How to fix sticky spots of uncured resin

Sticky or tacky patches after your resin should have cured are almost always caused by one of a handful of measuring or mixing mistakes — not a bad batch. This guide covers what causes it, how to fix an affected piece, and how to avoid it next time.

Common causes

• Ratio measured by weight instead of volume. Equal weights of resin and hardener are not equal volumes — the two components have different densities. Craft Resin ratios (1:1 or 2:1 depending on product) are all specified by volume.
• Ratio poured off slightly. Even a small error in the pour throws off the chemical reaction, and the resin never fully hardens in the affected area.
• Under-mixing. Resin and hardener need to be combined thoroughly enough that no streaks or unmixed patches remain.
• Unmixed resin from the container walls. Scraping the sides and bottom of the mixing cup can pull in resin or hardener that never got properly combined into the main mix, creating small sticky pockets once poured.
• Room too cold. Curing chemistry slows down significantly below the product's ideal working temperature.
• Humidity too high. Moisture in the air can interfere with cure, and some products are more sensitive to this than others.
• Not enough time has passed yet. This is the most common false alarm — checking a piece before its hard cure time is up and mistaking "still curing" for "did something wrong."

Hard cure times by product

Don't judge a piece as faulty until its hard cure window has actually passed.

"Hard cure" means the surface is dry to the touch — it isn't the point at which the resin has finished reacting. Full mechanical strength and scratch resistance on epoxy products isn't reached until around 21 days, so don't judge scratch resistance or do heavy handling before then. If a piece is still tacky well after its hard cure window, that's a real problem worth fixing, not just impatience.

How to fix it

1. Confirm the cure window has actually passed. Check the hard cure time for your specific product above before doing anything — resin that's simply not finished yet doesn't need fixing, just more time.
2. Scrape away the soft resin. Use a plastic scraper or craft knife to remove all of the tacky material down to a clean, cured surface. Don't leave any soft residue behind.
3. Wipe and lightly sand the area. Clean the exposed spot with isopropyl alcohol, then sand lightly so the new layer has something to grip and the repair blends in rather than sitting as a visible ridge.
4. Re-mix a fresh batch, measured by volume. Use the correct ratio for your product, mix thoroughly, then transfer the mix into a second clean cup and mix again — this two-cup method catches any unmixed resin left on the sides of the first container.
5. Pour a thin layer over the repaired area and leave it undisturbed. Feather the edges into the surrounding cured resin, then let it go through its full hard cure time again before touching or testing it.

Preventing it next time

• Measure both parts by volume, using markings on a proper mixing cup — not a kitchen scale, unless a product's instructions specifically call for weight.
• Mix thoroughly and scrape as you go, then scrape and re-mix in a second cup rather than pouring straight from the first.
• Keep the room within the ideal temperature range for your product. Below 15°C, warm the resin component to around 30°C before mixing.
• Check humidity, particularly with Table Top, which is the most sensitive product in the range to moisture in the air.
• Wait out the full hard cure time before assessing the surface — checking too early is the single most common reason people think a piece has failed.

Related articles

• Mixing Ratio — How to Measure Resin and Hardener Correctly
• Sticky or Soft Result — Troubleshooting Incomplete Cure