So what IS efflorescence?
Efflorescence is the deposit of water soluble salts resulting from a process which involves many different factors. When any one of these factors gets out of balance per se then efflorescence can occur. Weather, water chemistry, construction practice, masonry materials, structure design, and cleaning practice are some of the factors which influence whether or not an installation will effloresce. Typically the signature of efflorescence is a visible deposit of whitish salts or material near the grout joints which may continue to reappear even after cleaning. Similar to the white powder left in a drinking glass when a glass of water is left to evaporate, efflorescence is caused by minerals that are soluble in water being dissolved and transported to the surface of the grout as the water evaporates.

Is efflorescence always a salty affair?
Typically efflorescence is attributed to the deposit of salty substances but efflorescent substances may also include acids, bases, or colloidal gels. According to G.C. Robinson of the American Ceramic Society1 "they may be crystalline substances of definite chemical composition or amorphous substances indefinite in composition. The word is used to label the substance and the process by which it was formed."