The chalky white bloom on brickwork gets treated as a stain, something to scrub off and forget. It is better understood as a receipt. Salt does not appear on a wall by itself; it arrives dissolved in water that came from somewhere, moved through the masonry, and evaporated at the face. The deposit is the record of that trip.
The white is salt the wall carried out
Soluble salts exist in most masonry materials, in the units, in the mortar, and in the ground below. When water passes through the wall it dissolves them and carries them along. At the surface the water evaporates and the salt is left behind as a crystalline deposit. Three ingredients are required and all three must be present: a source of salt, water to mobilise it, and a path to the surface. Removing any one of them ends the problem, and only one of them is usually practical to remove.
New-construction bloom versus a symptom
Not every occurrence means something is wrong. New masonry contains construction water and it has to leave, so a bloom appearing in the first months on new brickwork is common, usually self-limiting, and often gone after a season or two of weathering. What is not normal is the same deposit returning year after year on an established wall, or appearing on one specific area, or reappearing weeks after cleaning. That pattern is a wall with an ongoing water supply, and the deposit is pointing at it.
Removing it without making it worse
Start dry. A stiff bristle brush on a dry wall removes a surprising amount, and dry removal avoids redissolving the salt and driving it back in. What is left often responds to water and a brush, worked in small areas and rinsed. Proprietary efflorescence removers exist for stubborn deposits and should be tested on an inconspicuous patch first. Acid is the risky option: it can etch the brick face, damage lime mortar, and sometimes causes a worse secondary bloom, so it belongs last on the list rather than first. Whatever the method, do not clean a wall that is currently wet.
Finding the water, which is the actual job
Look above the deposit before looking at it. The usual sources are a leaking or overflowing gutter, a downspout discharging against the wall, failed or missing flashing at a sill, parapet, or roof junction, a defective coping letting water into the top of the wall, sprinklers or irrigation overspray hitting the masonry, and rising damp where a wall wicks moisture from the ground. The location of the bloom is informative: a horizontal band suggests a specific entry point above it, while a general low-level appearance across an elevation suggests ground moisture. Timing helps too. A deposit that appears after every heavy rain and fades between them points at a defect that only leaks under driving conditions, whereas one that persists through dry spells is being fed continuously, which narrows it to irrigation, a plumbing leak, or ground water.
The related problem you do not want
Sometimes the salt crystallises inside the pore structure rather than at the surface, and that version is a different order of concern. The crystals grow within the brick and exert pressure from inside, which spalls the face off in flakes. It shows up as crumbling and loss of the fired skin rather than as a white deposit. The response is the same, find and stop the water, but the damage already done is permanent and the affected units eventually need replacing.
Frequently asked questions
Is efflorescence structurally serious? The deposit itself is harmless. What it indicates, water moving through the wall, can lead to serious problems including freeze-thaw damage and internal salt crystallisation, so it is a symptom worth acting on rather than an emergency in itself.
Will sealing the wall stop it? Usually not, and it can make things worse. A surface sealer does not remove the water, and a film-forming product traps moisture behind it, which pushes the crystallisation inward where it does real damage.
Why does it keep coming back after cleaning? Because cleaning removes the salt but not the water supply. Recurring deposits mean finding and fixing the source, whether that is flashing, gutters, irrigation, or rising damp, rather than scrubbing again. Freestanding hardscape shows the same pattern, and on those walls the culprit is often man-made rather than meteorological, which is why a San Diego hardscaping crew checks sprinkler throw before anything else.