What are the mandatory steps in resin post-processing?
Resin post-processing has three mandatory steps: washing the print with isopropyl alcohol to remove uncured liquid resin, drying it completely, and UV curing it to finish the polymerization process. Support removal, sanding, and painting are optional depending on the finish you're after.
When you pull a print off the build plate, it's far from finished. After printing, post-processing always follows the same sequence: first you wash the model to remove excess uncured resin, then you cure it to complete the polymerization — which is only partial during the actual print. Skipping either of these steps ruins the result: a poorly washed print cures with blotches and loses detail, while an uncured print stays soft, tacky, and potentially toxic to handle.
The basic workflow you'll repeat with every batch looks like this:
- Washing: dissolving residual liquid resin with high-purity isopropyl alcohol (IPA).
- Drying: letting all the alcohol evaporate before exposing the print to UV light.
- Support removal: ideally done while the print is still green, before final curing.
- UV curing: hardening the print under 365–405 nm light.
- Optional finishing: sanding, priming, painting, and varnishing.
The first three steps are non-negotiable if you want a safe, dimensionally accurate print. Finishing depends on the end use: a functional prototype can stop at curing, while a display miniature calls for the full workflow. Here are post-processing products to cover every stage.
How to properly wash a freshly printed resin part
To wash a freshly printed resin part, submerge it in 95% or higher isopropyl alcohol for 3–5 minutes, agitating gently and using a soft brush on recessed areas. Use a two-bath system: one "dirty" bath to remove the bulk of the resin, and a clean rinse bath for the final wash.
Isopropyl alcohol works because resin used in most resin 3D printers — typically based on methacrylates or acrylic esters — isn't water-soluble, but it is soluble in alcohol. That's why IPA is the go-to solvent. Concentration matters: you need alcohol above 95% purity, or your print will turn white after washing and curing. For this we use 99.9% isopropyl alcohol for resin washing, which stays usable longer before becoming saturated and leaves less residue behind.
The two-bath system is the single best way to get more mileage out of your IPA. Keep two separate containers: wash the print in the first one, which removes the bulk of the liquid resin, then transfer it to the second for a final agitated rinse to clear any remaining residue. Watch your soak time — 3 to 5 minutes is the general guideline; extended soaking can make prints brittle.
One key safety and quality tip: wash your prints before removing supports. For hollow pieces or parts with internal channels, use a syringe to remove any trapped resin. IPA is flammable, so always work with nitrile gloves and proper ventilation. If you'd rather automate the entire process, wash and cure stations place the print in a rotating basket inside the alcohol container, then cure it in the same machine.
How Long Does Each Resin Type Need to UV Cure?
UV curing in a dedicated station typically takes just a few minutes for standard prints: clear and transparent resins cure the fastest, water-washable and dark resins take a bit longer, and flexible resins are the slowest of the bunch. Keep in mind these are ballpark figures — larger prints and darker colors will always need more time.
Resin color is the factor that catches most beginners off guard. Clear and transparent resins allow UV light to penetrate deeper, resulting in faster, more even curing. Black and very dark resins absorb most of the light at the surface, so curing the entire model can take several minutes longer. As a general guide: water-washable resins tend to cure more slowly than alcohol-based ones — roughly 3–5 minutes versus 2–3 minutes for standard resins — and flexible resins take the longest, often requiring 6–8 minutes or more.
These numbers are guidelines, not hard rules. Many factors affect curing time, including print size, geometry, UV wavelength, resin type, and ambient temperature, so you'll need to adjust accordingly. Finding the sweet spot takes some trial and error. To check whether a print is fully cured, look for a smooth or matte surface — that's a good sign. You can also do a tap test: drop the print on a hard surface, and a clear, solid sound like a stone means it's done. An undercured print will look wet and feel tacky.
Overcuring is just as much of a problem: it makes prints brittle and prone to cracking, and clear or transparent resins are especially likely to yellow if overcured. Don't leave a print in the station for half an hour "just to be safe." One important safety note before curing: never use a heat gun or hair dryer on prints that still contain alcohol — this is a fire hazard. Let them air dry or use a gentle blast of cool air instead.
| Resin Type | Typical Cure Time (UV Station) | Notes |
|---|---|---|
| Standard / alcohol-based | 2–3 min | Fast, even cure |
| Clear / transparent | 2–3 min | Light penetrates easily; watch for yellowing if overcured |
| Water-washable | 3–5 min | Generally needs more time than alcohol-based resins |
| Dark colors (black/navy) | Longer; rotate frequently | Pigment blocks UV penetration |
| Flexible | 6–8 min or more | Slowest resin type to fully harden |
How to Remove Supports Without Damaging Your Print
Remove supports while the print is still in the "green" state — after washing but before final UV curing — because the partially cured resin is softer, so supports snap off more cleanly with less risk of breaking or leaving marks. If the geometry is delicate or prone to warping, wait until after curing and cut supports with flush cutters while wearing safety glasses.
