3D Print Acetone Smoothing: ABS Vapor Bath Guide

Acetone vapour smoothing is a chemical finishing technique that transforms rough ABS 3D prints into smooth, glossy objects that look injection moulded. The process dissolves the outer surface of the ABS plastic, causing it to flow and fill in layer lines. When done correctly, the results are stunning.

How Acetone Vapour Smoothing Works

ABS (Acrylonitrile Butadiene Styrene) dissolves in acetone. In vapour form, acetone gently melts the outermost layer of an ABS print, causing the surface to become liquid and flow smooth before evaporating. The result is a glossy, seamless surface with no visible layer lines.

Important: This technique only works with ABS and ASA filaments. PLA, PETG, Nylon, and TPU do not dissolve in acetone and cannot be vapour smoothed this way.

Materials and Safety Equipment Needed

You will need:

• Acetone: Pure acetone (nail polish remover with additives will not work). Available at hardware stores in India for ₹100-200 per litre
• Glass container: A large glass jar or container with a lid. Must be big enough for your print with space around it
• Aluminium foil: To line the container (if using a plastic container) and to create a stand
• Paper towels: To soak with acetone for the cold method
• Nitrile gloves: Acetone dissolves latex gloves. Use nitrile
• Safety goggles: Acetone vapour irritates eyes
• Well-ventilated area: Acetone vapour is flammable and should not be inhaled. Work outdoors or near an open window

Cold Vapour Method Step by Step

The cold method is safer and more controlled:

1. Line the inside of your glass container with paper towels
2. Soak the paper towels with acetone until damp but not dripping
3. Place a small stand (crumpled aluminium foil works) at the bottom so your print does not touch the wet towels
4. Place your ABS print on the stand
5. Seal the container with its lid or cling wrap
6. Wait 30-60 minutes, checking every 15 minutes
7. Remove the print when the surface appears evenly glossy
8. Let the print dry in open air for 24 hours to fully cure

The cold method takes longer but gives you more control. Over-smoothing is unlikely with this approach.

Hot Vapour Bath Method

The hot method is faster but riskier:

1. Pour a small amount of acetone (50-100 ml) into a glass container
2. Place the container on a low-temperature hot plate (40-50°C maximum — acetone boils at 56°C)
3. Place your print on a raised platform inside the container
4. Cover loosely — do not seal completely (pressure can build up)
5. The warm acetone evaporates faster, filling the container with dense vapour
6. Check every 2-3 minutes. The process is much faster than the cold method
7. Remove when evenly smoothed and let cure for 24 hours

SAFETY WARNING: Acetone vapour is extremely flammable. Never use an open flame. Never heat above 50°C. Work in a well-ventilated space away from any ignition source. The hot method is inherently more dangerous — beginners should use the cold method.

Controlling the Smoothing Process

Getting a perfect finish requires controlling these variables:

• Exposure time: Too short = uneven smoothing. Too long = features melt and detail is lost. Start with shorter times and repeat if needed
• Temperature: Warmer environments speed up the process. In Indian summers (35°C+), the cold method works faster than usual
• Print orientation: Suspend or rotate the print during smoothing for even coverage. Bottom surfaces often smooth less because vapour rises
• Multiple sessions: Two short sessions with 24 hours between them give more control than one long session

Common Mistakes and How to Avoid Them

• Using impure acetone: Nail polish remover contains water and additives that leave a hazy, uneven finish. Always use pure laboratory or hardware-grade acetone
• Over-smoothing: Fine details like text, edges, and thin features can melt away. Remove the print before it reaches perfection — it continues smoothing for a few minutes after removal
• Uneven smoothing: Usually caused by the print sitting directly on a surface. Use a wire stand or suspend the print
• Print deformation: If the vapour concentration is too high or the temperature too warm, the print can sag under its own weight. Use lower temperatures and shorter times
• Not curing: Always let the print dry for at least 24 hours. The surface remains soft until the acetone fully evaporates

Frequently Asked Questions