--- title: "What Is Vapor Smoothing? The Complete Guide | AMT PostPro" description: "Vapor smoothing seals and smooths 3D printed polymer parts with a controlled solvent vapor. How it works, what it does, materials, results and limits." canonical: https://amtechnologies.com/learn/what-is-vapor-smoothing/ updated: 2026-10-07 type: learn --- Learn · Explainer # What is vapor smoothing? Vapor smoothing (also spelled vapour smoothing) is a chemical finishing process for 3D printed polymer parts. A controlled solvent vapor softens the outer skin of the part, the surface reflows and seals, and the part comes out smooth inside and out. PostPro systems by AMT run it as one automated cycle: Conditioning · processing · curing · drying[1]. [Test your parts, free](https://benchmarking.amtechnologies.com/submit?utm_source=amtechnologies.com&utm_medium=learn-page&utm_campaign=site-2026&utm_content=learn-learn-hero) [See the systems](https://amtechnologies.com/products/vapor-smoothing/) No cost to evaluate · Parts returned · Typical turnaround 2–3 weeks[2] ![TPU bellows as printed, with a rough gray surface](https://amtechnologies.ai/img/ba-bellows-before-960.webp) As printed · ![The same TPU bellows after PostPro vapor smoothing, with a smooth, sealed surface](https://amtechnologies.ai/img/ba-bellows-after-960.webp) Vapor smoothed · Photo · The same 3D printed TPU bellows before and after PostPro vapor smoothing. Not retouched. - **Surface roughness**: 13.42 → 1.18 µm[3] - BASF Ultrasint TPU01 · HP MJF - **Dimensional change**: ≤ 0.4%[4] - PA12 · voxeljet HSS - **Burst pressure**: up to +7%[5] - PA2200 · SLS - **Cycle, SF50 and SF100**: 1.5–2 h[1] - Conditioning to drying 01 The process ## How vapor smoothing works Definition Vapor smoothing exposes a thermoplastic part to a controlled solvent vapor, so its outer surface softens, flows and resolidifies as a smooth, sealed skin, while the bulk of the part keeps its shape. A powder-bed 3D printed part, from HP Multi Jet Fusion or selective laser sintering for example, comes out of the printer with a grainy, porous surface made of partly fused powder. Vapor smoothing does not sand that surface away. It melts the very top of it for a moment so it levels itself, closes the pores and sets again. On a PostPro system that happens in four automated stages: 1. ### Conditioning Parts are conditioned in the chamber to reach the right processing conditions. 2. ### Processing Vaporized consumable is injected into the chamber and smooths part surfaces under controlled conditions. 3. ### Curing The consumable is removed from the surface and the surface resolidifies. 4. ### Drying Parts are dried so no consumable remains in the chamber, ready for use.[1] A full cycle takes 1.5–2 h (SF50, SF100) · 2 h (SFX, SF2X)[1]. Because the finishing agent reaches the part as a vapor, it acts on every exposed surface at once, including internal channels that no tool can reach. 02 The result ## What vapor smoothing does to a part Four things change, and AMT has published measurements for each. Every result below names the material it was measured on; results depend on material, printer and recipe. - Surface 13.42 → 1.18 µm[3] Surface roughness, as printed to vapor smoothed BASF Ultrasint TPU01 · HP MJF - Sealing Reduced surface porosity on UL94 V-0 flame-retardant parts[6] Case study HP 3D HR PA 12 FR · HP MJF - Strength +38.1% (XY)[4] Elongation at break PA12 · voxeljet HSS - Strength up to +7%[5] Burst pressure PA2200 · SLS - Dimensions ≤ 0.4%[4] Dimensional change PA12 · voxeljet HSS - Dimensions ≤ 0.4%[5] Dimensional change PA2200 · SLS ### Why sealing matters A sealed surface takes up less water, dirt and sweat, and is easier to clean. That is why vapor smoothing turns up on parts that are handled, worn or washed: prostheses, food-processing grippers and automotive seals.[7,8,9] The water test on the right shows the difference on two TPU bellows printed together: the drop beads on the vapor-smoothed part and soaks into the as-printed one. [TPU and elastomer results](https://amtechnologies.com/materials/tpu/) · [PA12 results](https://amtechnologies.com/materials/pa12/) FOOTAGE · Water test: a drop beads on the vapor-smoothed bellows (left) and soaks into the as-printed one (right). 