White Powder on Brick and Block

Where the mineral comes from

Masonry and mortar contain soluble salts, largely calcium compounds left over from the cement itself. When water moves through the wall it dissolves those salts, carries them to the surface, and evaporates, leaving the mineral behind as a white crystalline deposit. Specifically, cement contains calcium hydroxide, which dissolves readily in the water moving through fresh masonry; once that solution reaches the surface and the water evaporates, the calcium hydroxide reacts with carbon dioxide in the air and converts into calcium carbonate, the same chalky white mineral that forms limestone. The material was always inside the wall. What you see is the end of a chemical journey, which is why a wall can be cleaned perfectly and bloom again after the next wet spell.

Primary efflorescence is normal; secondary efflorescence is a signal

Masonry professionals draw a real distinction here. Primary efflorescence happens during and just after construction, driven by the water already mixed into fresh mortar and brick as they cure, and it is expected to taper off within a year or two as the readily available salts near the surface get used up. Secondary efflorescence shows up well after that window has passed, and it means water is still actively moving through the wall from an outside source rather than from the original construction moisture. The two look identical on the wall. The difference is entirely in the timing and whether it keeps recurring.

Why it is worst on new construction

Fresh masonry holds a great deal of construction moisture and has its full original salt content still near the surface. New brick and block commonly bloom heavily through their first year or two and then taper off as the available salts are depleted. On a new build this is normal primary efflorescence rather than a defect, which is worth knowing before anyone alarms you about it.

Persistent efflorescence means water is getting in

If a wall keeps blooming years after construction, that is secondary efflorescence, and water is still moving through it from somewhere. That points at a failed flashing, a downspout discharging against the wall, splash-back from grade, or a gutter overflowing onto the masonry. Cleaning the bloom without finding the water source is treating a symptom that will simply reappear.

What removal can and cannot do

The surface deposit can be removed properly, typically with a masonry-appropriate cleaner and rinsing rather than aggressive scrubbing. What cleaning cannot do is stop it returning while water is still traveling through the wall, and aggressive acid washing can damage the mortar face and actually increase its porosity, making future blooming worse rather than better. We will tell you when what you need is a drainage fix rather than another wash.