One reason acrylic concrete sealers bubble is the extremely porous nature of concrete. If an acrylic sealer is applied to an exterior application when temperatures are rising it is common for the expanding air to bubble in the sealer. Another common cause of concrete sealers bubbling is over application. When applying a solvent based acrylic sealer, the solvents in the sealer are supposed to distribute the acrylic evenly across a concrete surface, and then evaporate into the atmosphere leaving behind an acrylic film to protect the concrete. If the application of sealer is applied too heavily the solvents can become trapped under the acrylic film. They are unable to evaporate, resulting in solvent entrapment and bubbling. This is most common in high temperatures or when the sealer is applied within direct sunlight. It is best to apply a sealer is the morning or evening between 60-90 degrees F.
Another common problem of acrylic sealers is a milky or white appearance which is known as blushing. This is also caused by over application and the inability for the sealer to properly evaporate.
How to fix concrete blushing and bubbling?
By using a nap roller, a bristle broom and Xylene applied at a rate of 250 sq. ft. per gallon, roll the Xylene into the concrete and allow it to soak until the acrylic sealer is dissolved. After a minute or two the sealer will have melted and it will become soft. Use a roller to even out any surface bubbles and blushing. If the sealer was extremely over applied, use a bristle broom to carefully scrub at the acrylic; use a roller to roll out any broom mark patterns. Do not back roll when using the roller with Xylene.