The addition of ethanol, which is fully miscible in water yet, less polar than Water reduces its solubility. This reduction of solubility results in precipitation of least soluble salts first or the salt which is not soluble in solvents less polar than water.
Pole pockets on banners are something that can cause a bit of confusion. This is compounded by the fact that some companies do things differently when producing banners with pole pockets.
7501 Series is a high strength standard banner used for average size banners in heavier wind conditions, it is one side smooth and printable. 7504 Series is a standard banner designed for common use, it is one side smooth and printable. 7508 Series is a heavy weight banner used for pole, street or large scale banners, it is two side smooth and printable with a blockout layer for complete opacity.