ABS & ASA 101 + Acetone Vapor Smoothing: A Safe, Simple Guide

PLA and PETG are great for everyday prints. But when you need heat resistance, outdoor durability, and a glossy, near-injection look, it’s time to reach for ABS or ASA—and finish them with acetone vapor smoothing.

Below is the full guide: what to buy, how to do it safely, and exactly how long to cook parts for a glassy finish without melting detail.

Why ABS/ASA (vs. PLA/PETG)

• Tougher & more heat-resistant: Better for props, armor, and parts that see the sun or a hot car.

• ASA > ABS outdoors: ASA handles UV better; it won’t yellow or get brittle as fast.

• Acetone reactive: Both ABS and ASA respond to acetone vapor, letting you smooth layer lines to a glossy, paint-ready surface.

Safety First (read this)

Printing ABS/ASA and working with acetone isn’t the PLA world:

• Fumes/VOCs: Print in a ventilated area or enclosure with filtration. Don’t run ABS/ASA next to your bed or in a closed room.

• Acetone: Flammable and can irritate skin/eyes/lungs. Use PPE: respirator (organic vapor cartridges), gloves, eye protection.

• Chamber material: Use a polypropylene (PP) bin—acetone can dissolve other plastics.

• No sparks/open flames anywhere near the setup.

If you’re not sure—don’t guess. Ventilate, mask up, and keep a fire extinguisher nearby.

What You Need (about $50)

• Polypropylene storage bin with lid (clear, latching; look for PP recycling mark)

• Paper towels (enough to line walls)

• Metal grate/stand to keep parts above the bin floor

• Acetone (hardware store)

• Timer (phone is fine)

• PPE: respirator (OV cartridges), nitrile gloves, eye protection

Optional but useful: small binder clips (to hang towels), extra PP bin for larger armor pieces.

Print Settings That Help Smoothing

• Material: ABS or ASA (ASA for outdoor props)

• Layer height: 0.16–0.24 mm

• Walls: 3–4 perimeters (smoothing thins edges slightly)

• Top/Bottom: 5–7 layers

• Infill: 15–25% is plenty for armor shells

• Bed/Enclosure: Enclosed printer or DIY enclosure; moderate bed temps to prevent warping

• Cooling: Minimal for ABS/ASA; keep drafts away

Step-by-Step: Acetone Vapor Smoothing

Location: Garage or outdoors with good airflow.

1. Line the bin

   • Place a few dry paper towels on the bottom.

   • Set the metal grate on top so your part sits above any liquid.

2. Soak the walls

   • Fold paper towels, drizzle a small amount of acetone onto each (don’t drench), then unfold and hang/press them along the inner walls of the bin.

   • You want vapor, not puddles. If a towel drips, reduce acetone.

3. Set the part

   • Place your clean, dust-free print on the grate. Avoid touching with bare hands (oils print through).

4. Close & time it

   • Put the lid on. Start with:

     • Fine parts / high detail: 8–12 minutes

     • Medium shells (mask/gauntlet): 12–20 minutes

     • Thicker armor plates: 20–30 minutes

   • Peek quickly if you must, but every open loses vapor.

5. Cure

   • Remove the part and let it cure 12–24 hours (ventilated spot). It’ll be tacky at first; don’t touch the glossy surfaces.

6. Iterate if needed

   • After curing, you can run another cycle to push more gloss. Never “overcook”—details can soften.

Sanding: Before vs. After (what actually works)

• Pre-sand then smooth (glossy final look):

  • Quick pass 220 → 400/600 wet.

  • Vapor smooth brings back the shine. Great when the smooth plastic finish is your end look (no paint to chip).

• Smooth then post-sand (for paint):

  • Vapor smooth → 220 → 400/600 wet.

  • Kills the shine but leaves a super-flat, paint-ready surface. Best for color coats and metallics.

• Metallic paints show sins:

  • Bright/reflective coats magnify tiny ripples. Matte or textured finishes hide more.

How Long To Cook? (Quick table)

Part TypeWall/DetailFirst PassNotesSmall greeblies / emblemsFine8–12 minWatch edges—details soften fastMask/gauntlet shellsMedium12–20 minMost cosplay parts live hereLarge armor platesThick20–30 minBetter to do two shorter passes than one long one

Rule: Stop when the surface looks uniformly satin-glossy. Over-gloss = softened detail.

Common Problems & Fixes

• Rippled finish / visible lines after smoothing
  → Do a light pre-sand next time; try a second short pass after full cure.

• Orange peel / texture
  → Too much liquid acetone pooled. Use less on towels; ensure no drips.

• Blurry edges / lost detail
  → Overcooked. Cut time by 30–50% and do two short passes.

• Sticky after hours
  → Let it cure longer in fresh air. Warm, dry airflow helps.

• Cracking/warping during print
  → Enclose the printer, reduce drafts, tune temps, increase chamber warmth, and slow outer walls.

When to Choose ABS vs. ASA

• ABS: Cheaper, easy to source, smooths great; okay indoors, can yellow outdoors.

• ASA: Similar smoothing, UV-resistant, better for helmets/props that see sunlight.

FAQ

Can I smooth PLA or PETG with acetone?
No. Standard PLA/PETG don’t respond to acetone like ABS/ASA.

Will smoothing weaken my part?
Edges soften slightly. Use extra perimeters on structural areas if you plan to smooth.

Is one long pass better?
No. Two shorter passes with full cure in between keep details sharper.

FAQ

Can I smooth PLA or PETG with acetone?
No. Standard PLA/PETG don’t respond to acetone like ABS/ASA.

Will smoothing weaken my part?
Edges soften slightly. Use extra perimeters on structural areas if you plan to smooth.

Is one long pass better?
No. Two shorter passes with full cure in between keep details sharper.

The Bottom Line

ABS and ASA unlock stronger, heat-tolerant, outdoor-ready prints—and acetone vapor smoothing delivers that pro, glossy finish fast. Respect the safety, run conservative times, and decide up front: gloss plastic finish (pre-sand → smooth) or paint-ready flat (smooth → post-sand).

Quick-Ref Card (print this)

• Bin: Polypropylene (PP) only

• PPE: Respirator (OV), gloves, eye protection

• Timing: 8–30 min depending on part size

• Finish path:

  • Gloss plastic: Pre-sand → Smooth

  • Paint-ready: Smooth → Post-sand

• Cure: 12–24 h before handling/second pass