3D print post-processing methods: vapor smoothing

Vapor smoothing is a technique for improving the surface finish of 3d-printed parts. It uses acetone vapor to smooth the surfaces of ABS prints, removing the layer lines that result from the printing process. We don’t typically use vapor smoothing at Nervous System because we 3D print in nylon via Selective Laser Sintering (you can read about how we tumble finish those pieces in this blog post). However, we do occasionally 3D print in ABS on our Makerbot, so we decided to test out vapor smoothing for ourselves. We were curious to see how the process would work on articulated 3D prints like our Kinematics@Home designs and 2-color prints like our reaction-diffusion animals.

vapor smoothing interlocking parts

Vapor smoothing works because ABS plastic dissolves in acetone. We were worried that interconnected parts, like our Kinematics bracelets, would become glued together during the smoothing process. However, this turned out not to be the case. While the motion of the smoothed Kinematics bracelet is “stickier” than its unsmoothed counterpart, it still moves freely.

We found that timing is particularly critical for pieces with joints and moving parts. With 20 to 30 seconds of exposure, Kinematics pieces retain their ability to move and get a shiny surface finish. However, any longer than that and the integrity of the joints will degrade, melting the pieces into each other and causing the moving parts to stick.
a vapor smoothed kinematics bracelet

vapor smoothing dual extrusion prints

We were also curious how our dual-extrusion designs would survive the smoothing procedure. Would melting the surface cause our precise, 2-color designs to become muddled?


We were pleased to see that we were able to get a smooth surface finish without the colors bleeding into one another. Through trial and error, we found that there was no visible benefit for acetone exposure to exceed 30-40 seconds.

raw vs polished
raw vs polished
a shiny vapor smoothed 2-color octopus
a shiny vapor smoothed 2-color octopus

more information

For a more in-depth look at the setup and process that we adhered to, check out this tutorial and this blog post. Please note: Acetone vapor is hazardous! Vapor smoothing should be performed in a well-ventilated area and with an appropriately rated respirator.

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