# Factors Affecting the Efficiency of Hydrophobic Coatings--Experience from Application on Sandstone
## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \begin{tabular}{c} **Sample** \\ **Series** \\ \end{tabular} & \begin{tabular}{c} **Sample** \\ **Sample** \\ \end{tabular} & \begin{tabular}{c} **m\({}_{1}\) (g)** \\ \end{tabular} & \begin{tabular}{c} **m\({}_{2}\) (g)** \\ \end{tabular} & \
\begin{tabular}{c} **m\({}_{3}\) (g)** \\ \end{tabular} &
\begin{tabular}{c} **m\({}_{3}\)–m\({}_{1}\) (g)** \\ \end{tabular} \\ \hline \multirow{4}{*}{2x/2w} & H\(-21\) & 240.29 & 240.72 & 240.26 & \(-0.03\) & \\ \cline{2-6}  & H\(-22\) & 237.39 & 237.82 & 237.39 & \(0\) & \multirow{2}{*}{\(-0.07\)} \\ \cline{2-6}  & H\(-23\) & 235.00 & 235.33 & 234.84 & \(-0.16\) & \\ \cline{2-6}  & H\(-24\) & 236.87 & 237.23 & 236.79 & \(-0.08\) & \\ \hline \multirow{4}{*}{3x/2w} & H\(-33\) & 238.53 & 238.89 & 238.36 & \(-0.17\) & \\ \cline{2-6}  & H\(-34\) & 233.09 & 233.49 & 232.99 & \(-0.1\) & \\ \cline{1-1} \cline{2-6}  & H\(-35\) & 241.57 & 241.93 & 241.47 & \(-0.1\) & \\ \cline{1-1} \cline{2-6}  & H\(-36\) & 238.01 & 238.40 & 237.98 & \(-0.03\) & \\ \hline \hline \end{tabular}  
m\({}_{1}\)—initial dry mass of untreated sample, m\({}_{2}\)—mass of sample with Funcosil SNL after 2 weeks of curing, m\({}_{3}\)—dry mass of sample with Funcosil SNL after all water absorption tests.  
\end{table} 
Table 6: The mean dry mass of the coating remaining in the samples after all water absorption tests—Funcosil SNL. Based on the laboratory comparison, Antipluviol S can be recommended for the protection of stone facades of buildings, as well as of stone statues and monuments in exteriors in climates with heavy and frequent rains. Before its application, the weather forecast must be taken into account to secure a curing time of 2 weeks without rain. In less humid climates, Funcosil SNL can be useful as protection against occasional and moderate rain. Of course, producers also work on the research and development of their products. In this way, shortly after our research, the producer of Antipluviol S changed the information leaflet. In the new leaflet, 0.8 kg\(\cdot\)m\({}^{-2}\) is given as the assessed amount for the application to reach sufficient saturation, whereby no breaks for drying should be left between individual coating layers. In this way, much more chemicals will be consumed. The consumption in the presented study was some 0.1 to 0.3 kg\(\cdot\)m\({}^{-2}\), following previous recommendations. Now, not only the economic, but also the environmental impact must be considered. All such coatings are declared as dangerous, highly flammable, and harmful for environment. At the university, further research will be directed towards the minimum consumption necessary for an optimum effect. Finally, some remarks as to the comparability of the presented research with similar reports [6; 13; 14; 15]: the testing conditions and treated stones were too different. In the presented study, curing time proved to be the most important factor. While 2 days and 2 weeks were compared here, other authors used more than 2 weeks for the curing, and some of them even tried much longer times. This makes any comparison with published reports impossible.