AQ Coating is short for "Aqueous Coating." This is a term for a post-production process where a clear coating, in a water base and applied like ink by a printing press, is applied to the entire surface and used to protect and enhance the printing underneath. It provides a light luster to the printed product, speeds up dry times, minimizes finger prints, and adds more scuff protection. Since aqueous coating makes it problematic for postage and inkjet printing to be applied, it is not applied to mailing sides of postcards.