A laboratory investigation of the microbial degradation of cultural heritage

The effect of aging on the microbial colonization of two model systems, "mock paintings" and silk, has been investigated in samples artificially aged. In the case of mock paintings, as compared to untreated controls, aging by heat treatment increases colonization by the two tested fungal species (almost two orders of magnitude in the most aged samples). Relining of aged paintings seems to result in an increase in the colonization by bacteria and fungi if wheat starch paste is used in the relining procedure, In the case of silk fibroin, aging by treatment with wet heat or exposure to a Xenon lamp does increase to a small extent the susceptibility to bacterial invasion. How ever, fungi seem to grow on artificially-aged fibroin but not on the untreated protein. Thus it appears likely that the chemical modifications induced by the two treatments render fibroin a source of carbon and nitrogen utilisable also by fungi, The latter data may be of some relevance to the conservation of silk artifacts of historical or artistic interest.