised international collaborations with two outstanding institutions; the first one, the ICPAL - "Istituto Centrale per il Restauro e la Conservazione del Patrimonio Archivistico e librario" Rome (Italy) - actively collaborated in the investigation of valuable ancient parchment samples. The second one, the EURAC -Institute for Mummies and the Iceman, Bolzano (Italy) - collaborated in the investigation of human remains and other related materials. A combined research strategy, including climatic, microbial, molecular, chemical and microscopical analyses, was performed inside the frame of this project. In collaboration with the ICPAL, ancient parchment manuscripts, all showing a peculiar deterioration phenomenon -they were defaced by red to purple spots associated with localized destruction of the collagen fibers- were investigated. Results derived from the combined research strategy applied in this study allowed, for the first time, to establish a relationship between the biodeterioration phenomenon affecting the parchments and the presence of specialized microorganisms detected in all investigated cases. The common denominators were halophilic ("salt-loving") members of the Actinobacteria, and fungal species of Aspergillus. Additionally, the hypothesis that a relationship exists between the phenomenon of purple spots on ancient parchments and that of the "red heat" phenomenon, known to be present in some products manufactured with marine salt, was suggested for the first time. Within the framework of the "Sicily Mummy Project" and in collaboration with the EURAC, the human remains located at the Capuchin catacombs of Palermo were investigated in this project. These catacombs contain over 1800 preserved bodies dating from the 16th-20th centuries AD, showing severe signs of biodeterioration. Results derived from this study showed: first, a poor indoor air quality inside the catacombs, with a high concentration of fungal spores - in some areas of the crypt the concentrations even exceeded 2000 spores per m3. Medically, this amount must be classified as posing a potential health risk to visitors and furthermore, is not conducive to the conservation of the human remains. Second, constructional problems and the environmental conditions at the catacombs allowed the infiltration of water and the formation of salt deposits all over the walls, which offer a special habitat for halophilic microorganisms. These microorganisms were responsible for the extensive rosy discoloration observed on the catacombs walls. Salt cracks were detaching and contaminating the surfaces of other mummified remains and related materials. Moreover, specialized microorganisms belonging to taxa well-known for their cellulolytic and proteolytic activities were detected on the materials. These specialized microorganisms are threatening the conservation of the mummies themselves. Finally, the presence of insects is worth mentioning, which were mainly contributing to the deterioration of the coffin wood and the clothing of the mummies. The obtained results have been delivered to the restorers and responsible personnel of the ICPAL and the EURAC, enabling: 1) the cataloging of the abiotic and biotic agents responsible for the deterioration of the investigated parchments and human remains, 2) the evaluation of the biodeterioration risk affecting the investigated objects, 3) the development of a concept to maintain these biological agents under controlled conditions. When necessary, conservation measures - i.e. cleaning and/or disinfection - were applied by restorers.