Epoxy is an amazing product. It is used for covering tables, floors, counters, high-traffic areas, outdoor furniture, and casting different objects. As the popularity surrounding epoxy grows, so do the uses for it. One of the changes in how epoxy is used is for deep casts and pours. When these are done, many things become more difficult and intricate in the pouring process.
It is difficult to get completely bubble-free epoxy, however, you can get very close (if not all the way there). If nothing else, you can remove the bubbles after stirring the epoxy and after pouring – creating a bubbleless end product.
While it is difficult to achieve perfection with epoxy resin pouring, there are many precautions one can take that can improve this process. Below, I have outlined 13 tips and tricks that can help you keep your epoxy bubble-free while pouring. Paying attention to these suggestions, you should be well on your way to enjoying the end results of a smooth epoxy finish. Let’s take a closer look.
13 Tips to Prevent and Remove Bubbles from Epoxy
1. Use a Low Viscosity Epoxy
Several epoxy resins tout an ability to release bubbles during the cast. This is becoming more of a standard in the industry, as pours are being done deeper and deeper. When you consider how many different projects that you might want to get done (or even just the excitement of completing one project at a time), you tend to want to pour the epoxy as deep a pour as possible to save some time.
Fortunately, using the right products and the right setup can make this possible. Thankfully this is an ever-improving industry, so by the time you read this post, there are probably multiple, great, affordable types of epoxy on the market.
Still, the main reason an epoxy resin is quick to release bubbles is when the viscosity is low (which means it is a lot thinner of an epoxy). Consider if you were pouring brownie batter from a bowl to a pan, preparing to make a fresh batch. If your batter is thick and lumpy, it will consequently be this way in the pan. However, when it is thinner, it spreads out more evenly as you quickly pour it out.
Similarly, when attempting to remove bubbles from epoxy (especially when trying to achieve a deep pour), you want to use a thinner epoxy i.e. one that has a low viscosity. Fortunately, this is becoming more and more common. If you want my opinion on these types of epoxy, I have added it at the bottom or you can check out my recommended epoxies page.
Regardless of which you choose, without a doubt, the first step to preventing bubbles in your epoxy is to find an epoxy that has a low viscosity. Any manufacturer/retailer will be able to inform you of this, and it should not be difficult to find this on the label or marketing product description.
2. Warm the Epoxy Resin First
While it is true that too much heat on resin can be a bad thing, cold resin is thicker and will hold more, larger bubbles. Again, going back to the brownie batter comparison example, if you were to mix up your brownie batter and then place it (in its bowl) in the fridge, pulling it out a little while later and hoping it will fill in all spots of the brownie pan you will bake in seems ridiculous.
Using an easy scientific explanation, the particles of a substance (like epoxy) will come together (contract) when they become heated. Contrarily, the absence of heat will cause the particles to expand.
Consequently, when epoxy loses heat (i.e. becomes cold), it expands unevenly and can cause the bubbles (that you are attempting to get rid of) to form. Using the application of heat (even at a mild or moderate level) can help the particles to contract again and create a smooth substance.
One way to warm the epoxy resin first is before mixing your hardener and base resin. Before you start to mix these two, it can be helpful to warm up the bottles that they are in. Then, the substances will increase in temperature and decrease in the bubbles that they would otherwise form.
To do this, place the bottles (of your hardener and base resin) in plastic bags, and let them sit in hot (not boiling) water for a few minutes. This will prevent water from getting into them, but allow them to warm up and lower in their viscosity. Consequently, you should enjoy pouring epoxy without bubbles.
3. Use a Non-Porous Material to Stir
Using a non-porous material to stir your epoxy will be a new idea for many people working with epoxy. Non-porous does not have to be a particular material. Rather, you are looking for a piece of material to stir your epoxy with that does not have crevices that can disrupt the continuity of the epoxy’s surface.
In my opinion, plastic is a great way to go when you want to stir your epoxy with a non-porous material. Using plastic cutlery is an affordable (aka cheap) and incredibly accessible way to mix smaller epoxy pours.
Once you get into larger amounts of epoxy, you can get drill attachments like this one that are steel and plastic (non-porous) to keep the bubbles in your epoxy to a minimum. These work well to prevent the bubbles from forming as you stir the epoxy, acting as a preventative measure rather than a reactive one.
One common mistake that causes bubbles for a lot of new epoxy workers is using wooden sticks to stir. This is common practice for paint, but these materials are significantly different. Wood is porous and this causes bubbles to form all over and fill the surface of the epoxy. While you would not notice this in paint (because it is thin and has a relatively standard temperature), this is highly noticeable when using epoxy.
4. Mix Under the Surface
If you are using the aforementioned drill stirrer, you want to be sure to keep the drill completely submerged while it is moving. If it breaks the surface while spinning it can cause air to penetrate the surface and get lodged into the epoxy.
