Masonry or plaster with white-ish crystallization is called efflorescence.
Efflorescence is primarily an appearance problem that occurs with masonry and often plaster. Rarely do these deposits of crystalline salts do any harm to masonry surfaces. In most cases, the efflorescence appears as a white dust or deposit on the surface of brick walls, chimneys, or patio bricks. In certain cases, the color of these salts can also be green and brown.
3 ingredients are needed for efflorescence to form.
Efflorescence requires three primary ingredients in order to occur: Availability of water soluble salts, a source of moisture or water to dissolve and transmit the salts, and an environment where the moisture can readily evaporate, thereby depositing the dissolved salts.
Sources of the salts.
The efflorescence deposits that you see on your brick or masonry can come from many sources. This, of course, often makes it a little tougher to control the problem. The salts can reside in the masonry units (brick, block, etc.), or they may be present in the mortar or cement, the water used to mix the mortar, sand, rain or ground water, soil and backfill dirt, etc.
Efflorescence is not always easy to control. Often it is very difficult to locate the source of moisture or water which is dissolving the salts. Efflorescence on exterior masonry might simply be a result of rain water which soaks into the masonry surface or ground water which is being wicked from the soil into the masonry.
Rain water is often considered to be the primary moisture source for most efflorescence problems. Most masonry will absorb rain water. If a masonry job is improperly constructed, massive amounts of water can be absorbed.
How does it happen?
For sake of this discussion, let’s say that the source of the salts that cause efflorescence are within the masonry bricks. Here is what happens: When the bricks are laid, the bricks absorb moisture from the wet mortar. In certain instances, the bricks may get wet during construction from rain or snow.
Water has a tremendous ability to dissolve things. It can dissolve sugar, salt, medications, soaps, instant iced tea, Kool-Aid, etc. It should come as no surprise that it can dissolve the ‘salts’ in a brick.
When water enters the brick in our example from any direction (top, bottom, sides, front or back) it begins to dissolve the salts. The salts are now in the ‘solution’ created by the water and travel along with the water. As happens with most brick surfaces, they eventually see a sunny, breezy day. This is the final element needed to deposit the salts on the surface of our example brick. What actually happens is quite simple. The sun and wind evaporate the water from the brick. However, only the water makes it into the air. The salts are left behind at the surface.
Efflorescence on interior plaster work can be a sign that a major problem is beginning to develop. So you should not ignore it.
Water of course is a primary ingredient in the mechanism of efflorescence. As such, efflorescence on interior plaster surfaces generally indicates that water is either leaking within or into a structure. Most of us do not want water to travel freely through the inside of our structures. The source of this water should be identified and corrected before major structural damage is allowed to occur.
Control of efflorescence.
Efflorescence is very difficult to control, especially outside. For the most part, the control of efflorescence depends upon the elimination of one of the three mechanisms which causes efflorescence. As long as there is a limited amount of soluble salts located within the masonry, soil, ground water, mortar, or plaster, the condition will stop only after the supply of salts is exhausted.
If you choose not to wait for this to occur, then you must identify and stop the source of moisture which is dissolving and transmitting the salts to the surface. It is important to note, that even after control has occurred, the efflorescence may continue for a short period because of the presence of residual moisture within the masonry, mortar, backup masonry, backfill, etc. Do not become alarmed if the salts continue to come to the surface for a short period of time.
Efflorescence can be cleaned using several methods. Usually, it is best to simply brush the salt deposits off the surface with a stiff broom. The use of water is not always recommended. The water can dissolve some of the salts and actually drive them back into the masonry. They will subsequently re-appear when this secondary water evaporates. In the most severe cases, dilute solutions of muriatic acid can be used. However, BEWARE of this method. Muriatic acid can cause serious eye and skin burns. The vapors are also very toxic. Muriatic acid, improperly applied to a masonry surface, can ‘burn’ the brick and cause discoloration.
Sealing brick not always the best idea.
Brick that is still experiencing efflorescence should not be sealed. If you do this, there is a possibility that you can actually damage the surface of the brick. The sealer can actually block the movement of salts to the surface of the brick. Now you may think that that is not such a bad idea. Well, here is what can happen:
The salts work their way to the sealer at the surface of the brick and stop. The concentration of the salts increases as the water evaporates. In certain instances, the salts begin to crystallize. This process of crystallization can create enormous pressures on a microscopic level that can actually cause the face of the brick to pop off or spall.
Bob Beisbier, owner of BK Home Inspections, is a Certified Master Home Inspector who has been providing professional and thorough home inspections in southeast Wisconsin for over 12 years. Bob is Infrared certified, DILHR Certified, and provides Home Energy Tune-ups, Environmental Data Reports, Pre-sale Home Inspections and Pre-offer Home Inspections.