Hand up if you hate bubbles in resin! (I have both of mine up in case you are wondering.) Nothing can ruin the look of resin quicker than finding a bubble in your finished project. Here are my 10 tips for avoiding and getting rid of resin bubbles.
1. Choose the right resin for your project.
If you are casting into molds, choose a resin that is designed for casting. They mix in a thinner viscosity, so it is less likely you will introduce bubbles into the resin. Even if you do, they also tend to release easier since the resin and hardener mixture is thinner. Thicker resins, meant for doming projects, generally hold bubbles, especially with thick castings. Doming resins are better suited for thinner pours.
Not sure which resins are doming versus casting? Find out more here:
2. Cast resin in a warm room.
I realize that certain times of the year it can be difficult and expensive to run a heater all the time, but resin likes an ambient room temperature of 70 to 75 degrees Fahrenheit for curing. If it is a little impractical to heat your whole house or apartment, try heating a smaller space such as a bathroom or closet. Use something like a space heater to generate enough warmth so that the area stays warm during the entire curing time. You can also try making a resin ‘hot box’ for your projects. This works great for smaller undertakings like casting resin into molds and bezels. Here are some ways to make a resin hot box:
3. Warm your resin before casting.
Warm water in your microwave so it’s hot, but not boiling. Place your resin and hardener bottles in a plastic bag, then let the bag sit inside the hot water bath for five to ten minutes. Be aware, you do not want to get water in your resin. This could keep it from curing! Note: By keeping the resin in the plastic bag, you will not wash off your label instructions and safety information. Warming your resin before use is helpful even if it is summertime as bottles generally are still cool to the touch. Be careful that you don’t overdo it. Yes, there is too much a good thing. If your resin is too warm when mix it, you will shorten your pot time.
4. Be careful when mixing.
You are not scrambling an egg! Mix deliberately, but carefully, while going along the sides and bottom of the cup. Sometimes when mixing large volumes of resin, it’s hard not to introduce bubbles that may not rise to the resin surface before casting or pouring. Know that you will need to have a way to get rid of these bubbles once you have cast the resin.
5. Make sure the surface you are pouring your resin in or on is also warm.
Temperature differences will produce surface tension which means bubbles can be trapped when the resin is poured. Gently warming your casting top/mold/bezel with a heat gun is an easy way to warm up the area. If you are working with molds that are oven-safe, you can also gently warm them (generally to 150F) before use.
6. Decrease the surface tension of a mold by dusting a powder on the surface.
A small amount of baby powder can work to reduce bubbles in resin. If you are using colored resin, you can even choose a powder that matches the color of the resin you are using. Use a delicate paintbrush to dust in the powder, then tap out any extra before pouring.
7. Roll the resin around your mold/bezel before completely filling the vessel.
This also helps to break the surface tension. If you do get any bubbles, they will be easier to pop now because there is less vertical space for them to move. You have them trapped!
8. For intricate molds, pick them up and try to ‘demold’ the resin several times during pouring.
This will let any trapped bubbles in creases to escape. You can see what I mean in this article: How to make a blue sparkle resin ring
9. Dip inclusions in resin before putting them into your mold/bezel. This also breaks the surface tension.
Once you have dipped them into the resin, put them into your mold or bezel on an angle, then move into place. By putting an inclusion flat onto a resin surface, you will likely trap bubbles underneath. This article shows how to put things in on an angle: How to make resin pendants
10. Once you have cast all your resin, go over it a final time with a heat source to pop bubbles.
I like to use a heat gun, but I know others will also use a butane torch or barbecue lighter. Please use caution when using a flame! You should have a fire extinguisher nearby. Also, know that excess heat may warp plastic molds.
Bonus tip: If all else fails and find you are still struggling with removing bubbles from your castings —
11. Use a pressure pot.
With some resins (like clear polyurethanes) and/or large castings, the only way you can get rid of bubbles is to use a pressure pot. This is a system where your mold and casting are placed into a pot and pressure is created within the pot. This pressure makes the bubbles smaller than the eye can see. The pressure needs to remain on the casting the entire time during which the resin will cure bubble-free.
What else do you like to do to get rid of resin bubbles?
Want to learn other resin basics to help you make something that will have people saying, “Whoa, you made that?!” Then you will want to get a copy of the PDF ebook, Resin Fundamentals. It contains everything you need to know to go from confused to confident with resin. Buy now and read it today!
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