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Understanding the Resin Encapsulation Process Part 2

Preventing Bubbles When Encapsulating Objects in Resin

Encapsulation projects with epoxy resin have gained immense popularity for their ability to protect, enhance, and immortalize various items. While resin encapsulation seems straightforward, several variables can lead to undesirable results. Incorrect application techniques, use of highly detailed or porous objects, improperly preparing organic materials, inattentive or hurried pouring, or overheating the casting can all lead to unsuitable outcomes.

Bubbles in a casting are a common issue. There are a number of variables that can contribute to bubbles being formed or trapped in an encapsulation casting. FlowCast, the best resin from EcoPoxy for encapsulations, is a slow-curing, low-viscosity resin. This allows bubbles ample time and opportunity to escape a normal casting. However, when it comes to encapsulation, circumstances can often cause complications. A deeper casting depth can speed up the cure time, giving the bubbles less time to escape. The use of cooling on an encapsulation, like putting the casting in a fridge, can increase the viscosity of the resin and make it harder for the bubbles to escape. Objects with curved or detailed surfaces can trap bubbles against them.

Below we will be exploring these common causes of bubbles in your encapsulations and how to prevent them.

Bubbles Introduced When Mixing Resin: 

One of the most often overlooked methods of introducing bubbles into resin is during the mixing process. FlowCast is mixed at a 2:1 ratio of resin to hardener, and should be mixed for 4-5 minutes. During this time, aggressive mixing or whipping the resin (an excessive use of speed and introduction of bubbles) can occur. When this occurs, the resin will look cloudy or foamy despite being fully mixed. This process introduces hundreds of thousands of bubbles into the resin, and can make it extremely difficult to get a bubble-free casting.

To avoid this:

  • Start mixing slowly
  • Mix from the bottom up
  • Do not move the mixer head above the resin surface
  • Mix at a moderate speed
  • Scrape edges and bottom of the mixing container with some kind of stir stick

Bubbles Introduced When Pouring Resin:

One often overlooked method of introducing bubbles into resin is during pouring. Pouring resin too quickly can introduce bubbles by churning the resin and entrapping air, much like when the resin is mixed too quickly. Also, when pouring around an object being encapsulated, pouring directly onto the object can trap bubbles in pockets and fine details.

To avoid this:

  • Start pouring slowly
  • Pour from high above the casting
  • Pour onto a stir stick to lessen the impact of the resin on the surface of the casting
  • Pour directly into voids as much as possible
  • A stir stick can be used to direct flow into voids as well
  • Pour the resin onto the stir stick to guide it into specific casting areas
  • Pour away from the encapsulated object and allow the resin to flow and fill in gaps

Getting Bubbles Out of Your Resin

Once the bubbles have been introduced to the resin there are ways to get them out before and after you pour. If there are only a few bubbles you can use some kind of heat before pouring to thin the resin further and allow the bubbles to escape faster and easier. This can be done by filling a larger mixing cup with hot water and placing the resin filled cup in the water. (Be sure not to let the water and resin mix as this will cause problems in your curing process.) If there are lots of bubbles or you are worried about microbubbles you can de-gas your resin in a vacuum chamber. This process uses the vacuum to pull the bubbles out of the resin. If you are using this process be careful the resin does not overflow in the vacuum chamber as the vacuum will pull the bubbles upward.

If the resin is already in the casting, there are ways to decrease the bubbles trapped there. Torching the surface of the resin, if it wont damage your encapsulation, is always an option.

Or if the bubbles are stubborn and caught by your object, you can use a long metal pick or a toothpick to:

 Gently guide bubbles out of where they have been caught

  • Gently depress or move aside flowers to free bubbles
    • Be very careful: broken petals will allow resin into the membranes and break will become very obvious
  • Gently nudge bubbles trapped in the details until they release from the surface of the object

You can also coat your objects before encapsulating to help prevent bubbles from becoming caught against the object’s surfaces, or from being released into the resin by porous objects.


Bubbles are a very common issue when casting with any kind of resin, this is made more prevalent when casting encapsulations. Following manufacturer instructions on how to use the product is the best way to prevent them in your castings. If you do want to experiment, always do small-scale trials representative of your project before attempting a full-scale encapsulation.