How to Remove Efflorescence: Tips and Tricks
Efflorescence is a common problem that can occur when casting concrete. It appears as a white, powdery substance on the surface and is commonly caused by the migration of salt deposits from within the material. This nasty residue is purely cosmetic and it is not a structural problem. If left untreated, however, it can make finishing your art a challenge.
Follow along as we share our process of removing this pesky film and if you are having issues with Air Bubbles, check out this post for some tips.
Removing Efflorescence Step by Step
Step 1: Be Sure to Fully Cure the Concrete Cast
Efflorescence is caused by the migration of salt deposits to the surface of the concrete. Remove the casted item from the mold. Moisture will draw outward and the film will be left behind. Let the concrete fully dry/cure before moving to the next step. Also if you need help understanding how to cast concrete, check out our blog post showing you how to prepare and cast concrete from molds.
Step 2: Wet the Surface
Once fully cured, outside of the mold, the surface needs to be wetted thoroughly with clean water. This will help to dissolve the salt deposits and prevent them from resettling on the surface.
Step 3: Use a DIY Efflorescence Solution or Store Bought
DIY Vinegar and water solution—Blend household white vinegar and water. Dilution ratio is 20–50% vinegar in water by volume.
Store Bought Solution - Indoor and Outdoor Safe and Non Toxic
Step 4: Scrub the Surface
Using a stiff-bristled brush, scrub the surface of the concrete or masonry to remove the efflorescence. Be sure to work in small sections, rinsing the surface frequently to prevent the cleaner from drying on the surface.
Step 5: Rinse the Surface
Once the efflorescence has been removed, the surface should be rinsed thoroughly with clean water to remove any remaining cleaner residue.
Step 6: Allow the Surface to Dry
Allow the surface to dry completely before applying any colorants, sealers or coatings.
Additional Tips for Removing Efflorescence
If efflorescence is particularly stubborn and as a last resort, you can use muriatic acid. We do not particularly enjoy working with this material, but it will zap the efflorescence.
Removing efflorescence from a concrete can be a challenging task, but with the right tools and techniques, it can be accomplished successfully. Remember to allow the concrete to fully cure outside of the molds, wet the surface before cleaning, apply an efflorescence cleaner, scrub the surface, rinse the surface, and allow it to dry completely before applying any sealers or coatings. By following these steps and using the right products, you can remove efflorescence. Dig in!