In recent years, the uses of Desulfovibrio vulgaris bacteria arise to be a very quoted method to remove the sulphates from stone material belonging to cultural heritage [1]. This biological method has been patented in the 2006 by a group of research of the University of Milan and optimized by the spin-off company Micro4yoU Srl [2]. The sulphate-reducing bacteria D. vulgaris, thanks to their metabolism, are able to dissociate gypsum into Ca2+ and SO42+ ions; SO42+ ions are then reduced by the bacteria into H2S, whereas the Ca2+ ions react with carbon dioxide to form new calcite. Compared with other more traditional methods, this biological procedure results in a more homogeneous removal of the surface deposits and preserves the patina noble under the black crust [3]. Despite the increasing number of successful applications of Desulfovibrio vulgaris on different lithotypes [4 and 5] little has been done on painted surfaces. Aim of the present study is to evaluate the effectiveness and harmfulness of the method for removing the sulphates efflorescence on paintings surfaces. In particular, the potential harmful effects of the bacteria on pigments will be evaluated and monitored on specimens prepared ad hoc. A set of specimens of mural painting, with different pigments, was prepared and cured for seven months. The pigments used (yellow ochre, vermilion, green earth, yellow Pb-Sn, azurite, red lacquer, white lead, smalt blue) were applied by different methods (fresco and organic binders). By NMR analysis, a preliminary study was carried out to choose the best delivery system to entrap the bacteria for this biological cleaning and the Carbogel is selected. Then the specimens, soiled with gypsum, were cleaned with the system bacteria/Carbogel and with Carbogel to evaluate only the effect of the bacteria on the pigments. By this work, we carried out all the colour measurements on the specimens, before their soiling with gypsum and after the cleaning treatments. These measures show a good efficacy of the biological method to remove the soiling and a small alteration of the original colour.
Biocleaning method on painting layer: preliminary tests for monitoring the effect of sulfate-reducing bacteria on pigments
L Luvidi;A M Mecchi;V Di Tullio;
2015
Abstract
In recent years, the uses of Desulfovibrio vulgaris bacteria arise to be a very quoted method to remove the sulphates from stone material belonging to cultural heritage [1]. This biological method has been patented in the 2006 by a group of research of the University of Milan and optimized by the spin-off company Micro4yoU Srl [2]. The sulphate-reducing bacteria D. vulgaris, thanks to their metabolism, are able to dissociate gypsum into Ca2+ and SO42+ ions; SO42+ ions are then reduced by the bacteria into H2S, whereas the Ca2+ ions react with carbon dioxide to form new calcite. Compared with other more traditional methods, this biological procedure results in a more homogeneous removal of the surface deposits and preserves the patina noble under the black crust [3]. Despite the increasing number of successful applications of Desulfovibrio vulgaris on different lithotypes [4 and 5] little has been done on painted surfaces. Aim of the present study is to evaluate the effectiveness and harmfulness of the method for removing the sulphates efflorescence on paintings surfaces. In particular, the potential harmful effects of the bacteria on pigments will be evaluated and monitored on specimens prepared ad hoc. A set of specimens of mural painting, with different pigments, was prepared and cured for seven months. The pigments used (yellow ochre, vermilion, green earth, yellow Pb-Sn, azurite, red lacquer, white lead, smalt blue) were applied by different methods (fresco and organic binders). By NMR analysis, a preliminary study was carried out to choose the best delivery system to entrap the bacteria for this biological cleaning and the Carbogel is selected. Then the specimens, soiled with gypsum, were cleaned with the system bacteria/Carbogel and with Carbogel to evaluate only the effect of the bacteria on the pigments. By this work, we carried out all the colour measurements on the specimens, before their soiling with gypsum and after the cleaning treatments. These measures show a good efficacy of the biological method to remove the soiling and a small alteration of the original colour.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
