Protecting Your Walls by Barbara Jennings
Efflorescence Ruining Your Walls?
If you have brick, masonry, stucco or concrete walls you may be susceptible to a common problem called efflorescence. Efflorescence causes
peeling, spalling, shaling and white stains. These types of walls contain soluble salts. When these salts are dissolved by water, which is a bigger problem in places that
get a lot of rain, snow or just a lot of moisture in general, the salts will be carried to the surface, remaining there while the water evaporates. The crystallized salt left on the
surface of the wall will, over time, erode the surface of the wall.
A crystalline deposit is left on surfaces of masonry, stucco or
concrete. Whitish in appearance, it is sometimes called "whiskers" and it can flake off and make a room feel dusty - not good for your health.
How Efflorescence Forms
It is no mystery as to how the salt deposits migrate and form. They can originate in many different sources with moisture as they are water
solluable salts. Initially water must be present to dissolve and transport the salts. All the water needs is to find channels, even microscopic ones, through which
the water and the dissolved salts can travel.
Denser materials such as brick, stone, stucco or concrete make it more difficult for this to happen, but they are vulnerable to the migration
of salt never-the-less. The most likely surfaces for efflorescence are less dense surfaces.
As the water carries the salt to the surface, it eventually evaporates, leaving the salt behind. The water can even evaporate before it reaches the surface, thus
leaving salt behind below the surface where it is unseen. This eventually causes something appearing like "whiskers" to project outward, even as much as a half inch beyond the
surface of the wall. On such surfaces as stucco and painted walls, the efflorescence appears as spalling and peeling.
A Cycle of the Seasons
Efflorescence is generally a seasonal problem because it is directly affected by the level of humidity.
It's intensity increased during and after the rainy season. Spalling and peeling are usually noticeable during the dry periods of spring and summer. Left alone the cycle will
no doubt repeat for months or even years. The nature of the salts and the amount deposited varies depending on the character and source of the soluable salts.
The Composition of Efflorescence
For more than 100 years, efflorescence has been reported and studied. It is generally accepted that it originates from more than one source
and may include more than one or two compounds. In a bulletin by T. Richie, issued by the Division of Building Research of the
National Research Council, Ottawa, Canada, it states, "the following compounds are
found in efflorescence"
- Sodium sulfate
- Potassium sulfate
- Sodium carbonate
- Calcium sulfate
- Sodium bicarbonate
- Calcium carbonate
- Sodium silicate
- Magnesium sulfate
Go to Part II
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