Vapor treated part and untreated partAcetone vapor treated part and untreated part

Using an acetone vapor bath to treat ABS 3D-printed parts is an extremely effective (and only moderately dangerous) way to create parts with a shiny, smooth finish. Applying acetone with a brush, or submerging a model in a liquid acetone bath, generally results in a part that has had its detail completely melted away. Using acetone vapor helps preserve detail while giving a smooth and shiny finish.

The boiling point of acetone is 132.8°F, but it will evaporate at room temperature. There have been experiments using acetone vapor at room temperature, but they can take up to 40 minutes to smooth a part. Using a boiling acetone vapor process can smooth a part in less than 10 seconds! Borrowing a technique from a moonshiner I’d met, I used a water bath to keep the acetone at a steady 140°F.

Materials needed (bonus hidden cat)Materials needed (bonus hidden cat)

SAFETY FIRST! Acetone vapor is highly flammable, and definitely not something you want to be breathing in. Make sure you do this in a well-ventilated area.

Materials needed:
Desk-clamp light
Desk fan (ventilation is very important when using acetone vapor)
Electric range stove
Nylon fishing string
Mason jar
Cloth rag
Thermometer (with non-ABS plastic wire jacket on thermocouple)
Aluminum foil

The UP! Mini 3D printer is capable of printing down to .2mm layer height, which creates very fine layers that look relatively smooth when printed at the ‘FINE’ quality setting. For this experiment, I used .2mm layer height, ‘FINE’ quality setting, and Octave Black 1.75mm ABS. The model used is an Owl Statue uploaded to Thingiverse under a Creative Commons Attribution license.

The first step is setting up your apparatus. The desk-clamp light is used to suspend the part above the acetone vapor jar. Put a few inches of water in the pot, placing a rag at the bottom to sit the mason jar on. Fill the jar with acetone until it is about level with the water in the pot. This allows the acetone to heat at a slow and steady rate. The fan is set up to blow the vapor straight out of an open window.

Part suspended under hoodPart suspended under hood

For the first experiment, the part was suspended under the metal shade of the lamp using fishing line tied around the base. This turned out to be totally unnecessary, and actually made it difficult to slowly and steadily lower the part into the acetone-filled jar. It was actually much easier to loop the string around the arm of the lamp, and lower it slowly and steadily into the jar.

Lowering the part into the boiling acetoneLowering the part into the boiling acetone

Once suspended inside the jar of boiling acetone, the part will turn shiny and smooth almost immediately. Ten seconds is more than enough to give the part a shiny, smooth finish. To speed up the process, a small piece of aluminum foil can be added as a lid to keep the vapor in the jar.

The part being treatedThe part being treated

If using an aluminum foil lid, ten seconds is more than enough time to fully treat the part.

JWE_0367This part has been left in too long; note the slightly melted appearance

If you leave the part in the bath for too long, it will  begin to melt and drip down into the acetone, creating an ABS slurry. The bright side is that this slurry can be used as a paste for welding together ABS parts, but try to avoid it if possible. Retract the part by pulling the string, and hang the part up to dry. A few minutes should be enough for the acetone to dissolve.

A treated partA treated part
Close up of a treated partClose up of a treated part
Comparison shot of a treated and untreated partComparison shot of a treated and untreated part
Treated model and untreated model Comparison shot of a treated and untreated part
JWE_0444Can you spot the untreated part? Virgie can!

Treating 3D-printed ABS parts with a acetone vapor bath is a great way to create a smooth finish. Proper care needs to be exercised when using boiling acetone vapor, as it is a dangerous chemical.

If you decide to do this yourself, take lots of pictures, and let me know what you find out!

Owl statue by cushwa – Thingiverse link
Photography assistant – John Ewing
Original idea –