Efflorescence is a surprisingly complicated phenomenon that has existing in our built environment for thousands of years. On the surface of it, efflorescence is simply water traveling through a material, such as masonry, dissolving alkalis which solidify again once the water evaporates. When evaporation happens at or near the surface of a material the alkalis are revealed as a white powder. (Note: Not all white residue on buildings is a result of this type of efflorescence. This is simply a common kind.)
After a flood in our basement, efflorescence appeared on the concrete and I shall use it to explain investigative and remedial processes. In most cases when one comes across efflorescence it is without previous knowledge of the source of water. The first step is always to try and figure out the path of travel of the water. This is not necessarily easy and writing out a list of possibilities is always a good idea. Although the flood in my basement covered a large part of the floor, efflorescence only appeared in one area. It is important to remember that efflorescence can only occur when alkalis have been dissolved into the water. You can still have a major water problem without efflorescence being the result.
Determining the source of the alkalis may help find the source of water. These "salts" can come from Portland cement, sand, soil, within a brick, or from the water itself; usually from a combination of sources. If the water that flooded my basement had alkalis in it, then most of the flooded region would have revealed efflorescence. In the same way if the alkalis had come from the concrete mix, then I would have seen more affected areas. Instead efflorescence was located along a crack in the floor. It is pretty clear that the salts came from the ground below the concrete that has been brought closer to the surface through the crack.
Once the source of the water has been remedied the efflorescence can be removed... To be continued!
