When working with epoxy resin, bubbles are one of the biggest (and most annoying!) issues that can arise. They can appear as a result of many factors such as not following epoxy best practices, working in suboptimal temperatures, or mixing incorrectly. But do not despair! Let’s see how to prevent bubbles in resin and how to fix them if they’ve already popped up.
What do bubbles indicate?
If bubbles arise in your epoxy project, this indicates one simple thing: trapped air from beneath the surface is being released. Even though they are commonly referred to as “bubbles”, this process is actually called “outgassing”.
What causes bubbles in epoxy resin?
Bubbles often appear following a freshly applied epoxy coat. There are a number of factors that can affect the outcome of your project. The most common ones include not following best practices when working with resin, cold temperatures, and pouring epoxy that’s too thick. However, there are times when it seems like you’ve followed every rule in the book and yet the piece you are working on still releases trapped air.
The good news is that it happens even to the best of us - and it’s totally fixable!
How do you prevent epoxy bubbles?
Choose quality resin for your project
It all starts with choosing the perfect epoxy resin for the DIY project. Whereas, with some brands, micro bubbles in resin are avoidable due to their texture, others just need to be applied in thinner layers to achieve fewer bubbles.
Depending on the project you want to resin, Roxy Epoxy offers a 16 oz resin kit (perfect for jewelry, coasters, tumblers, and more) and a 2Q resin kit (suitable for woodworking, flooring, table tops, or bar projects).
Warm your resin before casting
Another trick to prevent bubbles is to heat the resin before casting. The best way to do this is to put both bottles in hot water for 30-35 minutes at a temperature of 122°F (50°C) before mixing. This helps the resin mix nicely. After the contents of the bottles have warmed up completely, place them aside until they have returned to room temperature.
Please handle hot water with caution and do not bring water to a boil (212°F/100°C).
Be careful when mixing
Bubbles can also arise during the mixing process, prior to applying the epoxy coat. This is why it is important to thoroughly mix the components before applying the coat. Another important aspect to be aware of when mixing the resin with the hardener is the type of stick you’ll be using to mix. It is best to use an object that does not have crevices so as to not disrupt the continuity of the blend.
How to mix epoxy resin without bubbles the right way? Thoroughly mix the two components with clean stir sticks until the mixture becomes transparent. Depending on the quantity you’re mixing, it can take between 3 and 7 minutes of continuous mixing without whipping.
Make sure to properly prepare the surface you are pouring the resin on
Applying epoxy successfully also depends on ensuring that the epoxy adheres well to the surface. Follow these 3 simple steps to prepare the perfect surface for your epoxy:
- Clean the surface first by using a solvent to remove contaminants. Solvents that may help with this process include IPA, toluene, xylene or mineral spirits. Wipe the surface with paper towels before the solvent dries.
- All epoxy bonding surfaces must be as dry as possible for good adhesion. Speed up the process by using a heat source (hot air gun, hairdryer, heat lamp) or a fan.
- Before applying epoxy, thoroughly abrade the surface. Sanding and polishing are the cornerstone for a perfect surface. For more information about sanding and polishing, read this article.
Dust baby powder on the surface
Here’s a useful trick! When casting resin, use a small amount of talc/baby powder to get rid of bubbles in resin. Sprinkling baby powder and warming the silicone rubber mold can decrease the surface tension, reducing air bubbles. Use a delicate paintbrush to dust in the powder and then tap out any excess powder.
Try to ‘demold' the resin several times during pouring
For intricate molds, pour some resin into the mold, then pick it up and twist it as if you were going to demold it. This allows trapped air bubbles to rise to the surface.
Dip inclusions in resin before putting them into your mold
This is also done to break tension in the surface. Putting inclusions flat onto a resin surface will likely trap bubbles underneath. Once you have dipped them into the resin, put them into your mold at an angle, then move them into place.
Use a heat source to pop bubbles before drying
To pop bubbles, go over your project with a heat source one final time.
After you’ve poured the resin, wait about 10 – 15 minutes and then use a propane or butane torch. Hold it 6-8 inches above the surface. This helps thin out the resin, bringing the bubbles to the surface and popping them. Depending on the depth of the resin pour, you can repeat this method throughout the curing process.
For a beginner or part-time hobbyist, you can also use a hairdryer as explained above.
Use a pressure pot
With some types of resin and for large castings, the only way you can get rid of bubbles is to use a pressure pot. A pressure pot uses pressure to force air out of resin and into thinner sections of a mold. This helps you eliminate air bubbles in cured castings.
Can you fix air bubbles in cured resin?
Yes, you can. If bubbles are present in a cured piece, you will need to sand down the surface and apply a second coat. You can also use a razor blade to pop the bubbles, which will create an open cavity. Mix a small amount of epoxy to fill in those holes. Let it cure for 5-6 hours, then re-flood the surface.
Once you understand the elements of a successful resin project, you can retrace your steps and see what went wrong whenever issues arise. Here are some additional tips on how to prevent bubbles in resin:
- Use a non-porous stirring stick to stir your epoxy.
- Stir the epoxy without whipping or lifting.
- Avoid grease, oil, wax, and any other foreign components as they can leave an irregular texture on the surface.
- To remove small bubbles while the resin is wet, apply heat directly above the bubbles.
- Do not allow the epoxy to sit in the mixing cup any longer than it needs to as it can cure improperly.
Even simple beginner resin projects can go wrong if you don’t follow instructions accurately. There are a lot of variables at play, but we hope our tips on preventing and getting bubbles out of resin will come in handy in the future.