This is one of those decisions where manufacturer theory and real-world practice collide. You should remove supports before curing because uncured resin is far softer than cured resin, making the job much easier — removing supports from fully cured prints tends to leave more marks and risk snapping important parts of the model. In many cases, warm water is all you need: run the print under lukewarm water and gently pull the supports away; they should release cleanly without causing damage.
So why do manufacturers recommend the opposite? Safety and dimensional stability. Manufacturers prioritize safety and legal liability, recommending post-cure support removal so users only handle fully polymerized, non-toxic plastic. There is a technical nuance worth knowing: on solid, self-supporting geometries where the internal mass naturally resists deformation, green removal is preferable to protect the surface finish from chipping. On thin or warp-prone parts, curing with supports still attached reduces the risk of distortion.
If you choose to remove supports after curing, do it carefully: cut them with flush cutters or sprue cutters, and always wear safety glasses — cured resin fragments fly across the room when clipped. My practical recommendation: for miniatures and figures, remove supports green almost every time; for large functional parts or thin-walled prints, cure first.
How to Sand and Prep a Resin Print for Painting
To prep resin for painting, sand progressively without skipping grits: start with 200–400 to remove support marks, work up to 600–800, and switch to wet sanding from 400–600 onward to prevent dust and heat buildup. Clean the surface between every grit change and again before priming.
The key is respecting the grit progression. Jumping straight from coarse to fine sandpaper leaves deep scratches that become even more visible after painting or polishing; instead, work through intermediate grits gradually (for example 150 → 220 → 400 → 600+) to maintain a consistent surface texture. For resin, Anycubic suggests a reasonable starting range: 200–500 grit for initial sanding to remove major imperfections, followed by 600–800 grit for a finer, polished surface finish.
Wet sanding is not optional once you reach the finer grits. Water acts as both a lubricant and a coolant, preventing the sandpaper from clogging — which happens when resin dust melts into the abrasive and renders it useless. Keeping the surface wet continuously flushes away residue and produces a smooth, satin finish rather than a scratched one. For most of what I work on, wet sanding to 600 grit is more than enough; going beyond that is chasing a polish only you will notice under a magnifying glass.
Two important warnings. First, your health: always wear a respirator when sanding cured resin, as the dust particles are fine and harmful when inhaled. Second, clean between stages: skipping the cleanup between sanding grits causes cross-contamination — coarser grit dust or particles can scratch the surface during fine sanding and undo all your progress.
What Finishing Products Should You Use? (Primer, Varnish, Paint)
Resin finishing follows three layers: primer to create adhesion and reveal flaws, paint applied in thin coats over a dry base, and a final varnish to seal and protect. Always apply thin coats and allow each one to dry completely before moving on.
Primer does two jobs at once: it creates a uniform surface for paint to bond to, and it reveals any imperfections you may have missed during sanding. Application technique makes all the difference between a plastic-looking finish and a quality one — use a "dusting" technique, applying two or three light coats from about 8 inches (20 cm) away rather than one heavy coat. This prevents primer from pooling and obscuring fine details like rivets or panel lines. Browse our resin primers available in a range of base colors.
On primer color: primer comes in several colors, most commonly white or neutral shades like gray. If you're choosing between white and gray, go with gray if your topcoat is also gray — but in general, a lighter color is the safer choice since it reduces the risk of bleed-through affecting your final paint. After priming, inspect the piece again: if you can still see obvious surface flaws, go ahead and give it another light sand.
Paint follows the same thin-coat philosophy, always letting the primer cure fully before you start. To seal the finished piece, use a finishing varnish — it protects the paint from wear and gives you your desired sheen level, whether matte or satin. One classic mistake worth avoiding: don't paint in high humidity. Moisture in the air causes aerosol sprays to "blush," leaving a milky, cloudy finish. Wait for a dry day.
When Is It NOT Worth Post-Processing and Better to Just Reprint?
Post-processing isn't worth it when the print failed at the source: perforated walls from a printing failure, layer shifts, lost detail from inadequate washing, or structural parts that are over-cured and brittle. In those cases, reprinting costs less time and resin than patching a defect that will still show through in the end.
