## 3 Results
### Improving Susceptibility of Consolidants to Degradation through Treatments with Biocides  
The efficacy of applying commercial products based on quaternary ammonium salts with biocidal properties (Biotin R\({}^{\otimes}\), Biotin T\({}^{\otimes}\) and Preventol\({}^{\otimes}\) RI 80) to prevent fungal growth was evaluated.  
_On slide cultures._ Almost all tested biocides had toxic effects on the following strains: _Aspergillus_ sp. S1, _Bipolaris_ sp. P2 and _Bipolaris_ sp. M7 (Figure 10). Although the germination of _Aspergillus_ sp. S1 spores on consolidants was microscopically observed, the viability test was negative in all cases (Figures 10 and S7). In the case of _Bipolaris_ sp. P2 and _Bipolaris_ sp. M7, for both consolidants, although some spores germinated or poor mycelium developed, the viability test was negative. _Ullocadium_ sp. H1 did not germinate on either of the consolidants treated with Biotin R\({}^{\otimes}\) but developed mycelium on TDC treated with Biotin T\({}^{\otimes}\) and Preventol\({}^{\otimes}\) RI 80.  
Figure 9: The growth of fungi on the experimental models without consolidants. (**a**,**d**,**g**,**j**) _Aspergillus_ sp. S1; (**b**,**e**,**h**,**k**) _Bipolaris_ sp. M7; (**c**,**f**,**i**,**l**) control.  
_On the frescoes._ Treatments of Paraloid(r) B72 and TDC consolidants with biocides applied to the surface or to the mixture prepared before application to the frescoes resulted in the prevention of colonization by the fungal strains used in experiments.  
All the fungal species inoculated developed colonies on the frescoes used as controls. Colonial growth was not noticed in any of the experimental variants treated with Biotin R(r) (Figure 11b,c) or Biotin T(r) (Figure 11d). In the case of Preventol RI 80, the treatment applied to the surface of the Paraloid(r) B72 only allowed partial germination of the spores and no formation of mycelium (Figure 11e). In none of these experiments were the spores or hyphae found to be viable, which demonstrates the toxic effect of biocide on fungal spores and, in consequence, the prevention of consolidant degradation.  
Frescoes consolidated with TDC and treated with biocides on the surface and in the form of a mixture were judged to be protected from fungal decomposition because they were not colonized (Figure 12). However, three exceptions were identified: the strain _Bipolaris_ sp. M7 developed a brown-black mycelium on the frescoes treated with Biotin R(r) (Figure 12b), Biotin T(r) (Figure 12c) and Preventol R1 80 on the surface (Figure 12d,e). In all cases, the mycelium ceased its vital activity until the end of the experiment. Combining these results with those obtained from the experimental painted models, we do not rec  
Figure 11: Resistance of Paraloid® B72 to _Aspergillus_ sp. S1 colonization after biocide treatment. (**a**) Culture developed on frescoes without biocide; (**b**) masses of spores on BRs; (**c**) masses of spores on BRm; (**d**) masses of spores on BTs; (**e**) masses of spores on Ps.  
Figure 10: Viability of fungal strains on Paraloid® B72 and TDC coupled with biocides.  
ommend the use of Preventol(r) RI 80 to prevent colonization because the hyphae firmly adhered to the TDC surface and cleaning attempts would cause tearing.