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The 2026 MCAA Annual Online Auction ↗

Efflorescence: Efflorescence Questions and Answers

Words: Jeremy DouglasQ. I’ve been having a really difficult time lately getting rid of the efflorescence from my walls, starting about six months after the brick has been laid up. Is there any reason why I might be having such a hard time?

A. Without seeing exactly what you are experiencing, it’s hard to say what specifically is going on, but let’s start analyzing this issue from the beginning.

First, I feel it important to point out that not every white substance showing up on the face of a wall is efflorescence. Even in new construction, calcium deposits or lime run may also be the culprit, and is often mistaken for efflorescence. Sometimes the terms are used interchangeably, when in fact they are very different. It could well be that you are mistaking a calcium condition for common efflorescence, the calcium being much more difficult to remove.

The visible difference between the two is a direct comparison of their solubility. Efflorescence is a deposit of water-soluble salts that are actually driven through the masonry. Efflorescence presents on the wall face as a light, crystal-like powder, flaky to the touch and salty in taste. Because they are water-soluble salts, true efflorescence will disappear when wet.

Conversely, a calcium extrusion or lime run presents as a hard, crusty formation and is not soluble in water. Therefore, it remains visible even when wet. It is important to note that this calcium is going to be deposited from a water source that moves through a void, likely found in the mortar joint, such as a hairline crack where the brick and mortar interface each other. As the water flows and deposits the calcium over the same area again and again, the formation builds and becomes larger over time.

Efflorescence is almost inevitable in new construction, and most of the time will disappear on its own after the initial moisture sources have had an opportunity to dry and providing there is adequate ventilation in the wall cavity. One can use certain manufactured masonry cleaners to help alleviate the condition more quickly. However, I usually recommend against that because, during that process, we historically have had a tendency of driving more water to the wall, which may simply perpetuate the problem. Certain emulsions are manufactured to be sprayed over the efflorescence and left without rinsing, so they introduce less water to the brick surface if used correctly. All of these efflorescence cleaners are usually derived from a hydrochloric acid solution, so they must be used specifically as directed by the manufacturer.

Cleaning a series of calcium deposits is more difficult. Because of the hardness of the encrustation, it is more difficult for a wet solution to penetrate its crusty layer in order to soften the calcium for removal. A combination of multiple applications of a manufactured cleaner, as well as manually breaking the heavier encrustation apart, is usually required for the acids to complete their work. There are some acidic gels that may prove helpful in these scenarios, as they allow for a longer time on the calcium surface. Even so, I urge caution in working with anything acidic applied over long dwell times, and again recommend specifically following all manufacturer recommendations.

Simply put, if you’re cleaning something that is disappearing and returning later, you are dealing with efflorescence, and you must stop whatever the source of moisture is. If you are cleaning a white scaling condition that doesn’t go away no matter what you do, it is likely calcium, and you’re going to have to roll up your sleeves and apply a bit of elbow grease. Good luck.
About: Technical Talks
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