## 3 Results
### Experiment 1: Selection of Methods Used for Assessing Photoautotrophic Growth on Plaster Coatings
The red dot represents the control sample, the blue dots represent the tested samples; arrows represent shifts in color components. dL* scale represents the achromatic component (lightness of the object); da* axis (green–red) and db* axis (blue–yellow) represent the respective color components. hydrophobic substrates, i.e., MP and MPGS, the overall growth was higher than for S and SGS types of substrates. Macroscopic observations also revealed that for the S and SGS samples, the forming biofilm was localized on the outer areas of the surface without a colonized center, while for MP and MPGS, the growth occurred throughout the whole surface area. For samples inoculated with the M1 method, green biofilm could also be visible on the solid 3N-BBM medium layer outside of the technical materials' surface. For the M2 method, higher variability between sample repetitions was noted. For both methods used, a high correlation was observed between the results acquired by visual assessment and spectrophotometric \(\Delta\)E determination. \begin{table}
\begin{tabular}{c c c c c c} \hline  & \multicolumn{2}{c}{**Cell Density**} & \multicolumn{1}{c}{**Chl-\(a\)**} & \multicolumn{1}{c}{\(\Delta\)E} & \multicolumn{1}{c}{**ATP**} \\ \hline \multirow{4}{*}{MP} & Cell density & 1.000 & 0.790 & 0.999 & 0.975 & 0.00 \\ \cline{2-6}  & Chl-\(a\) & 0.790 & 1.000 & 0.770 & 0.902 & 0.20 \\ \cline{2-6}  & \(\Delta\)E & 0.999 & 0.770 & 1.000 & 0.967 & 0.40 \\ \cline{2-6}  & ATP & 0.975 & 0.902 & 0.967 & 1.000 & 0.60 \\ \hline \multirow{4}{*}{MPGS} & Cell density & 1.000 & 0.997 & 0.727 & 0.342 & 0.80 \\ \cline{2-6}  & Chl-\(a\) & 0.997 & 1.000 & 0.674 & 0.995 & 1.00 \\ \cline{2-6}  & \(\Delta\)E & 0.727 & 0.674 & 1.000 & 0.006 & \\ \cline{2-6}  & ATP & 0.342 & 0.995 & 0.006 & 1.00 & \\ \hline \multirow{4}{*}{S} & Cell density & 1.000 & 0.750 & 0.660 & 0.812 & \\ \cline{2-6}  & Chl-\(a\) & 0.750 & 1.000 & 0.660 & 0.318 & \\ \cline{2-6}  & \(\Delta\)E & 0.660 & 0.830 & 1.000 & 0.729 & \\ \cline{2-6}  & ATP & 0.812 & 0.318 & 0.729 & 1.000 & \\ \hline \end{tabular}
\end{table} 
Table 2: Correlation indicators (R\({}^{2}\)) calculated between results acquired with the tested methods. Figure 2: Color change measured for silicone plasters. (**A**)—silicone plaster (S) measured after inoculation; (**B**)—silicone plaster (S) measured after 14 days of incubation; (**C**)—silicone plaster (S) measured after 28 days of incubation; (**D**)—silicone plaster with primer and silicone paint (MPGS) after inoculation; (**E**)—silicone plaster with primer and silicone paint after 14 days of incubation; (**F**)—silicone plaster with primer and silicone paint after 28 days of incubation. The red dot represents the control sample, the blue dots represent the tested samples; arrows represent shifts in color components. dL\({}^{*}\) scale represents the achromatic component (lightness of the object); da\({}^{*}\) axis (green–red) and db\({}^{*}\) axis (blue–yellow) represent the respective color components. For the correlation of the spectrophotometric color change determination method and the cell density evaluation, lower dependence was found for the S-type substrate than for other materials. Additionally, the most significantly low dependence (R\({}^{2}\) = 0.006), indicating a very weak correlation (close to no correlation), was found for the MPGS substrate, occurring between results acquired with the spectrophotometric color change assay and luminometric ATP measurement. Such occurrence is most probably connected with the high RLU values noted for MPGS samples tested after 14 days of incubation with simultaneously low values calculated for chlorophyll \(a\) concentration. Spectrophotometric color change determination showed a mostly strong or very strong correlation to other tested methods. The results of the visual evaluation, performed in accordance with Section 2.4.6, are presented in Table 3.  
The degree of fouling for all tested technical materials increased linearly over time.