03 Compatibility ## Which printing processes and materials PostPro vapor smoothing is built for powder-bed and industrial extrusion parts: MJF, SLS, SAF and HSS; FDM ULTEM and Onyx parts on SFX[1]. On those printers it finishes nylons, elastomers and polypropylene, plus a long list of other thermoplastics. - Nylon MJF · SLS · SAF · HSS ### [PA12](https://amtechnologies.com/materials/pa12/) - Nylon MJF · SLS · SAF · HSS ### [PA11](https://amtechnologies.com/materials/pa11/) - Elastomers MJF · SLS · SAF · HSS ### [TPU and TPE](https://amtechnologies.com/materials/tpu/) - Polyolefin MJF · SLS ### [Polypropylene](https://amtechnologies.com/materials/polypropylene/) - Machined CNC ### [Machined plastics](https://amtechnologies.com/applications/vapor-polishing-machined-plastics/) - Everything else ### [All materials](https://amtechnologies.com/materials/) The finishing agent decides the material list. PostPro Pure runs in every PostPro system; FA326 adds 100+ thermoplastics[10] on the SF50 and SF100; FA9202 is the dedicated agent for polypropylene.[10] By printing process: [MJF](https://amtechnologies.com/learn/mjf-vapor-smoothing/) · [SLS](https://amtechnologies.com/learn/sls-vapor-smoothing/) · [SAF and HSS](https://amtechnologies.com/learn/saf-hss-vapor-smoothing/) · [industrial FDM](https://amtechnologies.com/learn/fdm-vapor-smoothing/). 04 Equipment ## Manual vs automated, closed-loop smoothing Hobbyists smooth ABS prints with acetone vapor in a jar or a heated box. It works on some extrusion plastics, but the operator controls nothing precisely: time, temperature and vapor concentration drift, results vary from part to part, and the solvent vapor escapes into the room. Industrial vapor smoothing turns that into a controlled machine process. On a PostPro system: - **SF50 and SF100:** Closed-loop system with consumable recovery[1]; RFID consumable recognition and management[1]; RFID-controlled access[11]. - **SFX desktop system:** No external extraction system required[11]; Quick-change recovery cartridge[11]. - **SFX, SF50 and SF100:** the cycle runs from a recipe on the touchscreen, not from a stopwatch.[11] That is what makes vapor smoothing repeatable enough for production parts. [Compare the four PostPro systems](https://amtechnologies.com/products/vapor-smoothing/). 05 Alternatives ## Vapor smoothing vs other finishing methods Abrasive methods such as media finishing, tumbling and sanding remove or flatten material and leave the surface open. Dyeing changes color, not texture. Coatings add a layer that seals as long as it stays intact. Vapor smoothing reflows the part’s own surface, so it smooths and seals in one step, and it is often combined with dyeing. [Vapor smoothing vs sanding, tumbling, dyeing and coating, side by side](https://amtechnologies.com/learn/vapor-smoothing-vs-other-finishing-methods/) 06 Terms ## Vapor smoothing vs vapor polishing Same principle, different starting part. **Vapor polishing** is the machine-shop name for reflowing the surface of machined plastic parts, usually to bring back clarity on polycarbonate or acrylic. **Vapor smoothing** is the name used for 3D printed parts, where the process also seals a porous surface. AMT does both: machined plastics run on the PostPro SF100 with PostPro Pure[12]. [Vapor polishing for CNC-machined plastics](https://amtechnologies.com/applications/vapor-polishing-machined-plastics/) · [Not to be confused with vapor honing](https://amtechnologies.com/learn/glossary/#vapor-honing) 07 Origins ## Who made vapor smoothing industrial Smoothing plastics with solvents is older than 3D printing. Turning it into an automated, controlled process for industrial 3D printed parts is AMT’s work. Born from University of Sheffield research[13]: AMT was founded in Sheffield in 2017. - The first automated vapor smoothing system for powder-bed 3D printed parts[14]: the PostPro3D. - The largest patent portfolio in vapor smoothing[14]: 50+[15] patents in post-processing technology, among them EP3565712 · GB2582225 · GB2597240B[11]. - The world's largest installed base of automated vapor smoothing systems[14]: 900+[15] PostPro systems installed in 40[15] countries. [The patents](https://amtechnologies.com/patents/) · [The team behind them](https://amtechnologies.com/about/) 08 Next ## Getting started with vapor smoothing There are three ways in. 1. **Test your own parts.