involves the application of silver, zinc or tin (or a combination of) to glass that has already been formed and taken off the float line. The coating is softer than online coated glass therefore why it is referred to as soft coat. Furthermore, if silver is used (and it often is) the offline coating can oxidise if exposed to normal air. For this reason, offline coated glass must be used in an insulated glass unit (IGU). Sealing the coating in between two pieces of glass protects it from outside air and sources of abrasion. Soft coats have been developed with both Low E (insulation) properties as well as solar control.