You mixed the epoxy carefully, waited the full cure time, and the surface is still sticky. A tacky epoxy surface is a common processing fault, not a ruined part. Understanding why it happens tells you whether to recoat, sand, or scrap, and how to keep it from recurring. Why epoxy cures tacky Off-ratio mixing: epoxy cures by a stoichiometric reaction between resin and hardener. Even a small error, especially too much hardener, leaves unreacted material that never hardens. Volumetric and weight ratios are not interchangeable; use the one the data sheet specifies. Under-mixing: resin and hardener that are not blended thoroughly, including the material clinging to the sides and bottom of the cup, leave streaks and pockets of uncured epoxy. Low temperature: most epoxies need a substrate and ambient temperature above roughly 18 to 21°C to cure fully. Below that, the reaction slows or stalls, leaving a soft or tacky film. High humidity and amine blush: some amine-cured epoxies react with atmospheric moisture and carbon dioxide to form a greasy carbamate layer on the surface, which feels tacky or waxy even when the bulk is hard. Insufficient cure time: thin films and cool conditions can extend cure well beyond the data sheet's nominal figure. First, identify the cause Press a gloved finger into the surface. If it dents and stays soft throughout, the mix was likely off-ratio or under-mixed and the whole layer is compromised. If only a thin surface film is greasy over a hard mass beneath, you are probably looking at amine blush, which is repairable without removing material. Fixing amine blush Blush is water-soluble. Wash the surface with warm water and a non-abrasive pad, dry it fully, then wipe with isopropyl alcohol. The tackiness should disappear, exposing hard epoxy underneath. Once clean and dry, the surface can be top-coated or finished normally. Fixing an under-cured layer If the epoxy is soft through its thickness, it will not harden further on its own. Two options: Recoat: scrape or wipe off as much uncured material as possible with isopropyl alcohol and a lint-free cloth, then apply a fresh, correctly measured and mixed coat over the sound surface and cure it in a warm space Remove and restart: for structural parts or thick pours, remove the bad layer entirely rather than trapping soft epoxy under a new coat Fixing a thin tacky film over sound epoxy Sand lightly with 120 to 220 grit until the stickiness is gone, staying well within the cured layer. Wipe off the dust with a damp cloth, let it dry, and apply a thin clear top-coat if a finished surface is needed. Email Us with your epoxy system and conditions if a tacky surface keeps recurring. Preventing it next time Measure with calibrated mixing cups or a graduated dispenser, not by eye, and follow the specified ratio by weight or by volume as stated Mix for the full recommended time and scrape the container sides and bottom, then transfer to a second cup and mix…