5
Techniques
Print finishing
Post-processing
A practical overview of finishing techniques for 3D prints, from fast sanding to chemical smoothing and paint-ready prep.
When to use post-processing
Use it when you want to hide layer lines, prepare the surface for paint, improve visual quality, or bring a model to presentation level.
30
Total steps
6.0
Steps / technique
Workflow
Preparation
Sanding and filler
Smoothing
Chemistry, UV resin, or wet sanding
Paint
Primer, basecoat, details
Protection
Clearcoat and curing
What is your goal?
Hide layer lines
Unify the surface without losing shape
Prepare for paint
Create a stable base for primer and paint
Showroom gloss finish
Target a highly polished presentation look
Quick functional finish
Get practical results in minimal time
Abrasion resistance
Improve durability for frequent handling
By material
PLAPETGABS/ASAResin printTPU
PLA
What to recommend
- • Use wet sanding with finer grits, then apply primer/filler.
- • Use multiple thin coats instead of one heavy layer.
What to avoid
- • Avoid aggressive chemical smoothing without sample testing.
Risks
- • Overheating while sanding can soften the surface.
Troubleshooting
Sticky surface after UV resin
Cause
Insufficient curing or overly thick application.
Fix
Clean with IPA and re-cure in shorter cycles.
Prevention
Apply thin coats and rotate the model while curing.
Yellowing after curing
Cause
Over-curing or prolonged UV exposure.
Fix
Lightly sand and return to thin controlled coats.
Prevention
Use controlled curing times and suitable resin.
Detail loss after a thick layer
Cause
Excess filler or UV coating thickness.
Fix
Local re-sanding and continue with thin layers.
Prevention
Inspect continuously under side lighting.
Quality checklist
✓Surface is clean, dry, and free of loose dust.
✓Side-light inspection shows no major waves or deep scratches.
✓Surface is not sticky and shows no local over-curing.
✓Paint adhesion was verified in an inconspicuous area.
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Required equipment
Spray primer / filler (recommended: Motip Plastic Primer or Tamiya Surface Primer)Acrylic putty or body filler for small defectsSandpaper: 220, 400, 600 gritSpray surface (cardboard, stand)Respirator filter for organic vapors (for spray primer)Protective gloves and goggles[OPTIONAL] Masking tape (to protect untouched surfaces)
Recommended workflow
- 1First remove larger defects and lightly sand the whole model with 220 grit.
- 2Apply the first thin layer of filler primer from a distance of about 20-25 cm.
- 3After drying, inspect where grooves and uneven spots are still visible.
- 4Apply local putty to problematic spots and sand them with 400 grit after drying.
- 5Add a second thin primer layer and lightly level the surface with 600 grit.
- 6If needed, repeat one more layer until the surface is uniform.
Pro tip
Use multiple thin coats instead of one heavy layer. The finish will be smoother and less prone to runs.
Safety
Use spray products outdoors or in a well-ventilated space. A vapor respirator, gloves, and goggles are essential.
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Required equipment
Sandpaper: 120, 220, 400, 800, 1200, 2000 gritContainer with water (for wet sanding)Sponge sanding block or cork blockMicrofiber cloth for dryingSafety goggles and dust mask (for dry sanding)[OPTIONAL] Plastic polish or automotive wax (for final gloss)
Recommended workflow
- 1Start with coarser grit 120-180 and remove support marks and major uneven areas.
- 2Move to 220 and begin wet sanding so the paper does not clog and the surface does not tear.
- 3Continue with 400 -> 800, rinse the model after each step, and check for scratches.
- 4Finish with 1200 -> 2000 using light pressure for a smooth satin-gloss surface.
- 5For final shine, apply polish or wax with a microfiber cloth.
- 6At the end, inspect the model under side light and step back one grit if needed.
Pro tip
For complex shapes, use a small tool or softer sponge. For flat faces, always use a sanding block for a more even and faster result.
Safety
Dry sanding produces fine dust, so wear a respirator and goggles. Prefer wet sanding and a ventilated area whenever possible.
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Required equipment
Clear UV resin (365-405 nm) compatible with manual curingUV lamp 365-405 nm or cure station (sunlight only as emergency backup)Nitrile gloves, safety goggles, respirator for organic vaporsSoft silicone brush / foam applicator / disposable brushIPA 95%+, lint-free paper towels, silicone mat[OPTIONAL] Stand or rotating base for uniform lighting
Recommended workflow
- 1Lightly sand the surface (about 400-800), remove dust, and degrease with IPA.
- 2Apply a very thin UV resin coat, avoiding buildup in seams.
- 3Let the surface level for 1-2 minutes and wick away drips with a brush.
- 4Pre-cure with short UV cycles (about 20-40 s per side) while rotating the model.
- 5Then run the main cure around the full model in several short passes.
- 6If still rough, apply a second thin coat and repeat.
Pro tip
Multiple ultra-thin coats are always better than one thick layer. You preserve detail and reduce yellowing risk.
Safety
Handle uncured resin only with gloves, goggles, and ventilation. Do not aim UV light into your eyes and prefer short curing cycles.
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Required equipment
Primer coat - required base for paint adhesionAcrylic paints (recommended: Vallejo, Citadel, Tamiya) for hand paintingAirbrush or spray paints for area coverageFlat and round brushes sizes 0, 1, 2, 4 (for detail and larger surfaces)Palette and thinner for acrylic paints (distilled water or Vallejo Thinner)Clearcoat - matte, satin, or gloss based on desired effect[OPTIONAL] Tamiya masking tape or blue tape for clean edges
Recommended workflow
- 1Apply a thin primer and let it dry properly; paint adhesion is poor without it.
- 2Apply base color in 2 thin coats instead of one heavy coat.
- 3For detailed models, use a wash to emphasize recesses and depth.
- 4For edge highlights, use a light drybrush with a brighter color.
- 5Paint small details and use masking tape for crisp transitions.
- 6Finish by sealing with clearcoat according to the target effect (matte/satin/gloss).
Pro tip
If possible, use an airbrush or multiple thin brush coats. The color will look cleaner and avoid rough marks.
Safety
Use paints and lacquers with ventilation and away from ignition sources. For routine use, water-based acrylics are usually the safest option.
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Required equipment
Acetone (for ABS/ASA) or Ethyl Acetate (for PLA) - pure technical gradeSealed glass or metal container with lid (not plastic - acetone dissolves it)Aluminum foil to place the model on a raised platformProtective gloves (nitrile, not latex), goggles, and a respirator for organic vaporsVentilated room or fume hood[OPTIONAL] Brush for application (alternative to vapor method)[OPTIONAL] Stand or wire for hanging the model
Recommended workflow
- 1Place a small amount of solvent (about 5-10 ml) into a glass or metal container.
- 2Position the model above the vapor level, not directly in the liquid, and close the container.
- 3Let it act for 5-15 minutes and check every 2-3 minutes.
- 4After removal, place the model on a clean surface and do not touch it for 30-60 minutes.
- 5After full hardening, evaluate the result and repeat with a shorter cycle if needed.
- 6As an alternative, apply a very thin layer with a brush for local touch-ups.
Pro tip
For PLA, UV resin or epoxy coating is usually more predictable than acetone experiments.
Safety
Work only in a ventilated area, with gloves and eye protection. Solvents are flammable, so keep all flames, sparks, and hot surfaces away.