## 4 Conclusions  
The research gave insight into the possibility of extending the use of EOs in the conservation of oil paintings. Indeed, the trial presented in this work was planned not with the purpose of the proper selection of suitable EOs related to the microorganisms isolated from an oil painting, but to lay the groundwork for the development of new control practices which would be suited for this kind of artwork. In conservation, the main limit in the use of plant derivates is the methodology of application, which usually implies the direct contact of EOs with the artwork surfaces. This may cause problems due to the unpredictable reaction with pigments (and other substances used in making paintings) and EOs, such as the potential solvent effect. For this reason, here we tested oregano and cloves EOs, already reported in the literature for their inhibitory activities, focusing the attention solely on the volatile components of EOs, avoiding direct contact with pigments. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & \multicolumn{3}{c}{**CONTACTLESS TEST**} \\ \hline  & ISOLATES & TAXA & OREGANO \\ \hline  & I\({}_{\text{c}}\) & _Bacillus subtilis_ subsp. _subtilis_ & 1.7 \(\pm\) 0.3 cm \\  & II\({}_{\text{a}}\) & Xanthomonadaceae & Total inhibition \\  & III\({}_{\text{a}}\) & _Streptomyces_ & 1.6 \(\pm\) 0.4 cm \\  & IV\({}_{\text{a}}\) & NI & 1.6 \(\pm\) 0.4 cm \\  & V\({}_{\text{a}}\) & NI & 1.8 \(\pm\) 0.2 cm \\  & VI\({}_{\text{a}}\) & _Stenptrophomonas_ & 1.6 \(\pm\) 0.2 cm \\  & VII\({}_{\text{a}}\) & _Pseudomonas psychrotolerans_ & 1.5 \(\pm\) 0.5 cm \\  & VIII\({}_{\text{a}}\) & Xanthomonadaceae & 1.1 \(\pm\) 0.4 cm \\  & IX\({}_{\text{a}}\) & _Cellulosinicribuum cellulans_ & Total inhibition \\  & X\({}_{\text{a}}\) & Penibacillaceae & 1.9 \(\pm\) 0.1 cm \\  & XI\({}_{\text{a}}\) & NI & 1.6 \(\pm\) 0.2 cm \\  & XII\({}_{\text{a}}\) & _Paenibacillus_ sp. & Total inhibition \\  & XIII\({}_{\text{a}}\) & _Bacillus simplex_ & 2 \(\pm\) 0 cm \\ \hline  & I\({}_{\text{a}}\) & _Penicillium chrysogenum_ & ++ \\  & II\({}_{\text{c}}\) & NI & + \\  & III\({}_{\text{a}}\) & _Penicillium chrysogenum_ & +++ \\  & IV\({}_{\text{b}}\) & _Cephalothea fovolata_ & ++ \\  & V\({}_{\text{a}}\) & _A Aspergillus_ sp. & +++ \\  & VI\({}_{\text{a}}\) & _Cephalothea fovolata_ & ++ \\  & VII\({}_{\text{a}}\) & _Cladosporium parahalotolerans_ & + \\  & VIII\({}_{\text{a}}\) & NI & ++ \\  & IX\({}_{\text{a}}\) & _Cephalothea fovolata_ & +++ \\  & X\({}_{\text{a}}\) & _A Aspergillus versicolor_ & +++ \\  & XI\({}_{\text{a}}\) & NI & ++ \\ FUNGI & XII\({}_{\text{a}}\) & _Penicillium chrysogenum_ & +++ \\  & XIV\({}_{\text{a}}\) & Trichocomaceae & + \\  & XV\({}_{\text{a}}\) & Chaetomiaceae & ++ \\  & XVI\({}_{\text{a}}\) & _Penicillium chrysogenum_ & ++ \\  & XVII\({}_{\text{a}}\) & _Cephalothea fovolata_ & +++ \\  & XVIII\({}_{\text{a}}\) & NI & ++ \\  & XIX\({}_{\text{a}}\) & Phaeosphaeraaceae sp. & + \\  & XX\({}_{\text{a}}\) & _Penicillium_ sp. & + \\  & XXI\({}_{\text{b}}\) & NI & +++ \\  & XXII\({}_{\text{b}}\) & NI & + \\  & XXIV\({}_{\text{a}}\) & NI & +++ \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Inhibition halo of oregano and cloves essential oils on bacteria and fungi in contactless tests. The experiment was performed in duplicate. NI = not identified strain. Ethanol 70% was used as a negative control as it did not show any inhibitory effect against the isolates. The results obtained in the present work proved that the oregano and clove EOs, and in particular the volatile components of oregano EO, are able to inhibit the growth of potential oil paintings' biodeteriogens. We hypothesize that an effective method for EOs application could be to flow a thin film of EOs onto an evaporating surface and to place it close to the painting using some supports, so that the vapors of the EOs may homogeneously reach the painting surface, therefore avoiding direct contact of EOs with the pigments.