2.3. Identification of biological contamination
After restoration, micro-organisms infected the painting. In order to identify the contaminants present in the artwork, a simple approach was taken. Almost all colonies consisted of fungi, and microscopical observation of conidiophore structures revealed the presence of Aspergillus sp. as well as Penicillium sp.
2.4. Choosing radiation doses
According to the literature, the appropriated gamma radiation dose to eliminate the identified microorganisms is 6kGy. Then, small samples of the original painting and all materials used in the restoration process were submitted to three subsequent irradiation process using gamma radiation to get the doses: 6kGyFrecommended to decontamination in this case, 10kGyF above what some colour modification has been detected before and 25kGyFstandard dose for sterilisation (Belyakova, 1961; Tomazello, 1994).