How to Smooth PLA and PETG 3D Prints (What Actually Works)
PLA and PETG are two of the most popular 3D printing materials, but both tend to show visible layer lines after printing. While they look similar, they behave very differently when it comes to smoothing. This guide explains how to smooth PLA and PETG prints using methods that actually work, without unnecessary chemicals or risky shortcuts.
If you’re coming from ABS finishing, it’s important to know upfront: PLA and PETG cannot be acetone smoothed. Instead, they rely on mechanical and surface-based finishing techniques.
How to Smooth PLA 3D Prints
PLA is relatively easy to finish, but it does not react to acetone or common solvents. The safest and most reliable way to smooth PLA is through controlled sanding combined with surface coatings.
Best methods for smoothing PLA
- Sanding: Start with 150–220 grit to remove layer lines, then progress to 400–800 grit for a smoother surface.
- Filler primer: Spray filler primer fills small gaps and layer lines, reducing sanding effort.
- Fine sanding: Light wet sanding at 1000–2000 grit improves surface finish before painting.
- Optional coatings: Epoxy or surface sealers can be used for display parts.
Important: Acetone does not smooth PLA. Using it can damage the surface rather than improve it.
PLA smoothing tips
- Use light pressure to avoid flattening details
- Let primer fully dry before sanding
- PLA softens easily with heat — avoid aggressive heat guns
PETG Smoothing: What Works and What Doesn’t
PETG is tougher and more chemically resistant than PLA, which makes PETG smoothing more limited. Chemical smoothing does not work, but PETG can still be finished to a clean, professional look.
Effective PETG smoothing methods
- Sanding: Works well, but PETG may feel “gummy” at low grits — move gradually.
- Wet sanding: Reduces heat buildup and improves consistency.
- Surface coatings: Primer or epoxy coatings are effective for cosmetic parts.
Methods to avoid with PETG
- Acetone or solvent smoothing (no reaction)
- Aggressive heat polishing (high risk of warping)
PETG requires patience, but with careful sanding and coating, it can achieve a smooth, durable finish.
PLA vs PETG Smoothing Comparison
| Method | PLA | PETG |
|---|---|---|
| Sanding | ✅ Excellent | ✅ Good |
| Filler primer | ✅ Very effective | ✅ Effective |
| Acetone smoothing | ❌ No | ❌ No |
| Heat smoothing | ⚠️ Limited | ⚠️ Risky |
Safety Notes
Even without solvents, smoothing creates fine dust and fumes. Always sand in a ventilated area, wear eye protection, and use a respirator when spraying primers or coatings.
Final Thoughts
If you’re wondering how to smooth PLA, sanding combined with filler primer is the safest and most reliable method. For PETG smoothing, sanding and surface coatings are your best options. Neither material benefits from acetone smoothing, and trying to force chemical methods usually causes more damage than improvement.
With patience and the right approach, both PLA and PETG prints can be finished to look clean, professional, and ready for real-world use.
Frequently Asked Questions
Can you acetone smooth PLA?
No. Acetone does not chemically smooth PLA and can damage the surface.
Can PETG be chemically smoothed?
No. PETG is chemically resistant to acetone and common solvents.
What is the easiest way to smooth PLA?
Sanding followed by filler primer is the easiest and most beginner-friendly method.