Resin Troubleshooting Guide
How to Use This Guide
Find your problem below, read the likely causes, and follow the fix. Most resin issues come down to measuring, mixing, temperature, or contamination. This guide covers the most common problems and how to prevent them from happening again.
Problem: Resin Is Cloudy or Milky
Cause: Moisture contamination, cold temperatures, or improper mixing. Humidity above 50 percent introduces moisture into the resin during mixing and curing. Cold resin below 70 degrees F becomes thick and difficult to mix thoroughly, trapping air and creating a hazy appearance. Undermixing leaves unmixed resin and hardener that cure improperly and appear cloudy.
Fix: Work in a warm, dry environment above 75 degrees F with humidity below 50 percent. Warm your resin bottles in warm water for 5 to 10 minutes before mixing to reduce viscosity. Mix slowly and thoroughly for the full recommended time, scraping the sides and bottom of the cup. Ensure all tools and molds are completely dry before use.
Prevention: Control your workspace temperature and humidity. A space heater and dehumidifier are worthwhile investments for a resin studio.
Problem: Resin Did Not Cure or Is Still Sticky
Cause: Incorrect ratio, undermixing, or cold temperatures. This is the most common resin problem and almost always comes down to measuring or mixing error. Even a small deviation from the correct ratio can prevent proper curing. Unmixed resin or hardener that clings to the sides of the cup will remain liquid or tacky after the rest of the pour cures.
Fix: If the resin is still soft and flexible after 48 hours, it may still cure with additional time and warmth. Move the piece to a warmer location and give it another 24 to 48 hours. If the surface is tacky but the piece is otherwise cured, you may be able to apply a fresh thin layer of properly mixed resin over the top to seal it. If the piece is completely uncured and liquid, it cannot be saved and must be discarded.
Prevention: Measure precisely using graduated cups or a digital scale. Mix for the full recommended time. Scrape the sides and bottom of the cup throughout mixing. Never rush the mixing step.
Problem: Bubbles in the Finished Piece
Cause: Air introduced during mixing, cold resin, or pouring too fast. Mixing too aggressively whips air into the resin. Cold resin is thicker and traps bubbles more easily. Pouring from too high above the mold introduces air as the resin falls.
Fix: Surface bubbles can be popped with a butane torch or heat gun immediately after pouring. Deep bubbles that formed during mixing cannot be removed after the pour. If bubbles are a recurring problem, slow down your mixing technique and warm your resin before mixing.
Prevention: Mix slowly and deliberately. Warm resin bottles before mixing. Pour close to the mold surface. Let mixed resin sit for 1 to 2 minutes before pouring to allow surface bubbles to rise and pop on their own. Use a torch in slow passes over the surface immediately after pouring.
Problem: Fish Eyes or Craters on the Surface
Cause: Silicone contamination, dust, oils, or debris on the mold surface. Even a tiny amount of silicone from a spray, lotion, or nearby product can cause resin to bead up and refuse to wet the surface, creating craters or fish eyes.
Fix: Fish eyes that form during a pour cannot be fixed mid-pour. After curing, sand the surface smooth and apply a fresh layer of resin. Identify and eliminate the contamination source before the next pour.
Prevention: Clean molds thoroughly with isopropyl alcohol before each pour. Keep silicone-based products out of your studio. Avoid touching the mold surface with bare hands since skin oils can also cause adhesion issues.
Problem: Resin Yellowed After Curing
Cause: UV exposure, low-quality resin without UV stabilizers, or excessive heat during curing. All epoxy resin will yellow eventually with prolonged UV exposure, but high-quality UV-stabilized resin resists this significantly longer. Excessive heat during curing, such as from direct sunlight or a heat lamp too close to the piece, can also cause yellowing.
Fix: Yellowing in a cured piece cannot be reversed. The piece can be sanded and recoated with a UV-resistant topcoat to slow further yellowing, but the existing color change is permanent.
Prevention: Use UV-stabilized epoxy resin. Keep curing pieces out of direct sunlight. Store finished pieces away from prolonged UV exposure. Apply a UV-resistant topcoat as a final finishing step.
Problem: Resin Has a Wavy or Uneven Surface
Cause: The mold or work surface was not level during curing, or the resin was disturbed before it set. Resin self-levels but only if the surface it is sitting on is level. Any tilt will cause the resin to flow to one side and cure unevenly.
Fix: Sand the high spots down and apply a fresh flood coat of resin to level the surface. Ensure your work surface is perfectly level before the next pour.
Prevention: Use a spirit level to verify your work surface before every pour. Do not move or disturb the mold for at least 24 hours after pouring.
Problem: Resin Pulled Away From the Mold Edges
Cause: Surface tension, contamination at the mold edges, or resin that began to cure before it could fully wet the mold surface. This is more common with low-quality molds or molds that have been used many times and have micro-scratches or residue buildup.
Fix: After curing, sand the edges smooth and apply a thin layer of fresh resin to fill any gaps. Clean the mold thoroughly before the next pour.
Prevention: Ensure molds are clean and dry. Pour slowly and allow the resin to flow naturally to the edges rather than forcing it. Tilt the mold gently if needed to encourage the resin to reach all corners.
Problem: Resin Is Too Thick to Pour
Cause: Cold resin, resin that has begun to cure, or resin that has exceeded its pot life. Epoxy resin thickens as it cures. Once it reaches a gel state it cannot be poured and should not be forced into a mold.
Fix: If the resin is cold, warm the bottles in warm water before mixing. If the resin has already been mixed and is thickening, work faster. Do not add heat to try to thin mixed resin that is gelling as this will accelerate the cure and generate excessive heat.
Prevention: Warm resin before mixing in cold environments. Work within the pot life specified by your resin brand. Mix only as much resin as you can pour within the working time.
Problem: Resin Generated Excessive Heat During Curing
Cause: Pouring too thick, mixing too large a volume, or working in a very warm environment. Epoxy resin generates heat as it cures through an exothermic reaction. In thick pours or large volumes, this heat can build up to dangerous levels, causing the resin to crack, smoke, or in extreme cases catch fire.
Fix: If you notice excessive heat or smoke during curing, move the piece to a safe outdoor location away from flammable materials and allow it to cure. Do not pour water on it. The piece will likely be damaged but the priority is safety.
Prevention: Never pour epoxy resin deeper than the manufacturer's recommended maximum depth per layer. For deep pours, use a resin specifically formulated for thick pours and pour in multiple thin layers. Work in a cool environment and avoid pouring large volumes in a single batch.
Still Having Issues?
If your problem is not covered here, visit the Ask the Creator Q&A or contact me directly. I am happy to help troubleshoot.