As you mix under the surface, you will want to slowly and steadily turn off the drill and raise it gently out of the epoxy once you have completed stirring it. Raising the mixer too quickly can cause it to disrupt the evenness you have worked so hard to attain, so be sure to take your time with this last little bit of the mixing process. (Again, back to the brownie example, you can think about what happens when you raise a mixer out of brownie batter too quickly- sending batter flying everywhere and an uneven mix.)
If you are mixing by hand, there is no way to prevent this. Even if you were wearing protective gear, sticking your entire hand and mixer under the surface would not be a good idea. Since your hand is an uneven surface and is not entirely non-porous, even if you were to place it under the surface, this would not help to prevent bubbles in your epoxy. Much less, it would be a huge mess.
5. Don’t Scrape Sides While Mixing
When mixing by hand, you want to be cautious about scraping the sides of your container while mixing. This is a common desire considering that mixing near the sides causes a wider portion of the epoxy to get mixed around more quickly. However, stirring with your stirring material on the outermost portion of the container (near the edges) can cause you to scrape the sides and allow a large flow of air to infiltrate the epoxy.
Instead of spending time with your mixer on the sides of your container, mix for longer with your stirring material in the center- working all the way out to the sides much less frequently. Mixing on the sides causes large air gaps throughout the epoxy which is the primary cause of bubbles being formed.
So, while it might seem like it is taking forever to get the “whirlpool” vortex going in your epoxy by keeping your stirring rod in the middle of the container, this will prove much more effective for a smooth, bubbleless product. Consequently, you can avoid creating bubbles in the epoxy before you even begin to pour it.
6. Wait After Mixing Before Pouring
While most of us are eager to get started once we have finished mixing our epoxy, it is important to wait after mixing before pouring. Specifically, once you have finished with mixing, you want to give it a few minutes before pouring regardless of if you are pouring a deep or shallow epoxy pour.
The reason behind this is that allowing the epoxy to sit will give the air time to rise to the surface, resulting in fewer bubbles spread throughout the pour. Alternatively, if you were to pour the epoxy immediately after mixing, any bubbles that had been stirred up in the interior of your mixing container would not have had a chance to rise and could become stuck inside your pour.
Therefore, if you want to take preventative action and avoid seeing bubbles form in your epoxy pour (deep or shallow), it is best to wait a few minutes after mixing. This does not have to be an exceedingly long process, but taking even just a few minutes can help to reduce this enough that it is worth it.
7. Misting With Acetone
Misting your epoxy with acetone is a less beloved solution for reducing bubbles in your pour. However, the idea is that lightly misting the top of the mixed epoxy with acetone will briefly lower the viscosity and cause more bubbles to come out. While some critics will say this could compromise the epoxy, I disagree because acetone is probably the fastest evaporating solvent on the market.
However, keep in mind that when I say misting, I mean applying a very light mist- not soaking your epoxy. You can do this by placing a small amount of acetone in a fine-spray bottle and then lightly spraying the epoxy from about 5-12 inches from the surface. Avoid creating large pools, but know that this is unlikely if you are truly attempting a mist.
8. Use a Vacuum Container or Pressure Pot
Post mixing and pre-pouring, it is possible to get all the bubbles out of your epoxy. The way to do this is to use a vacuum container that removes all of the air with your epoxy inside of it. This could also work if you are able to use/buy/build a vacuum container large enough to fit your pour.
Of course, for small pours you are able to purchase a fairly cheap vacuum chamber and pump. These can be safe, effective, and can drastically reduce the bubbles that you would otherwise find in your epoxy. If you are not doing a large table, counter, or floor, it is realistic that you could do a few batches of epoxy in this type of chamber and pump to remove all bubbles. If you are doing one of the larger options though, then this might not work well, and you should use another tip from this list.
9. Warm the Surface You are Pouring Onto
When you pour epoxy, you want the epoxy and surface material to be as similar in temperature as possible. The heat differential could cause bubbles to form between the two during the pour.
There are multiple ways of ensuring that the two (epoxy and surface material) are similar in temperature.
If it is a small mold, this can be as simple as just running a hairdryer over it for a few minutes prior to pouring. Unfortunately, this can be more difficult if you are pouring onto a large surface. In this case, you could place space heaters around the surface that you are working on, which would be the quickest way.
If you have a highly temperature-controlled room, you could raise the temperature for a day, and then, as you pour, lower the temperature in the room to the recommended range. Obviously getting creative is the only way for the average person to control this variable.
10. Make Sure the Surface is Dry
Keeping the mold dry may seem simple, but this is something you definitely do not want to mess up. Any moisture on the surface that you are pouring onto can cause bubbles to form when it is contrasted with resin. Here, whether the surface has visible droplets or is moist, you will not have a satisfactory pour that is without bubbles.
