How to Prevent Gas Bubbles in Epoxy Resin

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Epoxy resins are used to finish tables, bars, furniture and more. These finishes are extremely durable, and when properly applied provide a seamless and waterproof glass-like finish. Avoiding blemishes in the finish--like bubbles--requires careful preparation of the surface and attention to detail when mixing the resin with the hardener. There are two major sources of bubbles in epoxy finishes: air bubbles can be introduced when the resin is being mixed, and can also form if the epoxy reacts with the surface on which it is applied.

Things You'll Need

  • Epoxy resin
  • Hardener or catalyst
  • Stirring stick
  • Mixing container
  • Brush
  • Low intensity flame or CO2 source
  • Drill
  • Clean the surface carefully; use a cleaning solvent or detergent suggested by the manufacturer. Solvents must be completely dried out of the surface you are going to coat or they will degas as you apply the resin and cause bubbles.

  • Mix the resin and the catalyst (hardener). For large jobs, use a paint can or other container. Use a paint stir stick to gently fold the catalyst into the resin. It is critical that you don't allow any air into the mixture or it will form bubbles. Use an epoxy with a longer working time to allow you to mix it slowly, carefully and thoroughly without injecting any air.

  • Apply the resin. You can pour epoxy resin over large areas. Most manufacturers suggest coats no deeper than 1/8 inch at a time. You can also brush on epoxy resin--this is usually easier than pouring. Make sure the brush is thoroughly wetted with the resin or air bubbles can form in the brush and become introduced into the epoxy.

  • Examine for bubbles. If you see tiny bubbles while the resin is still wet, you might be able to get them out with CO2 or a heat source. Use a low-intensity flame like a cigarette lighter or alcohol burner and pass the flame lightly above the area with the bubble. Do not attempt to heat the epoxy--it can catch fire. The CO2 in the flame should draw out smaller bubbles. Make sure that your brand of resin is not flammable and that the manufacturer suggests the flame treatment for bubbles before proceeding. Some manufacturers suggest not using a heat source because it can leave waves in the surface. Instead, try breathing or blowing gently on the areas that have bubbles.

  • Pop larger bubbles. If you have a large air bubble, use a pin or needle to get the air out. Do this well before the resin starts to set or it can mar the finish. Push the pin or needle into the bubble, then wobble the pin back and forth to allow the bubble to reach the surface--it should vent out and the bubble will disappear as it fills with resin.

  • Use a drill to remove bubbles after the epoxy has hardened. Apply a second coat of resin to get a glassy, seamless finish. A very thin final coat is less likely to have bubbles. If bubbles remain in the final finish, they are easier to remove using the CO2 method.

Tips & Warnings

  • Thinner coats and thinner epoxies are less likely to get trapped bubbles. You can thin epoxy resins with a variety of solvents--check with the manufacturer for suggested thinners. Make sure the working time (time before the epoxy hardens) is sufficient to allow you to work on any bubbles that might form after you apply the resin.
  • Don't apply epoxy finishes in direct sunlight--this will almost guarantee out-gassing and bubbling.
  • Uncured epoxy resin and catalyst are toxic. Handle with appropriate protective clothing and safety equipment.
  • Epoxy generates heat as it cures. Never allow a large container of epoxy to cure solid--it can catch fire or explode. Check with the manufacturer for the maximum volume of epoxy that can be cured safely.
  • Make absolutely sure the manufacturer suggests using the flame method for getting rid of bubbles. Uncured epoxies can be flammable. If you use a thinner that is flammable--do not use the flame method.
  • Always use epoxy resins and thinners in well ventilated areas.

References

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