Although bubbles in resin are sometimes intentionally created as a decorative element, they are more often considered undesirable. How can you ensure that your final product is bubble-free?
The most common recommendation you will receive is to get a vacuum chamber, which removes all the bubbles from the mixed resin due to the vacuum. However, if you don’t have your own workshop and a few extra thousand, a vacuum chamber is probably not an option for you.
So how can you help ensure that your final product is as bubble-free as possible?
First and foremost, remember that bubbles are introduced into the resin when mixing components A and B. Resin needs to be mixed slowly and smoothly, trying to incorporate as few bubbles as possible. The thicker the resin and the faster it cures, the more bubbles it retains. Resins that cure over several days and are very liquid tend to release bubbles more effectively during the early stages of curing up to the gel phase. Therefore, there is still a good chance that bubbles will disappear by themselves in the mold
Tricks for removing bubbles that we use ourselves
1) Are you pouring resin onto a porous substrate?
Be careful – tiny air bubbles may be released from it (and almost certainly will be). Always thoroughly penetrate a porous substrate with either a special penetrant or a thin layer of resin. Depending on the porosity of the substrate, you may need to apply more than one layer. The advantage of penetration is that it soaks into the surface of the material and partially strengthens it from within, better binding it with the subsequently poured resin.
2) After mixing, let the cup with mixed resin sit for a while.
In the cup, the resin is usually in a higher column than intended, which accelerates its curing. Be careful to ensure that the resin does not overheat and cause an exothermic reaction. Monitor the cup regularly. Is it starting to get warm? Quickly pour the resin into the molds. Never let the resin in the cup get hot. Until the resin starts to heat up, it should have released most of the bubbles to the surface, where you can remove them by quickly passing a lighter over the surface or spraying with alcohol spray.
3) Before pouring, you can place the container with component A in warm water for about 15-20 minutes.
The heat will make it more fluid and hold fewer bubbles during mixing. WARNING – this method significantly shortens the working time of the resin; it must be poured immediately after mixing and not left in the cup. If you are a beginner and not yet fully comfortable working with resin, it is better to rely on careful mixing.
4) Another option is to heat the already mixed resin in a warm bath, stir it slowly, let it sit a bit, and release bubbles to the surface.
However, we recommend this only for experienced casters because you will be on a very thin line with the exothermic reaction (rapid heating and curing of the resin, see the link to the article above).
What trick do we use to monitor the temperature if we don’t have a contactless thermometer? When using this method, we submerge about ¾ of the cup in the warm water bath and keep ¼ above the surface. Not only does this help prevent water from getting inside and ruining the resin, but it also allows us to place a finger on the remaining ¼ and check by touch whether the resin is overheating.
5) You can spray 1-2 spritzes of alcohol into the resin and mix it (1-2 spritzes per 100 grams of mixed material).
Alcohol helps remove bubbles, as do alcohol-based pigments. We do not recommend overdoing it with alcohol in the resin. Adding too much can lead to poor curing and a rubbery product. 
6) We know we mentioned this at the beginning of the article, but it is worth repeating: careful mixing.
Resin does not have bubbles; it is our hands that introduce them. Therefore, let’s try to incorporate as few bubbles as possible and avoid dealing with them later.
VIDEO: Removing bubbles from resin
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