Bioremoval of Sulphate Layer from a 15th Century Polychrome Marble Artifact

This case study shows the application of viable bacterial cells for removing undesired deposits from the surface of a stone polychrome bas-relief, exhibited at the Interdisciplinary Gallery of Sicily Palazzo Abatellis (Palermo). Diagnostic studies carried out during the restoration were aimed at characterizing the technique of execution and understanding the degradation processes. The results of the XRF and FTIR investigations showed that on large areas of the artifact’s surface, stratified deposits with a significant presence of sulfates were present. For bioremoval of the deposits, viable bacterial cells belonging to the species Desulfovibrio vulgaris, were utilized in gelled solution form, evaluating and comparing the effectiveness of this cleaning with that of the desulfating agents usually employed. The results demonstrate that by using the colonised substrate as a nutritional source in their natural metabolic processes, this bacterial species can be used to obtain high efficiency and selectivity of action, representing a valid alternative to the use of traditional chemical agents