Conservar Património (Jan 2009)
Microbial biodeterioration diagnosis of the 16th century frescoes from the Casa de Fresco de Sanches Baena (Vila Viçosa, Portugal)
Abstract
The Casa de Fresco de Sanches Baena is located in Vila Viçosa (Southeast Portugal) and is a small semi-underground building constructed in a garden over a well and used as a cool refreshing place by the owners. The frescoes that cover the ceilings and the walls present rich mythological scenes together with musical angels, shells, porcelain and other decorative elements, which make them an especially rich and unusual example of this art form. The paintings possess an intense polychromy suggesting the use of a rich palette comprised of different pigments to obtain various colours and hues. Unfortunately, due to partial abandonment and lack of repair the paintings are in an advanced state of degradation exhibiting partial detachment of paint layers and mortars, salt efflorescence and abundant biological colonisations. This work reports the study of the frescoes to allow the identification of the different microorganism populations and to assess their role in the deterioration of these paintings. For the microorganism sampling, sterile cotton buds and stylets were used and the biological materials collected in sterile recipients. The microbiological study by optical microscopy and scanning electron microscopy allowed the isolation of 34 fungi strains and 32 bacterial strains in the four painted panels that compose the frescoes. The predominant bacterial strains were the Gram+ and Gram- strains from the genera Bacillus and Pseudomonas, respectively. As to the fungi populations, the dominant strains identified were from the genera Cladosporium spp. and Penicillium spp. The microbial activity in the 4 panels was assessed by enzymatic essays, namely, dehydrogenase (DHA). The results showed that the decayed areas of the painting present higher dehydrogenase activity and therefore this enzyme seems to be a good indicator of biodegradation.
Keywords
