There are some factors we need to consider why bubbles came up.
Was I mixing too fast and forcefully? Do not mix epoxy too quickly or rigorously. Vigorous mixing will create additional air bubbles into the mixture before pouring
Did I seal my surface? Some materials are very porous. Be sure not do a thin coat of epoxy first before adding your flood coat to seal the surface. Remember to wait at least four hours after your skim coat to apply your flood coat.
How do I remove bubbles? After pouring your epoxy, immediately be sure to use a plumber torch or heat gun to eliminate most of the bubbles on the surface. Using your heat device in an evenly and continuously moving motion to help remove most of the bubbles on the surface. This step is crucial because it not only levels the epoxy and releases small air bubbles. It will give it a glass-like look.