Efflorescence is a white crystalline deposit composed of salts, lime and/or other minerals. These deposits may become visible on many types of building product surfaces such as concrete, stucco, grout, masonry, brick, natural stone, clay, ceramic and even wood. These salts and minerals are water-soluble and generally come from the ground or where cementitious or alkali substances exist. These salts and minerals travel to the surface, using moisture as their carrier, where exposure to air evaporates the moisture leaving behind salts and minerals on the surface.
These salts and minerals are generally channeled by water as they travel through concrete substrates. This process is called capillarity. Capillarity is best explained as the movement or transmission of water or moisture in masonry. By definition, it’s the action by which the surface of a liquid, where it comes in contact with a solid, rises or falls. This attraction or repulsion is caused by capillary action. Because of this behavior, moisture may travel to lower or higher levels within a material and can move in many directions.
Efflorescence can be found on the oldest of installations but will frequently be created after a new tile or natural stone installation. This may be due to the capillarity process if the stone or tile is installed on a concrete substrate or may be moisture originating from the setting material (e.g., thinset, mortar) if mixed with water that then travels through to the surface. Sometimes alkali surfaces, like many limestones or grout, may be the source of salts and minerals. In all cases the salts and minerals need water or moisture as the carrier to bring them to the exposed surface level. In situations where a fat mud setting mixture is used (when additional lime is added to the mortar) there may be an increase in the efflorescence problem.
The moisture transmission will follow the path of least resistance. Therefore with dense surfaces such as ceramic tile, it is often found that the grout lines are more vulnerable to show efflorescence due to the higher concentrations of these deposits. On the other hand, the saltillo or terracotta paver is porous enough that the moisture transmission and salt or mineral deposits can be noted throughout the entire surface.
On nearly a daily basis, we hear the cry for help regarding efflorescence. The usual comment sounds like, “I have a white powdery haze on my surface and I have used every cleaner under the sun to no avail. These cleaners appear to be working when my surface is wet, but when the surface becomes dry it comes right back, leaving me with false hopes. What can I do?”
Some solutions to consider prior to a new tile installation would be to use a waterproof membrane beneath the installed surface. This helps minimize or eliminate efflorescence-causing salts and minerals from rising from below. This isn’t a foolproof solution as you are still vulnerable to exterior elements such as rainwater, sprinklers and moisture from the air penetrating your surface moving down to the cementitious adhesives below. In this last scenario, the moisture transmission begins again, which may lead to efflorescence occurring on your surface. This can be minimized or eliminated by applying a good, breathable penetrating water repellent to your surface. Actually, many good water repellents can help efflorescence from occurring when the original source of moisture is coming from the exterior elements or from below.
If efflorescence exists on an existing surface, the best method of cleaning or removing it would be to use an acidic cleaner. These salts and minerals are reactive to most acidic cleaners and will usually dissolve upon contact. This remedy also has some problems because with acidic cleaners you often have to use acids that aren’t so user friendly and may be dangerous for human use. The less dangerous acid products are often not strong enough to solve the tough problems. The good news is that new molecular science has recently created safe alternatives without compromising the product strength.
Occasionally, the efflorescence cleaning and removal process can become more difficult if latex or chemical transmission occurs at the same time as the salts and minerals transmute. These latex or comparable chemicals are often found in the more modern and advanced cementitious adhesives and grouts being used. The latex acts as a protective barrier around the efflorescence and defends the deposits from direct contact with acidic cleaning products. To help solve this problem, select an acidic product that has cleaning agents in it (acid and cleaner in one single product). Another recommendation would be to use a high alkaline restoration cleaner to break down the latex protective coating, rinse well and then proceed with the acidic cleaning.
A word of caution: Some natural stone products and other surfaces may adversely react to acidic products and using an acidic cleaner may cause problems. These problems may include the etching of a stone’s polish, opening the face of some surfaces creating a more porous surface, thereby causing other problems such as dirt and dry soiling issues. Please consult with an expert prior to using acidic products on any natural stone surfaces. There are other non-acidic solutions that can be used in such cases.