Where does efflorescence come from and how do you remove it?
I spoke to a customer about white stains on their stonewall. After reviewing the construction procedures and pictures, we determined that the stains were caused from efflorescence. Efflorescence is present when water-soluble salts are allowed to travel to the surface where the water evaporates, leaving the salts behind. They can be in the form of white powdery stains or if allowed to build up on the surface the salts will create a "crystalline" efflorescence.
Both of these problems can be removed. The white powdery stain can be removed a lot easier than the crystalline. To remove the white stains try cleaning with clean water and a stiff brush. If this doesn’t work then an efflorescence treatment cleaner will be needed.
I found a good website that has cleaning products for efflorescence. It is http://www.aldonchem.com/. Check out their Step 2 FAQ’s and Problem Solving section for advice and products to use to clean efflorescence from stone products. They have a product for both the powdery white stains and the crystalline stains.
Crystalline stains will require more work than cleaning with water. This is because the salts have been allowed to build up and have created crystals on the surface. When using a cleaning agent to remove the crystals here are a few tips:
- Don’t use strong pool acids or muriatic acid. A much safer hydrochloric acid mixed with cleaning agents is just as strong and much safer than muriatic acid.
- If you hear a “fizzing” sound when cleaning, then it is efflorescence. If not it is another problem.
- Although hydrochloric acid is safe, it is recommended to not let it contact any vegetation.
When all of the crystals have been removed you may need to clean the surface with a cleaning agent that removes the white powdery stains. Check out the above website for both of these products.
If these products do not remove the white stain, then the problem is not efflorescence. It could be mineral deposits that have come in contact with the stone from the outside. These deposits will need other cleaning agents, but similar to efflorescence can be removed from the surface of the stone.
When the stains have been removed the stone can be protected from future efflorescence by sealing the stone with a penetrating sealer.
This step-by-step procedure should take care of most efflorescence problems. If problems persist and you are convinced that efflorescence is the problem, contact the manufacturer for more details on how to deal with the stains.
Let me know how these steps work for you. If you take some before and after pictures you can send them to me at firstname.lastname@example.org. I’ll include them in my design center so that they may be helpful to others in the future.