Repair air bubbles and craters in epoxy and polyurethane floors

Air bubbles and craters in newly installed concrete floor coatings often come from gases flowing through porous cement.


Air bubbles and craters in newly installed concrete floor coatings often come from gases flowing through porous cement. These gases can be argon, methane, or whatever is under the plate. Sometimes the gas comes from chemical reactions that are still produced during the preparatory floor cleaning process. Typically, these gases come from air drawn into the room by a heating system or natural airflow. We describe here a simple, effective solution to fix these flaws.

Many times, simply sifting the Walk-behind Scrubbing Machine and putting on another coat will do the trick, but not always. That said, even after the second coat, there may be signs of blistering. Look closely at one of the bubbles, remove any skin, and see if there is a small hole in the bottom of the crater. This small hole indicates that something was blown through the hole, causing the bubbles. For an aggressive treatment, fill each hole with a polish before the next coat. While this may sound like a lot of work, a 1,200-square-foot floor can actually be done by you and an assistant in about an hour.

Here are the steps to proactively fix and hide crater issues. First, use a rotary scrubber with a 60-grit screen and drive pad to quickly sweep across the floor, scraping off the tops of any air bubbles, thereby leveling the floor. Next, sweep and filter dust. Then put on these knee pads, use a toothpaste-style tube of glazing compound and a putty knife, and start filling. After all the problem pits are filled, screen again. Once the filling is done, a good second screening can be done immediately. This sifting will quickly remove excess glaze and blend each hole evenly. Sweep again, then apply to the floor.

With this extra hour of work, you can ensure that all holes are permanently filled and that there are no remaining holes in the floor, and there should be no new air bubbles or craters. Make sure not to stir air into the mixture when mixing the floor paint. I use the hand paddle for about 200 strokes, then let the mixture sit for 20 minutes before using, if the pot life allows. If you suspect your roller cover is pushing air into your product, use a mohair-type roller cover and pour the product on the floor; do not submerge the roller in it. It is also helpful to keep the room temperature close to 70 degrees and prevent wind and hot or cold spots.