efflorescence on brick

White crust on brick is salt, not mildew

Efflorescence is mineral salt left when water leaves the masonry. Bleach does not solve the moisture, and scraping it like mildew can cut the brick.

Mildew is green or black and biological. Efflorescence is white, crusty, and chemical in the mineral sense: salts dissolved inside the masonry, carried out, and left when the water evaporates. Killing it is the wrong idea. It was never alive. A mild, appropriate cleaning can remove the crust that is already on the face. If the wall keeps wicking water, the crust returns.

We will not attack historic brick with muriatic acid because a homeowner wants it “bright.” Acid on the wrong brick is how faces dissolve. If acid is even on the table, it is a specific masonry decision, named in the quote, not a default.

If the white showed up with a leak, a bad cap, or irrigation on the wall, fix the water or you will hire the wash again. We will point at the likely source. We will not rebuild the wall.

The service this belongs to is Brick and masonry cleaning.