How to get rid of bubbles in resin and fix sticky epoxy that won't cure
TUREFF• •0
Bubbles and sticky surfaces are the two problems almost every resin artist meets. The good news is that both usually have clear causes, and once you know them, most can be prevented before you pour. This guide covers where bubbles come from, how to clear them, and what to do when resin stays tacky.
Where bubbles come from
- Mixing: whipping the resin fast folds air in.
- Cold resin: cold epoxy is thick, so air cannot rise out, and it can look cloudy with tiny bubbles.
- Porous materials: wood, paper, dried flowers and some fabrics release air as resin soaks in.
- Moulds and objects: air hides in corners of moulds and around embedded items.
- Pouring from a height, which traps air as the stream folds over.
Preventing bubbles
- Warm the resin first. If your room is cool, stand the closed bottles in a warm (not boiling) water bath for a few minutes, then dry them completely. Warmer resin is thinner and releases bubbles more easily. Warming does shorten the working time.
- Keep the room warm within the range the manufacturer recommends.
- Mix slowly and deliberately, keeping the stick in contact with the bottom of the cup rather than lifting and whipping.
- Let the mixed resin rest for a few minutes if the product instructions allow, so bubbles rise.
- Seal porous materials first. Coat wood or paper with a thin layer of resin (a seal coat) or a sealer compatible with your resin, and let it set before the main pour. Make sure inclusions like flowers are completely dry.
- Pour low and slowly, and in moulds, brush a thin layer into detailed areas first.
Removing surface bubbles
- Heat gun or small torch: pass it quickly over the surface a short distance away, keeping it moving. The heat thins the resin at the surface and bubbles pop. Do not linger, or you can scorch, ripple or overheat the resin, and never torch silicone moulds closely.
- Fire safety: never use a flame near alcohol inks, isopropyl alcohol, solvents or anything still wet with them, as they are flammable. Use a heat gun instead in those cases.
- Toothpick: pop stubborn individual bubbles.
- Check again after ten to fifteen minutes, as more bubbles often rise.
- Some artists spritz isopropyl alcohol on small mould pieces, but use it sparingly and never near a flame.
Why resin stays sticky
A cured epoxy should be hard and not tacky. If it stays sticky, the cause is usually one of these:
- Wrong ratio: the mix ratio was not followed, or volume and weight were confused. Even a fairly small error can leave resin permanently soft.
- Not mixed enough: unmixed resin and hardener stay liquid. This often shows up as sticky patches or streaks, especially from resin scraped off the sides of the cup at the end.
- Too cold: low temperatures slow the cure dramatically, and some resins never fully harden if kept cold.
- Humidity or moisture: damp air can leave a greasy or waxy film on the surface of some epoxies, called amine blush, over resin that is hard underneath. Water in the mix causes cloudiness.
- Too much colourant: adding more than the recommended amount of pigment, ink or other additive can interfere with curing.
- Old or contaminated resin: past its shelf life, or with the wrong hardener.
How to fix sticky resin
- Wait first if it is just slow: move the piece somewhere warmer and give it more time. Check the full cure time on the data sheet.
- Greasy film over hard resin: wash the surface with warm soapy water, rinse, dry fully, and wipe with isopropyl alcohol. If it is hard underneath, you can then lightly sand and recoat.
- Sticky patches: scrape off the soft resin with gloves on, clean the area, sand lightly and pour a fresh, carefully measured and mixed coat.
- Soft all the way through: an off-ratio or badly mixed batch generally will not cure by itself. Remove it and start again.
Pouring a fresh coat straight over a liquid, sticky layer rarely solves the problem; the soft layer stays soft beneath.
Have you rescued a sticky pour, or found a bubble trick that works? Share it, or ask your question, in the comments.