One of the most common issues that can come up when working with epoxy is the formation of air bubbles. They tend to appear during the flood coat phase and less commonly during the other coating phases. These are typically easy to remove, and in fact the epoxy process has a built-in step for handling them before moving on to the final curing phase of an epoxy project.
Still, sometimes there are more air bubbles than expected, or they may be missed during the steps in which you'd normally remove or prevent them entirely. When working on a major project like an epoxy countertop, this is much better avoided.
For this article, we'll be covering why they appear and what you can do to prevent them. We'll then go over common practice on how to handle them, and dealing with worst-case scenarios.
Why do air bubbles appear?
There are two common reasons; let's go over both.
1. The substrate material is porous.
A material that is porous is one that has numerous tiny holes and grooves within its structure. These tiny spaces normally hold small pockets of air (assuming the material is dry).
When you pour mixed epoxy resin such as our table top epoxy directly onto a porous surface like this, the epoxy will slowly seep into these grooves and holes, pushing the air out and filling in the space.
However, because epoxy is thick and viscous, the air will sometimes get trapped inside the resin before it can make it all the way through to the surface. This trapped air is what we call air bubbles.
When air bubbles form and aren't removed through the methods we'll soon explain, they will show up in your cured epoxy finish, usually just below the hardened surface. Obviously, that is detrimental to both the strength of the finish and the beauty of its appearance.
2. The epoxy components weren't mixed properly.
Table top epoxy and deep pour epoxy are initially stored in two separate component containers. Each type of epoxy has a hardener component and a resin component.
Both of these components must be mixed together right before being applied to the substrate of your project. When mixing, there are some small things that can go wrong and induce air bubbles pre-emptively into your epoxy resin mixture.
If you're mixing a batch that is less than a gallon, but you choose to use an electric drill with an appropriate mixing bit, you may end up pulling in air due to the low quantity of epoxy and the high speed and power of the drill, which is typically used at medium setting for proper batches to ensure a good blend.
It's also possible to lift the drill bit too high during mixing, which can likewise pull in air even if your batch size is adequately large—one gallon in most cases.
Similarly, when mixing epoxy resin, there will occasionally be some unblended residual components on the sides or bottom of your container. After you pour your batch out, if you attempt to scrape this residue to maximize usage, you'll likely cause bubbles and other blemishes to form.
This is because the residue is actually improperly blended resin that started curing too early in the mixing container and does not meet the proper blend ratio needed for a clean cure.
How do you prevent air bubbles?
Fortunately, preventing air bubbles is incredibly simple.
First, make sure you apply a seal coat when needed.
An epoxy seal coat is a painted on coat of epoxy that seals your surface area. It's very thin because of the amount used and the manual application method, and it is designed to seal in or release the subsurface air in your substrate. A thin amount of epoxy isn't enough to trap the air in, so it will have no problem releasing.
Even more, the seal coat will bond very well with any flood coats or deep pour coats your project calls for. Just make sure you follow the right timing for this, as described in the instructions provided with your epoxy.
A seal coat for non-marine purposes is always applied with table top epoxy; you wouldn't use the deep pour epoxy for this, as it isn't as effective for this method.
Sometimes a substrate material is so porous that it actually takes two seal coats to fully seal the surface. This isn't common, but it does work just fine. You'd apply the second seal coat about four hours after finishing the first one, then resume the epoxy process as normal per the included instructions.
Second, measure and mix your epoxy components carefully.
You'll want to measure by volume using graduated mixing containers. We offer some high quality containers on our store, and you can likely acquire them at many home improvement retailers. The ratio for our table top epoxy is 1:1, so the resin and hardener will be blended together in equal amounts.
For deep pour epoxy, the ratio is 2:1, so you'll use more resin than hardener. For instance, four ounces of resin would be mixed with two ounces of hardener.
When you mix epoxy, the method is determined by the quantity being mixed. For anything less than about a gallon, you should use stir sticks to manually stir the epoxy together, being sure to occasionally scrape the sides and bottom to prevent too much residue from building up and to guarantee a good blend.
If you're mixing a batch-size of a full gallon, you can use an electric drill with a mixing drill bit. We strongly recommend the Workforce 1-Gallon Helix Paint Mixer (Model #HM1HD) drill bit, as it has been the most consistent at full blending in our experience.
Before you start mixing, make sure you've read your instructions, as these will explain the exact settings and the duration of your mixing phase.
How do you remove air bubbles?
Formation of some air bubbles during the process is expected, and removal is straightforward. On the other hand, removing air bubbles from cured or mostly-cured epoxy is more difficult and will require a recoating afterward.
Let's go over both methods:
During the process: use a propane torch (or a heat gun).
When you pour a flood coat, it's almost inevitable to get a few bubbles here and there, even with a proper seal coat. This is easily dealt with using a propane torch, or a heat gun if you're uncomfortable with using a torch.
After pouring the flood coat, you'll use the propane torch to remove air bubbles by hovering it a few inches away from the epoxy surfaces while moving back and forth until you've briefly heated the entire surface.
Keep in mind the following tips:
- Don't linger for more than a second over any spot. If you linger, the epoxy will rapidly heat, and you might cause heat damage to the surface which will show itself later when it cures.
- Don't let the flame touch the epoxy. You should be at a reasonable distance, a few inches away. It just needs the heat, not the flame, to remove the bubbles.
- Don't use a hair dryer or anything similar. Most other appliances aren't intended for this and are more about forceful air flow, which for epoxy can mean sending particles and dust into your resin.
After you go over the epoxy resin once with your torch or heat gun, wait ten minutes; then do it again. This is to make sure you remove any air bubbles that hadn't been able to surface originally.
You can lower your perspective to almost parallel to your surface, and it will be much easier to see air bubble blemishes due to how they deflect light at sharp angles.
This method is the optimal way to remove the bubbles, but it must be done during the process, before the epoxy has hardened.
After the epoxy has hardened: Sanding and acetone.
If the bubbles are surface level:
- Sand the surface lightly.
- Wipe the surface with acetone. Wait 30 minutes for it to evaporate.
- Apple a new seal coat to fill in blemishes. Wait four to six hours.
- Apply a new flood coat to the entire surface.
If the bubbles are deep within the epoxy:
- Sand heavily, removing most of the flood coat until you've cleared every air bubble.
- Wipe the surface with acetone. Wait 30 minutes for it to evaporate.
- Apply a seal coat. Wait four to six hours.
- Apply a second seal coat. Wait four to six hours again.
- Apply a new flood coat.
Note: If you attempt to spot fix instead of recoating the entire surface with a flood coat, you'll end up with an uneven surface; it's best to give it a full, smooth coating over its entirety.
You can find digital copies of our epoxy instructions on our support site:
And that's it. We hope this has been useful for you. Read below on how to contact us for additional help.
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