Best Vapor Smoothing Techniques for 3D Printing

Warning: The use of solvents like acetone, THF, and MEK for vapor smoothing can pose significant health risks if not handled properly. These chemicals are very toxic and flammable. Inhalation, skin contact, or ingestion can cause severe health problems, including respiratory issues, organ damage, and even death. Always follow safety guidelines, work in a well-ventilated area, and wear appropriate personal protective equipment (PPE). If you are unsure about the risks involved or do not have the necessary safety equipment, consider alternative smoothing methods or consult with a professional.

Vapor smoothing is a post-processing method that enhances the surface quality of 3D printed parts by exposing them to solvent vapors. This technique can create a glossy, smooth surface by melting the outer layer of the print material. While vapor smoothing is effective in improving aesthetics and occasionally enhancing strength, it comes with safety considerations due to the chemicals involved. This post dives into the most common vapor smoothing methods, safety measures, and proper disposal of used chemicals.

How Vapor Smoothing Works

Vapor smoothing works by exposing a 3D printed part to a solvent that selectively melts the surface layer. The molten layer self-levels, filling in layer lines and surface imperfections. Once the solvent evaporates, the plastic hardens again, leaving a polished finish. This process is particularly effective for prints made with thermoplastics that are reactive to specific solvents.

Common Vapor Smoothing Techniques

1. Acetone Vapor Smoothing (for ABS and ASA)
   Acetone vapor smoothing is one of the most popular techniques for ABS and ASA filaments. Acetone vapor melts the outer layer of the plastic, giving it a smooth and shiny appearance.
   Process:
   • Place the printed object in a sealed container with a small amount of acetone.
   • Heat the container gently or allow it to sit at room temperature until the vapors condense on the print.
   • Allow the print to dry once the desired smoothing effect is achieved.
2. Safety Measures:
   • Acetone is highly flammable. Keep it away from open flames or heat sources.
   • Work in a well-ventilated area or, ideally, a fume hood to avoid inhaling fumes.
   • Wear nitrile gloves and eye protection to prevent skin and eye contact.
   • Use a respirator if you're in a confined area without proper ventilation.
3. Tetrahydrofuran (THF) Vapor Smoothing (for PLA)
   PLA is not highly reactive to acetone but can be smoothed using Tetrahydrofuran (THF). THF dissolves PLA similarly to how acetone works with ABS.
   Process:
   • Use a sealed container with a small amount of THF.
   • Heat the container slightly to create vapors that coat the print's surface.
   • Remove the part after smoothing and allow it to dry thoroughly in a well-ventilated area.
4. Safety Measures:
   • THF is flammable and highly toxic if inhaled or absorbed through the skin.
   • Work in a well-ventilated area or fume hood, wearing a respirator.
   • Wear chemical-resistant gloves and goggles.
   • Store away from heat and flame sources.
5. MEK (Methyl Ethyl Ketone) Vapor Smoothing (for PETG)
   Methyl Ethyl Ketone (MEK) can be used for smoothing PETG prints. It acts similarly to acetone but is better suited for PETG, which resists acetone vapor.
   Process:
   • Place a small amount of MEK in a container with the print.
   • Allow the vapor to interact with the surface for a short time.
   • Remove the part once the desired effect is achieved and let it cure in fresh air.
6. Safety Measures:
   • MEK is highly flammable and can cause irritation or damage to the respiratory system.
   • Always work in a fume hood or highly ventilated area.
   • Wear a respirator and protective gloves when handling MEK.
   • Store MEK in an explosion-proof container away from direct sunlight or heat.

List of Chemical Toxicity for Vapor Smoothing

Note: These chemicals should be treated with caution. Ensure proper ventilation, protective equipment, and storage when using them.

Chemical Effectiveness Chart

Safely Getting Rid of Spent Chemicals

Used solvents should never be poured down the drain or disposed of in regular trash bins. Follow these guidelines for safe disposal:

• Collection in Sealed Containers
  • After use, collect the leftover chemicals in a tightly sealed, solvent-resistant container. Ensure that the container is properly labeled with the chemical name and date.
• Proper Disposal through a Waste Facility
  • Do not throw these chemicals into the regular trash. Instead, locate a nearby hazardous waste disposal facility or collection point, which will safely handle chemical disposal.
• Neutralizing Small Quantities
  • For tiny amounts, some chemicals can be neutralized under specific conditions, but it’s generally safer to rely on professionals for disposal. Follow local laws regarding chemical waste.

