Biodegradability of Products Used in Monuments’ Conservation

Abstract

The conservation procedures in monuments’ restoration foresee three types of interventions on stone materials:cleaning; protecting; consolidating. In these treatments several kinds of natural and synthetic products are applied. Most of them have a temporary function and should not remain on the monument, but some have the specific objective to protect or to consolidate the stone surface and their permanence is expected to last for a few years. For these treatments different classes of organic polymers are normally used and, in order to maintain their activity, the structure and composition of the product should remain unchanged with time. The aim of this work is to verify the rapid biodegradability of some organic products used in conservative treatments of monuments, In reality, we use the biodegradability test to verify the bioresistance of these conservative treatments, and consequently their lasting action. The readily biodegradation test has been made following the EEC method C6 “closed bottle BOD” modified for the particular field of application, using the Velp respirometer apparatus. The microorganisms used in the test have been isolated from the stones of seven monuments, located in the centre of Florence. The microoganisms have been collected using contact plates containing nutrient agar pressed on the stone surface. The strains selected are two bacteria: -ST/B3Micrococcus sp.; -SC/L1Bacillus sp.;and an hyphomycete: - SG/F1Ulocladium sp.The restoration products used as test substances are: Paraloid 872 (acrylic resin); Silirain 50 (alkyl alcoxy silane oligomer); Akeogard CO (fluoroelastomer). The preliminary results obtained under these experimental conditions may be indicative of a low biodegradability of the products examined. Thus, it is possible that the freshly applied products possess a good bioresistance.