The Best Way to Smooth 3D Prints (No Sanding)

Summary

JanTec Engineering tests chemical smoothing as a way to reduce visible layer lines on FDM 3D prints. The video covers ABS, ASA, PVB, PLA, and HIPS, comparing application methods and considering appearance, fit, scratch resistance, and layer adhesion. Surface quality is judged visually under studio lighting rather than measured with a roughness instrument.

How chemical smoothing works

A compatible solvent softens a print’s outer surface into a thin, liquid-like layer. Surface tension helps level the layer lines; when the solvent evaporates, the plastic hardens again with a smoother finish. Unlike heating the part, this treatment is intended to affect mainly the outer skin, reducing the risk of softening the whole model.

The host advises wearing a respirator and gloves and remembering that most of the chemicals used are flammable.

Material tests and findings

• ABS and ASA with acetone: ABS and ASA can be smoothed because they contain styrene-based material that is affected by acetone. The host placed acetone-soaked paper towels in a sealed, acetone-resistant chamber without letting them touch the parts. About one hour produced very glossy chess pieces, though sharp features such as rook corners lost definition. A second, roughly two-hour treatment smoothed technical mounts, but the fit changed enough that a rod glided worse afterward, despite the smoother surface. The host warns that mechanical parts may need tolerance adjustments.
• Scratch resistance and strength: Smoothed ABS felt softer, and marks from a screwdriver and cutter were visible. A protective coating may be worth considering. The host also cites Prusa lab tests reporting roughly doubled layer adhesion compared with untreated samples, suggesting a potential strength benefit alongside the cosmetic effect.
• PVB with IPA: PVB can be softened with isopropyl alcohol and is printable in a manner similar to PLA. The host tried vapor smoothing with IPA-soaked towels, brushing IPA directly onto a part, and briefly dipping a part. Results were mixed: some surfaces became smoother, but translucency made infill visible, and brushing appeared less effective than vapor treatment. The host recalls getting better results previously by spraying IPA and notes PVB may work better for vase-mode prints without infill.
• PLA with Playglue: Playglue is presented as a specialized smoothing agent for PLA, though the host says it was not yet widely available worldwide. The two tested application approaches were shaking small parts in the liquid for 10–30 seconds and brushing it on. Both can be awkward: softened parts are easy to mark while removing them from a jar or setting them down to dry. After two days, brushed areas showed a clear reduction in layer lines. The host sees promise in PLA smoothing if the product becomes more available and affordable.
• HIPS: HIPS is also polystyrene and can be smoothed with acetone; it can additionally dissolve in limonene. The video does not show a HIPS smoothing test.

Overall recommendations

The host considers acetone vapor smoothing of ABS or ASA the most reliable, cost-effective, and consistent option in these tests. PVB is a possible alternative when printing ABS is impractical, though the results shown were less consistent. For PLA, a dedicated product such as Playglue may be worth trying, with care taken to handle and dry parts without damaging the softened surface.

The video is the first installment in a three-part series. The host says the next videos will cover designing and slicing to make layers less visible, followed by mechanical sanding with filler and primer.

Main speaker and sources

• Main speaker: The JanTec Engineering host, presenting the tests and conclusions.
• Other sources mentioned: Prusa Research is cited for laboratory results on layer adhesion and a blog article about smoothing PVB. PCBWay is identified as a sponsor of part of the video; Prusa Research sponsors the host’s studio.