You apply your epoxy coating, expecting a smooth, flawless surface. Instead, tiny bubbles start to appear. Some are small, others more noticeable, and now the finish doesn’t look as perfect as it should.
This is a common issue. Epoxy bubbles happen when air or gas gets trapped under the surface and rises as the coating dries. The usual suspects? Air escaping from the concrete, improper mixing, temperature issues, or applying the epoxy too thickly.
Luckily, these bubbles can be fixed and, more importantly, prevented. Here’s what causes them, how to remove them, and what you can do to keep them from forming in the first place.
Concrete looks solid, but it’s actually filled with tiny pores. These pores trap air and moisture. When you apply epoxy, especially in warm or fluctuating temperatures, the air inside expands and pushes upward, forming bubbles.
This issue is more common with outdoor concrete since it’s exposed to heat, cold, and moisture changes. If the surface isn’t properly prepped, it’s almost guaranteed to cause bubbling.
Epoxy needs to be mixed thoroughly, but stirring too fast introduces air into the mixture. If those tiny air pockets don’t escape before the epoxy is applied, they rise up as the floor cures, creating an uneven finish.
Temperature plays a huge role in how epoxy behaves.
Too hot → The epoxy cures too quickly, trapping air bubbles before they can rise and escape.
Too cold → The epoxy thickens, making it harder for air to escape, which leads to bubbling.
For outdoor surfaces, it’s best to apply epoxy when the temperature is stable, not during the hottest or coldest parts of the day.
A thick layer might seem like a good way to get a strong finish, but it actually traps air underneath.
Thin layers allow air bubbles to escape more easily before the epoxy hardens, leading to a smoother and more even surface.
Outgassing happens when air or gas is released from the surface while the epoxy is curing. If the concrete hasn’t been sealed properly, these gases rise through the epoxy, leaving bubbles behind.
If bubbles have already formed, you don’t necessarily need to start over. The best way to fix them depends on how severe they are.
For small bubbles, lightly sand the surface, clean off the dust, and apply a thin coat of epoxy to smooth things out.
If bubbles appear while the epoxy is still wet, a heat gun or torch can help pop them before the surface cures. This method works best for smaller air pockets, but be careful—too much heat can burn or discolour the epoxy.
For larger bubbles that have hardened, drill a small hole into the bubble and fill it with fresh epoxy. This method helps even out the surface without having to redo the entire floor.
If bubbles are widespread and severe, the best fix might be to scrape off the affected layer and start fresh. This is time-consuming, but it guarantees a smoother finish.
Bubbles are easier to prevent than fix. Here’s what you can do before and during application to avoid them altogether.
Moisture in the concrete almost always leads to bubbles. If it has rained recently, or if the surface still feels damp, wait before applying epoxy. Applying a moisture meter can help confirm that the surface is dry enough.
A primer acts as a barrier between the concrete and epoxy, preventing air from escaping and reducing the chances of bubbling. It also helps the epoxy adhere better, leading to a stronger and more even finish.
Stir epoxy slowly and evenly to avoid trapping air.
Let the mixture sit for a few minutes before application. This allows any trapped air to rise and escape before it’s applied to the surface.
Applying a thick layer traps air, while a thin layer allows bubbles to escape before the epoxy hardens. If you need extra durability, applying multiple thin layers works better than one thick coat.
A roller spreads epoxy more evenly and reduces the chances of trapped air. Brushes can leave streaks and sometimes introduce bubbles. Using a notched squeegee is another great option for ensuring an even spread.
At Express Epoxy Flooring, we focus on outdoor concrete surfaces and garages—not wet areas or decorative finishes.
We offer epoxy coatings to create a durable and visually appealing surface. While we don’t provide finishes like stamped concrete or polished epoxy, we can apply coatings over existing concrete to refresh the look and extend the lifespan of your surface.
Our process prioritises proper preparation and careful application, minimising common issues like bubbling while ensuring a long-lasting, even finish.
