Efflorescence\xa0is the loss of water (or a solvent) of crystallization from a hydrated or solvated salt to the atmosphere on exposure to air. … The water, with the salt now held in solution, migrates to the surface, then evaporates, leaving a coating of the salt.\xa0Example\xa0is Gypsum (CaSO4.\xa0Efflorescence\xa0is a deposit of salts, usually white, formed on a surface, the\xa0substance\xa0having emerged in solution from within either concrete or masonry and subsequently precipitated by evaporation.