Some defects can't be fixed by post-processing — they can only be partially hidden. If a miniature lost fine detail because the wash alcohol was saturated and the resin cured with a scaly residue, sanding won't bring back detail that's simply no longer there. Those fine white flakes are a telltale sign that your isopropyl alcohol is no longer concentrated enough and has been used too many times. In this case, reprinting with fresh IPA is the faster path forward.
Typical scenarios where I reach for a reprint instead of a rescue:
- Shifted layers or delamination: adhesion or exposure failures can't be fixed by sanding.
- Overcured and brittle print: if it's already fragile, any handling will snap it.
- Lost fine detail: support marks on the visible face of a mini usually cost more to fill than to reprint with better support placement.
- Wall sanded through: if you breach the wall, you'll need to patch with UV resin and sand again — and it's rarely worth it.
The rule I always go back to: if the defect is surface-level and the geometry is intact, post-process without thinking twice. But if it touches the structure or the detail that gives the print its character, I reprint — no regrets. I say this plainly because I've spent entire afternoons trying to rescue prints that were doomed from the start, only to throw them out anyway. Relaunching with corrected settings almost always costs less time than heroic patching.
Visual workflow: from the build plate to finished print in 7 steps
This is the complete, step-by-step process you repeat for every print you want to bring to display quality:
- Remove the print from the build plate. The sooner you work on it, the better — the longer you leave it, the more it will cure from ambient light, making support removal harder.
- First wash in "dirty" IPA. Submerge for 3–5 minutes in 95%+ isopropyl alcohol, agitating and brushing into recesses.
- Second wash in clean IPA. Rinse in fresh alcohol to remove any remaining residue. Some prints need two full wash cycles for a thorough clean.
- Remove supports while green. Pull them off gently under warm water while the resin is still soft; leave any marked spots to sand after curing.
- Dry completely. Let all the alcohol evaporate before UV curing. Never apply heat while solvent is still present.
- UV cure. 2–6 minutes depending on resin type, color, and size — rotate the print for even exposure. Sanding after curing is the better approach: fully cured prints are stronger and hold their shape during sanding, though sanding before curing is possible if you work carefully with the softer resin.
- Finishing: sand, prime, paint, and varnish. Progressive wet sanding, thin coats of primer, painting, and a sealing topcoat.
A practical note on the wash–supports–cure order: there are two valid schools of thought. The manufacturer approach (cure before removing supports, for stability and safety) and the modeler approach (supports while green, for a cleaner finish). Choose based on the print, not out of habit.
Frequently asked questions
Can I reuse isopropyl alcohol after washing resin prints?
Yes. If the alcohol becomes increasingly milky and resin-saturated, you can clean it with UV light: the dissolved resin cures and precipitates out, and you can then reuse the filtered alcohol. Leave the container in sunlight or under a UV lamp, let the resin solidify at the bottom, and filter it out. Done this way, a single bottle lasts a surprisingly long time before it needs to be disposed of.
What concentration of isopropyl alcohol is best for washing resin prints?
The purer, the better. For washing 3D resin prints, 99% isopropyl alcohol is ideal. Below 95%, residual water can cause the print to turn chalky or white after curing. A 99.9% IPA also saturates more slowly, so you get more washes per bottle.
Why is my resin print still sticky after washing and curing?
It's usually dirty alcohol or insufficient cure time. If your print stays tacky after washing with IPA, don't panic: 90% of the time it's dirty or saturated alcohol. The fix is to re-wash in fresh IPA, dry thoroughly, and add more UV exposure time.
Is uncured resin dangerous?
Yes, treat it with respect. Liquid resin is toxic; tacky spots on a print contain uncured liquid resin, which makes them potentially toxic and something you want to avoid — and that's exactly what proper washing and curing prevents. Always wear nitrile gloves when handling uncured prints and work in a well-ventilated area.
Do I absolutely need a wash and cure station?
Not strictly, but it saves time and improves consistency. Tools like a wash and cure station or an ultrasonic cleaner make post-processing easier; they're convenient but not required if you follow good practices with basic containers. For high-volume printing they're worth every penny; for occasional use, two jars of isopropyl alcohol and a UV lamp will get the job done.
That said, if you're printing every week you'll end up buying a station anyway — not because you have to, but because shaking jars of IPA by hand at eleven on a Sunday night gets old fast. I stuck with two mason jars and a UV flashlight for quite a while, until I'd had enough.
Should you wash again after sanding and before priming?
Yes, and it's a step a lot of people skip. Sanding without washing first is a mistake: oils from handling prevent primer from adhering properly, so wash your prints with warm soapy water and let them dry completely before priming. After fine sanding, wipe away all dust with a clean cloth or compressed air so the primer goes on evenly.
Let the creativity flow 😎
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