What Causes Bubbles in Epoxy Coatings?

Key Points:

• Bubbles are usually caused by air, moisture, or improper application
• Surface prep plays a major role in preventing defects
• Temperature and mixing technique directly affect results
• Most bubbling issues can be avoided with the right process

Have you ever finished an epoxy coating only to see tiny bubbles forming on the surface?

It can be frustrating especially when everything looked perfect during application.

So what actually causes bubbles in epoxy coatings?

The short answer: air, moisture, or improper technique getting trapped during the curing process.

Most bubbles are not random they are a sign that something in the process needs attention.

1. Air Trapped in the Concrete

Concrete is naturally porous and contains tiny air pockets.

When epoxy is applied, these air pockets release gas upward, creating bubbles.

• More common in older or unsealed concrete
• Happens during early curing stages
• Often visible as small pinholes or clusters

2. Moisture in the Surface

Moisture is one of the most common causes of bubbling.

Water vapor rises through the slab and disrupts the coating.

• Can come from the ground below the concrete
• May be present even if the surface looks dry
• Often causes recurring or widespread bubbles

3. Improper Mixing Technique

Mixing epoxy too aggressively can introduce air into the product.

That trapped air gets released during curing.

• Fast mixing creates micro air bubbles
• Using the wrong tools can increase aeration
• Not allowing epoxy to settle before use adds risk

4. Applying Epoxy Too Thick

Thick coatings can trap air and slow down the release of gases.

This makes bubbles more noticeable on the surface.

• Heavy application prevents proper leveling
• Increases chances of uneven curing
• Can lead to surface imperfections

5. Temperature and Environmental Factors

Temperature changes affect how epoxy behaves.

Warm surfaces can cause air expansion, while cold temperatures slow curing.

• Hot concrete releases more air
• Direct sunlight can trigger bubbling
• Cold environments may trap gases longer

Ideal conditions help epoxy level properly and release trapped air before curing.

How to Minimize Bubbles

• Prepare the surface thoroughly (clean, dry, and properly profiled)
• Apply primer to seal porous concrete
• Mix slowly and evenly to reduce air introduction
• Apply thin, controlled coats instead of thick layers
• Work within recommended temperature conditions

FAQs

• Are bubbles in epoxy permanent?
  Some minor bubbles can be sanded and recoated. Severe cases may require refinishing.
• Can bubbles appear after the epoxy has cured?
  Most bubbles form during curing, but underlying issues like moisture can cause delayed problems.
• Is bubbling more common in DIY applications?
  It can happen in both DIY and professional work, but preparation and technique make a big difference.
• Does primer really help prevent bubbles?
  Yes. Primer helps seal the surface and reduces air release from the concrete.
• Can temperature alone cause bubbles?
  Temperature contributes, but it usually works together with other factors like air and moisture.
• Where can I find epoxy systems and tools?
  You can explore epoxy coating solutions at PowerCoat Canada.

Epoxy coatings are sensitive to small details, and bubbles are often the result of overlooked steps.

Understanding the causes helps you avoid common issues and achieve a smoother finish.

Looking for better results on your next coating project? Check out professional-grade epoxy products at PowerCoat Canada.