Efflorescence is a term used in chemistry to describe the migration of a salt to the surface of a porous material, where it forms a coating. The process involves the dissolving of an internally held salt in water or another solvent. Efflorescence can occur in natural and built environments and may present a cosmetic outer problem only, but can sometimes indicate internal structural weakness. It can be a crystalline deposit of salts that can form when water is present in or on brick, concrete, stone, stucco, or other building surfaces. Efflorescence is not dangerous, but it can lead to moisture problems causing structural damage to building materials.

Efflorescence can be a white, powdery substance that can be found on unsealed surfaces. It can vary in frequency and intensity throughout the country due to moisture and temperature. Three conditions need to exist for efflorescence to occur: there are water-soluble salts in or on the material, moisture is present to make the salt become a soluble solution, and as salts move to the material’s surface, the moisture evaporates. This makes the salts crystallize, which results in efflorescence.

Efflorescence can be prevented with capillary breaks, such as by installing a polyethylene sheeting under a concrete slab. Hydrophobic sealants can also be used to prevent the absorption of water or water from traveling within the material. When efflorescence does occur, it’s important to troubleshoot and know what to assess to help determine the possible reason behind it.