Chemical Parameters and Development of Biodeteriogens

All artefacts, except for the very few preserved in modified atmosphere, are directly in contact with the air of outdoor and indoor environments, and are therefore subject to the chemical action of atmospheric constituents. This gives rise to transformations in the materials, changing their chemical composition, and their physical and mechanical characteristics. Atmospheric pollution, i.e. the phenomenon that changes the natural atmospheric composition both quantitatively and qualitatively, accelerates the deterioration of artefacts, because of the interaction between the components of the object and the substances present in the atmosphere. The effects of the atmosphere on materials of artistic value have aroused increasing interest over recent decades, especially because of the vast proportions and severity of the phenomenon of acid deposition (Fassina, 1987; Rossval, 1988; Schuster et al, 1991; Guidobaldi et al., 1993; Sabbioni, 1997; Daniel, 1996). While many works have been published which address the direct action of atmospheric pollution on artefacts, studies on the effects of pollution on the microflora present on the surface of objects are less numerous (Gehrmann et al., 1988; Aireset et al., 1991; Klokkernest, 1991; Manes et al., 1991; Nimis et al., 1992; Piervittori et al., 1993). Atmospheric pollutants may have inhibiting or lethal effects on microflora, depending on their nature and concentration.