How to Remove Bubbles from Epoxy Resin

Pick your resin by how deep the pour is. A sphere, a paperweight or a thick block needs a deep pour resin. It cures slowly, over 48 to 72 hours, so it stays runny long enough for bubbles to rise out by themselves. A 1:1 coating resin poured that deep heats up and sets in a couple of hours, trapping every bubble inside. Read the bottle for the maximum pour depth.

Check the mix ratio on your resin. Steve's deep pour is 2:1, two parts resin to one part hardener. Mark the fill lines on a graduated cup with a marker before you start. For 300 ml of part A, he adds 150 ml of part B, so the second line sits at 450. Marking first means you pour carefully to a line instead of guessing with a full bottle in your hand.

Mix slowly and keep the paddle under the surface the whole time. Steve uses a handheld electric resin mixer. Put the blade in the resin before you switch it on, and switch it off before you lift it out, or it will splatter and whip in air. Mixing by hand works too. Stir slowly, scrape the sides and bottom, and keep going for the full time on your label.

Pour low and slow. Hold the cup close to the mold and let the resin run in as a thin stream. A fast, chunky pour folds air into the resin and traps bubbles against the mold walls. Steve fills both sphere molds at the same speed right to the top. You will still see some bubbles at this point. That is normal; the next two steps deal with them.

Give the filled mold a few gentle taps on the table, or tap around its sides with your fingers. The vibration shakes bubbles loose from the walls so they float up to the surface. Thin resin lets them rise faster. Deep pour resin stays thin for hours, which is why it gives such a clear result. Watch the top and you will see the bubbles gather there.

Pass a long-neck lighter flame quickly across the resin surface. The heat thins the top layer and pops the bubbles that have risen. Keep it moving and do not hold it in one spot. Steve uses a lighter, never a torch, on silicone molds, because a torch will burn the silicone over time. Make two or three passes, then leave it alone.

Let the resin cure fully before you open the mold. The fast resin was hard in about two hours. The deep pour took the full 48. Stiff molds can grip, so Steve sprays a little soapy water into the gap first. Then flex the silicone and push the sphere out. A more flexible mold lets go without the water.

Hold the finished cast up to a light, or set it on an LED base. Light shining through shows every bubble. The fast 1:1 sphere looked fine at first glance, but on the light it was full of tiny bubbles stuck near the edges. The deep pour sphere was almost clear. If yours is bubbly, the fix for next time is usually a slower resin.