Effects of microwave heating for the conservation of paper artworks contaminated with Aspergillus versicolor

The conservation of the cultural heritage, such as old books, manuscripts, paintings etc. is particularly important, for both their artistic and historical values. These types of materials are often exposed to usage or storage conditions where efficient biodeterioration mechanisms take place. Deterioration of these materials occurs naturally as a result of aging, but it can be accelerated by poor storage conditions (humidity) that lead to fungi growth and negative chemically effects. Firstly, this work concerns with isolation and identification of a fungal species that infects an 18th century book. The identification was based on morphological analysis made by light and SEM microscopy and on ribosomal DNA loci amplification and sequencing. One fungal strain, Aspergillus versicolor, was identified as responsible of book biodeterioration. Then, A. versicolor was used as biodeteriogen to contaminate paper samples exposed two degradation processes (exposure to wet atmosphere and to acidic attack) simulating storage conditions of 18th century book. Secondly, microwave heating at three different temperatures (30, 58 and 63 °C) was applied on paper samples affected by spots originating from A. versicolor in order to evaluate the effectiveness of microwave in cleaning of artworks from fungi. Scanning electron microscopy and cellulose degree of polymerization were used for visual inspection and characterization of the paper samples before and after the treatments respectively. The best results were obtained by exposure of paper samples for few minutes at 58 and 63 °C, while the lower temperature (30 °C) didn’t inhibit A. versicolor’s growth.