Sticky or Tacky Resin Prints After Curing

Likely causes, most common first

1. Wash solvent saturated with resinMost common
   Formlabs notes that, for one of its resins, surfaces may become tacky if washed in IPA with more than 5 percent resin concentration Maker spec, with thresholds varying by resin. Prusa says that in its experience IPA loses its washing ability after about two months of frequent use Rule of thumb.
2. Wash too short for the shapeVery common
   Formlabs says hollow, concave, large or long parts and internal channels need longer washing, as does a solvent bath with a high resin concentration. Some of its resins call for a second wash in clean solvent.
3. Solvent still on the part when it was curedCommon
   Formlabs says to let prints dry fully before post-curing (its wash page adds compressed air for internal spaces on some resins). Prusa warns that leftover IPA combined with liquid resin may create white stains on cured objects.
4. Not cured long enough for the partCommon
   Formlabs says to increase post-curing time for thick, bulky parts because they are slower to heat. Prusa says that if an object is still sticky after its dry-and-cure cycle, you can run the process again until the result is right.
5. Resin-specific post-processingOccasional
   Some resins need a different wash or cure procedure. Formlabs, for example, gives one flexible resin an instruction to cure it submerged in water. Use the procedure your resin's maker publishes for that resin.

Fix it, one change at a time

1. Wear gloves and eye protection for every step. A tacky surface is uncured resin, which the SDS classes as a skin sensitizer and, depending on the resin, an eye irritant or a cause of serious eye damage.
2. Wash again in clean solvent, using the solvent and time your resin maker specifies. Give recesses, hollow parts and internal channels extra attention.
3. Do not fix it by soaking for a very long time. Formlabs warns that excessive solvent exposure affects part quality, and Prusa says over-washed objects may develop tiny cracks, even a day later.
4. Let the part dry completely before curing, until no solvent remains on or inside it.
5. Cure again following the resin maker's cure settings, giving thick parts more time. Formlabs says over-curing is acceptable for its materials unless stated otherwise, and Prusa says curing multiple times is fine on its CW1; check your resin's own guidance.
6. Replace the wash solvent when it no longer cleans well, and handle the used solvent as hazardous waste under your local rules; for resin-soaked paper, see the waste lesson. See Resin Waste and Disposal.

Confirm it is fixed

After drying and curing, the part is dry to the touch on outside faces and in recesses, does not hold a fingerprint, and shows no white streaks. If only one stubborn area is tacky, wash and cure that part again rather than extending every cycle.

Why it happens

A print fresh off the platform is coated in liquid resin and is only partly cured. Washing removes the liquid; curing finishes the reaction in the solid part. A tacky surface means liquid resin was still on the part when it was cured, or the cure did not finish the surface.

Washing works by dissolving resin into the solvent. As the bath fills up with dissolved resin, it gets worse at carrying more away, and eventually it leaves a thin film of resin behind on every part. That film then cures poorly, or not at all, which is why a tired bath gives parts that are sticky everywhere. Shapes that hold liquid, such as cups, hollows and channels, need more time and movement for fresh solvent to reach them.

Solvent left on the part causes a different problem. Prusa warns that leftover alcohol mixed with resin can leave white stains on the cured surface. Drying first, until the part is free of solvent, avoids that.

Curing has to reach the whole part. Thick parts warm slowly in a heated curing unit, and resin makers publish time and temperature for each resin. There is no single cure time that suits every resin; use your resin maker's table and adjust only for part size as they describe. See Washing and Curing Resin Prints.

Until a part is fully cured, treat it like liquid resin: gloves on, no contact with skin, and keep resin-loaded solvent out of drains. The Grey Resin SDS, for example, says not to discharge the product into public wastewater and classes it as toxic to aquatic life. Water-washable resins are not drain-safe either; follow their own SDS. See Resin PPE.