The Chemistry of Vapor Polishing
Acetone is an aggressive solvent for polymers containing styrene, including ABS and ASA. When exposed to acetone vapor, the outer microscopic ridges of the layer lines dissolve into a liquid slurry. Surface tension flattens the slurry into a glassy, continuous skin before evaporating.
The result is a lustrous, high-gloss part that completely hides FDM layer lines, improves water-tightness, and increases tensile layer bonding by up to 15%.
Cold Vapor Chamber vs Heated Vapor
- Cold Vapor Method (Safest): A sealed container lined with paper towels saturated in acetone. Parts are elevated on non-reactive wire mesh. Smoothing takes 30-90 minutes at ambient temperature. Slow and easily controlled.
- Heated Vapor Method (Industrial): Acetone is heated to its boiling point (56 °C) inside an explosion-proof reflux chamber. Smoothing completes in 10-30 seconds. Requires specialized industrial equipment and active exhaust ventilation.
Protecting Critical Dimensions
Acetone does not distinguish between decorative perimeters and tight bearing pockets. Sharp corners will radius (typically losing 0.2-0.4 mm of sharpness), and fine screw threads can soften. Mask critical bores with silicone plugs or size them undersized in CAD to ream out with a drill bit after smoothing is complete.