To ensure that the surface is dry, you can begin by running fans over the mold or pressing a paper towel down inside before pouring. As you move about each section, you should find that the paper towel comes back dry. If this is not the case, then you know to address any moisture. This seems simple, but it can make all the difference.
11. Dust the Mold with Talc
Dusting with talc seems to be accepted more in the older forums of working with epoxy – before companies began putting out epoxy with super low viscosity. While it is not very common anymore, I assume it would work the same. I must admit, I prefer to use epoxy with low viscosity, but if you do not have that in stock and are attempting to go ahead with your project, then this option will work.
Brushing the talc very lightly on the surface you are pouring into can pull the epoxy into the crevices that would commonly leave air gaps. If you are going to use this method, be aware that you will likely need to sand down or even plane that side of the project in order to move the talc. Still, with how effective it can be, it will be worth your efforts in the end.
12. Seal Surface Before Pouring
Sealing the surface before pouring your epoxy is a suggestion that will vary based on the application of the epoxy. In general, I focus on woodworking with epoxy. When pouring epoxy alongside wood (or any porous material) it is good to seal the material first.
This can be done by taking a small amount of epoxy and brushing it only the areas that you are pouring the epoxy into. This can help prevent many bubbles, but it also saves epoxy from seeping into the material and costing you extra epoxy.
However, if you are working on other types of materials or have an interesting cast, you might not be able to seal the surface. In this case, it is recommended to use another method that can help you to achieve fewer (or no) bubbles in your epoxy pour.
13. Use a Heat Gun or Blow Torch Post-Pour
Once your epoxy is poured and in its mold, the final bubbles (hopefully not too many) will be rising to the surface. While this is happening, you can take a heat gun or blow torch and run it quickly across the surface of the epoxy. Due to the application of the heat, the expanded air particles will cause the bubbles to immediately pop, which is also a satisfying feeling.
If you are using a heat gun or blow torch post-pour, you should probably plan to do this at least a couple of times, 2-5 minutes after you pour and then 10-15 minutes after you pour. This will help get any straggler bubbles that are left, and you can always do it once more to be safe. Of course, be sure that you use proper safety precautions and avoid using these near flammable chemicals.
Removing Bubbles After Your Epoxy Has Cured
In case you were unaware, you are able to remove bubbles after the epoxy has already cured. If the bubbles are deep, the work required to do so would be more than re-pouring. If the bubbles are near or on the surface of the epoxy, you can sand down to where there are no bubbles and then re-pour a coat where you sanded to make it look brand new.
Of course, saying and doing are two different tasks. If you plan to sand down epoxy to fix the bubbles, you will want to make sure to take multiple things into account. Here are the steps that you can follow to remove bubbles after your epoxy has cured.
- Figure out how deep you need to go. If you are going to go deep into your epoxy pour (as in the bubbles are evidently several inches or even centimeters down into your pour), you may want to consider re-doing the project, it is a lengthy, difficult task to dig and re-pour deep into hardened epoxy.
However, if you see that you will only need to sand down a little bit to be able to free the trapped bubbles before repouring, then this can be worth it. While it can be incredibly frustrating, it is better to save yourself the effort and wasted epoxy twice by deciding how deep you need to go (and if it is worth it) to remove the bubbles this way.
- Sand down the entire surface. If you are using a mold and do not need to rely on the epoxy to self-level (like when coating without a mold), you can sand at different levels. Sand past the bubbles to make sure that they are out. You will want to keep the sanding under 320 grit so that the second coat will be able to make a strong bond to the sanded coat.
Personally, using a random orbital sander is preferred for this process (especially if the project is larger than a serving tray). You could choose to sand by hand, especially if the project is smaller, but this could be incredibly taxing on your time and energy. Also, I will note that some people like to use a wet sander, but there are many pros and cons to this.
- Clean off the surface (and dry it). Having a clean and dry surface is an important step. If you do not properly clean the surface, you could end up with more bubbles AND dust in your new epoxy pour. Not only would this mean you have visible bubbles (that you were attempting to eliminate) caused by the water droplets, but you would see any chips of epoxy or other particles left behind.
As you clean off the surface of your freshly sanded epoxy project, wipe it thoroughly with a damp paper towel or microfiber rag. Make sure none of the particles from either are left on the table. Allow it to dry fully. If you do not have time to wait, dry it off with a hairdryer.
- Re-pour your epoxy onto the new surface. Now you are ready to begin repouring your epoxy onto the new (freshly sanded) surface. Take extra care to follow the above tips on preventing bubbles. You definitely do not want to have to re-pour (again), so following as much advice as possible will help prevent any bubbles and give you a crystal-clear pour.