The primer(Alkali metal salt,Silicic acid compound) infiltrates stone and the crack in concrete.
And, a surplus element forms the hydrophobe thin film on the surface.
Because titanium dioxide (TiO2) is accumulated to a Surface hydrophobe thin film, the layer of silica (SiO2) and titania (TiO2) is formed.
In addition, the thin film of titanium dioxide (TiO2) is made on the surface.