Biodeterioration on oxidic glasses: part II: biocorrosive reasons for appearance of Glaspest of antique glasses like Mecklenburger Waldglas

摘要

Glaspest is a consequence of biodeterioration. It is a barrier of diffusion, which prevents the corrosion of the motherglass. The appearance of Glaspest is caused by the output of organic acids by fungi. In this case Alternaria, Aspergillus andPenicellium and other were found. Organic acids, produced in culture filtrates of these fungi, were analysed by High Performance Liquid Chromatography (HPLC). Acetic acid, oxalic acid, citric acid, gluconic acid and finally fumaric acid were identified as the corrosive media. Laboratory experiments with glass powder and organic acids show a close relation between the microbiological attack and the appearance of the Glaspest layer, in particular whedellite is a consequence of the attack of oxalic acid.Experiments with culture filtrates indicate an increase of pH. Alkaline oxides are dissolved and can attack the glass network, quartz nascents. At last Glaspest can be reproduced by fungi settlement at model glasses. All these results indicate thepresence of a three-phase-model mechanism of biodeterioration on glass, especially for glasses with a high amount of alkaline oxides. The first phase is the phase, in which microorganisms colonialize the glass surface. Then the output of organic acidsstarts, followed by a neutralisation of alkaline oxides of the glass volume. The result of this phase is the appearance of Glaspest. At the second phase dissolved alkaline oxides attack the Glaspest, pH increases and quartz appears. During the constantattack of oxalic acid whedellite emergence. The last phase is a passive one. Whedelitte converts to calcite in the presence of water and carbon dioxide.