Introduction
Efflorescence is an unsightly white staining on brickwork commonly caused by salt in the bricks themselves or by mortar drying out quickly. The salt is comprised of one or more of the sulphate and carbonate compounds of sodium, potassium, calcium and magnesium. As the salt solution evaporates the salt is deposited on the surface of the brickwork. This will disappear when wetted, but will recur once the work dries out. It can occur at any time of the year but it is most noticeable after a long wet period followed by quick drying and sunshine. While efflorescence may be unsightly, especially as its most common form occurs on new brickwork during the initial drying out period, it is rarely damaging. It normally does not recur unless conditions are allowed to persist, which can promote its periodic regeneration.
The salts can originate not only from the bricks but also from the constituents of the mortar, ground water, other building materials and even the ground where the materials were stacked prior to use.