QUESTIONHow do you remove efflorescence from terra cotta tile that extends under the front door. Inside the tile was covered with laminate flooring 25 years ago. This problem just started last year. Is there something I can coat it with to prevent it from coming back.
ANSWERANSWER - Severe efflorescence is a symptom of an excessive moisture problem. Removing the efflorescence stain is treating the symptom rather than the problem.
Efflorescence is a mineral stain. Minerals are forms of salts that dissolve in water. The underlying moisture under the Terra Cotta tile migrates to the surface of porous tiles to evaporate. As the moisture evaporates it precipitates the minerals that can cause spalling (tile surface degradation) from the expansion of the minerals. The precipitated minerals causes the staining.
If the staining is typical white calcium material it can be easily cleaned up with water and a tile cleaner for removing efflorescence. The cleaners a mild diluted acids, so it is better to use a store bought product for removing the efflorescence staining.
If you are not fixing the excessive moisture problem, then the condition will reoccur. You can try to apply a penetrating sealer over the tile to try to minimize the staining, and make it easier to clean, but it won't prevent the staining.