** Send parts to the free benchmark and get them back vapor smoothed with a report: No cost to evaluate · Parts returned · Typical turnaround 2–3 weeks.[2] 2. **Outsource.** The PostPro network has 125+[16] production partners in the PostPro network that sell vapor smoothing as a service. [Find a partner](https://amtechnologies.com/postpro-partners/). 3. **Bring it in-house.** Compare the systems, see the list prices and work out your cost per part: [systems](https://amtechnologies.com/products/vapor-smoothing/) · [prices](https://amtechnologies.com/pricing/) · [ROI calculator](https://amtechnologies.com/roi/). Questions ## Vapor smoothing, explained. Short answers from AMT’s published specifications and tests. Anything else, [ask an engineer](https://share.hsforms.com/1lOH82JpuRdSM-4wJ1ZeYlw45o6d?website_source=Vapor+Smoothing&utm_source=amtechnologies.com&utm_medium=learn-page&utm_campaign=site-2026&utm_content=learn-talk). ### What is vapor smoothing? Vapor smoothing finishes 3D printed polymer parts with a controlled solvent vapor. PostPro systems seal and smooth powder-bed 3D printed parts inside and out in one automated cycle with four stages: Conditioning · Processing · Curing · Drying[1]. ### Is vapor smoothing the same as vapor polishing? They work on the same principle: a controlled vapor reflows the surface of a thermoplastic part. Vapor polishing is the usual name for machined plastic parts, vapor smoothing for 3D printed parts, where it also seals the surface. ### Which 3D printing technologies does it work with? Powder-bed and industrial extrusion parts from MJF, SLS, SAF and HSS; FDM ULTEM and Onyx parts on SFX[1]. ### Which materials can be vapor smoothed? On the PostPro SF50 and SF100: PA12 · PA11 · TPU · TPE · PP with FA9202[1,10]. With the FA326 agent, the SF50 and SF100 cover 100+ thermoplastics[10]. ### Does vapor smoothing change part dimensions? Very little. AMT’s published tests measured a dimensional change of ≤ 0.4%[4] on HSS PA12 parts and ≤ 0.4%[5] on SLS PA2200 parts. ### How long does vapor smoothing take? A cycle takes 1.5–2 h[1] on the PostPro SF50 and SF100, and 2 h[1] on the SFX and SF2X. ### Can vapor-smoothed parts be used in contact with food? For one tested combination, yes: parts printed in FABULOUS DETECT PA11 · PostPro Pure were tested by an independent lab, with Extractables well within regulatory limits under US FDA 21 CFR §177.1500[17]. Other materials and agents need their own testing. ### Who invented vapor smoothing for 3D printing? Solvent smoothing of plastics is older than AMT; automated vapor smoothing for industrial 3D printing started at AMT. The first automated vapor smoothing system for powder-bed 3D printed parts[14]: AMT’s PostPro3D. The largest patent portfolio in vapor smoothing[14], with 50+[15] patents in post-processing technology. Next step ## See the price. Run the numbers. Hold the part. List prices are public and the cost-per-part math is yours to check, with no email needed for either. The free benchmark puts your own parts, vapor smoothed, in your hands. 1. 01 Quote ### Build your quote Pick a system and its options and get an itemized total on screen, from AMT’s published list prices. [Build your quote](https://amtechnologies.com/quote/) 2. 02 ROI ### Calculate your ROI Compare your cost per part with manual finishing, using your own labor rate and volumes. Every assumption is editable. [Calculate ROI](https://amtechnologies.com/roi/) 3. 