Reverse osmosis uses ion exclusion to force water containing undesired contaminants through a semi-permeable membrane. A concentration of ions at the surface of the membrane permits the passage of water molecules while rejecting contaminates and impurities.
In window cleaning systems, the purified water from the RO becomes ionically charged by passing it through a De-Ionisation unit called a DI Vessel. The effect is such that the water dynamically attracts dirt, dust, mineral deposits and various organic materials when applied to the surface of the window glass.