Frescoes, deterioration

A very modern ecological aspect of lichens is biodeterioration, which means the deterioration and destruction of ancient frescoes, coloured windows of cathedrals and old buildings by incrustation with lichens. The lichen Dirina massiliensis Durien et Mont, has already destroyed the painted frescoes of the Palazzo Farnese in Caprarola, Italy. Similar damages have been noted on Greek sculptures and on the Arch of Trajan. Fourier transform microscopy has shown that the lichens produce oxalic acid, which converts the calcium carbonate of the substrate to calcium oxalate, changing the structure of the surface (Edwards et al. 1993). 

Figure 7 Badly deteriorated frescoes from the Palazzo Farnese, Caprarola, Italy, built in 1547, and now the subject of extensive lichen encrustation which now requires extensive conservation.

Makzetti ScrePA (2000) Marzetti, B. Scirpa, R L alterazione del nero d ossa nella pittura ad affresco studi delle font e sperimentazione tecnico-scientifica Deterioration of bone black in fresco painting study of the sources and experiments Kermes la rivista del restauro 13 37 (2000) 39- 5... 

Because the porous mortar backing of a fresco allows for the transport of dissolved salts to the back of the painting, deterioration can take place when these... 

---