Bubbles are the most common complaint with clear epoxy pours and tabletop coatings. Most of them come from four sources, and each has a simple fix.
Where bubbles come from
- Mixing. Whipping the resin folds air in.
- Cold, thick resin. Cold epoxy is more viscous, so trapped air can’t rise and escape.
- Porous surfaces. Wood, concrete and cork release air as the epoxy soaks in. This is called outgassing. It’s especially bad when the surface warms up during cure.
- Pouring too thick for the product. Deep pours of a coating resin can trap air and overheat.
Prevention
- Warm the resin and hardener to room temperature before mixing. Warmer epoxy flows better and releases air more easily. Warm it too much, though, and pot life gets shorter.
- Mix slowly and thoroughly. Scrape the sides and bottom. Don’t whip.
- Seal porous surfaces first with a thin seal coat, and let it set before the flood coat.
- Apply when the temperature is steady or falling (late afternoon rather than morning), so the substrate isn’t warming and pushing air out as the epoxy cures.
- Use the right product for the depth. Deep-pour resins are made for thick castings. Coating resins are not.
Removing bubbles while it’s wet
A quick, sweeping pass with a heat gun or propane torch lowers the viscosity at the surface and pops the bubbles. Keep it moving. Lingering can scorch or ripple the surface, and flame near solvents is a fire hazard. Follow the product’s instructions.
Fixing bubbles after cure
Sand the area flat, clean it, and apply another coat. If you’re recoating after the first coat has cured, check for amine blush first (see amine blush).
Manufacturers’ application guides, such as the WEST SYSTEM instruction manuals, cover temperature and recoat windows for each product. Related: curing epoxy in cold weather ยท epoxy calculator