03 Benchmark ### Test your parts, free Ship us your parts with a prepaid label. We vapor smooth them and send them back with before-and-after photos and a benchmark report. [Test your parts, free](https://benchmarking.amtechnologies.com/submit?utm_source=amtechnologies.com&utm_medium=learn-page&utm_campaign=site-2026&utm_content=learn-decision) No cost to evaluate · Parts returned · Typical turnaround 2–3 weeks[2] Prices: AMT list prices, excluding tax and shipping; confirmed in your formal quote. [Not sure which system? Help me choose](https://amtechnologies.com/configurator/) ## Sources 1. [Vapor smoothing: SF and X-series family page and SFX, SF2X, SF50, SF100 product pages](https://amtechnologies.com/products/vapor-smoothing/) · AMT · read Oct 6, 2026 · also [AMT](https://amtechnologies.com/products/vapor-smoothing/postpro-sfx-desktop-vapor-smoothing-system/) · also [AMT](https://amtechnologies.com/products/vapor-smoothing/postpro-sf2x/) · also [AMT](https://amtechnologies.com/products/vapor-smoothing/postpro-sf50/) · also [AMT](https://amtechnologies.com/products/vapor-smoothing/postpro-sf100/) 2. [PostPro benchmarking: send us your 3D printed parts](https://benchmarking.amtechnologies.com/) · AMT · read Oct 6, 2026 3. [Ultrasint TPU01 enhancement with PostPro vapor smoothing (whitepaper)](https://amtechnologies.com/resources/whitepapers/surface-enhancement-of-ultrasint-tpu01-parts-by-postpro-vapor-smoothing/) · AMT · Nov 7, 2022 4. [Vapor smoothing voxeljet's HSS PA12 with AMT PostPro (whitepaper)](https://amtechnologies.com/resources/whitepapers/vapor-smoothing-voxeljets-hss-pa12-with-amt-postpro/) · AMT · Feb 6, 2024 5. [Performance improvements of vapor smoothed SLS PA2200 parts (whitepaper)](https://amtechnologies.com/resources/whitepapers/performance-improvements-of-vapour-smoothed-sls-pa2200-parts/) · AMT · Jan 8, 2024 6. [Flame-retardant 3D-printed parts with UL94 V-0 compliance (Protolabs case study)](https://amtechnologies.com/resources/case-studies/flame-retardant-3d-printed-parts/) · AMT · Jun 3, 2026 7. [Designing 3D-printed partial hand prostheses patients want to wear (Point Designs case study)](https://amtechnologies.com/resources/case-studies/3d-printed-partial-hand-prostheses/) · AMT · Jul 2, 2026 8. [Marel salmon side gripper: creating sealed and sterilizable surfaces with AMT PostPro vapor smoothing (case study)](https://amtechnologies.com/resources/case-studies/marel-salmon-side-gripper-sealed-and-sterilizable-surfaces-vapor-smoothing/) · AMT · Jun 5, 2024 9. [GM's success: vapor smoothing for automotive production (spoiler closeout seal case study)](https://amtechnologies.com/resources/case-studies/basf-ultrasint-tpu01/) · AMT · Jan 23, 2023 · also [AMT](https://amtechnologies.com/industries/automotive/) · also [Forward AM](https://forward-am.com/gain-knowledge/blog/additive-manufacturing-gets-cars-into-showrooms/) 10. [Vapor smoothing consumables: PostPro Pure (FA5802), FA326 and FA9202](https://amtechnologies.com/products/vapor-smoothing/consumables/) · AMT · read Oct 6, 2026 11. [AMT PostPro brochure: automated post-processing systems for additive manufacturing, V4.0 (June 2026)](https://info.amtechnologies.com/download-document?document_name=brochure) · AMT · Jun 2026 12. [AMT company statement: SF100 + PostPro Pure vapor polishing of machined plastics (PC, PMMA, ABS, PSU, PEI, PA)](https://amtechnologies.com/applications/vapor-polishing-machined-plastics/) · AMT · Oct 6, 2026 13. [AMT company statement: born from University of Sheffield research; founded in Sheffield](https://amtechnologies.com/about/) · AMT · Oct 6, 2026 14. [AMT company statement: world's largest installed base of automated vapor smoothing systems; first automated vapor smoothing system for powder-bed parts (PostPro3D); largest patent portfolio in vapor smoothing](https://amtechnologies.com/about/) · AMT · Oct 6, 2026 15. [Raise3D announces partnership with AMT to bring advanced post-processing to RMS220 SLS 3D printer](https://amtechnologies.com/news/raise3d-and-amt-partnership/) · AMT · Apr 2, 2026 · also [3D ADEPT Media](https://3dadept.com/raise3d-and-amt-join-forces-to-deliver-end-to-end-sls-post-processing-in-europe/) 16. [PostPro partners: production partners and reseller network](https://amtechnologies.com/postpro-partners/) · AMT · read Oct 6, 2026 17. [Fabulous and AMT validate food contact compliance for 3D-printed parts using DETECT PA11 and PostPro Pure](https://amtechnologies.com/news/fabulous-and-amt-validate-3dprinted-food-contact-compliance/) · AMT · Apr 7, 2026