In-Depth Process for Vapor Smoothing 3D Prints with Each Chemical

Each vapor smoothing method requires a specific chemical suited to the type of filament used. The following sections detail the step-by-step process for using acetone, Tetrahydrofuran (THF), and Methyl Ethyl Ketone (MEK) for vapor smoothing, along with essential safety measures and considerations to ensure successful results.

Acetone Vapor Smoothing for ABS and ASA

Overview: Acetone is the most popular chemical for vapor smoothing ABS and ASA 3D prints. Acetone vapors dissolve the surface layer of the print, creating a glossy, smooth finish. The process is relatively easy but requires safety precautions due to acetone’s high flammability and fumes.

Step-by-Step Process

1. Preparation of Materials
   • Ensure you are working in a well-ventilated area or under a fume hood.
   • Gather a sealable container (preferably glass or stainless steel) that can fit your 3D print.
   • Have gloves, eye protection, and a respirator on hand to avoid direct contact with acetone and inhalation of fumes.
   • Set aside a small, non-reactive plate or stand to elevate the print above the liquid acetone.
2. Pour Acetone into the Container
   • Pour a small amount of acetone (about 10-15 mL) into the bottom of the container.
   • Avoid direct contact between the print and the acetone liquid. Instead, allow the vapors to rise and interact with the part.
3. Place the 3D Print in the Container
   • Place your 3D print on the stand inside the container.
   • Seal the container to trap the acetone vapors.
4. Monitor Vapor Smoothing
   • Let the acetone vapors work on the print for 10-30 minutes. The exact time depends on the size of the part and the desired smoothness.
   • Check the part every few minutes to ensure that the surface isn’t melting too much. The surface should smooth out without deforming the geometry.
5. Drying and Curing
   • Once the desired smoothness is achieved, remove the print carefully (using gloves) and place it in a well-ventilated area to air dry.
   • Allow at least 12-24 hours for the acetone to fully evaporate and the part to cure.

THF Vapor Smoothing for PLA

Overview: PLA is resistant to acetone, making Tetrahydrofuran (THF) a better choice for vapor smoothing. THF is a highly volatile and toxic solvent that melts the outer layer of PLA prints, resulting in a smoother surface. Extreme caution is required when handling this chemical due to its high toxicity and flammability.

Step-by-Step Process

1. Preparation of Materials
   • Work in a fume hood or a well-ventilated outdoor space since THF fumes are toxic.
   • Have a glass or stainless steel container with a secure, airtight lid ready.
   • Wear nitrile gloves, safety goggles, and a respirator designed for organic solvent vapors.
   • Place your PLA print on a stand to avoid direct contact with liquid THF.
2. Pour THF into the Container
   • Carefully pour a small amount of THF (about 10 mL) into the bottom of the container.
   • Ensure that the liquid stays far from the print, as direct contact can cause over-melting.
3. Place the PLA Print in the Container
   • Position the print in the container and seal the lid tightly to contain the vapors.
   • THF vapor smoothing typically works faster than acetone, so keep a close eye on the print.
4. Monitor Vapor Smoothing
   • Let the vapors condense on the print for 5-15 minutes, depending on the size and thickness of the part.
   • Check the print every few minutes to prevent excessive melting or deformation.
5. Drying and Curing
   • Once you achieve the desired smoothness, remove the print with gloves and allow it to air dry in a well-ventilated area.
   • Allow the part to cure for 24 hours to ensure all THF residues evaporate, leaving a solid, smooth surface.

MEK Vapor Smoothing for PETG

Overview: Methyl Ethyl Ketone (MEK) is an effective solvent for smoothing PETG prints. Although PETG resists acetone, MEK works similarly but with added caution due to its potential health hazards and higher toxicity.

Step-by-Step Process

1. Preparation of Materials
   • Ensure that you’re in a highly ventilated space or fume hood. MEK is both toxic and flammable.
   • Use chemical-resistant gloves, safety goggles, and a respirator.
   • Prepare a glass container with a lid and a non-reactive stand to elevate your PETG print.
2. Pour MEK into the Container
   • Pour a small amount of MEK (around 10 mL) into the container. Ensure the liquid does not directly contact the print.
   • Close the container to trap the vapors.
3. Place the PETG Print in the Container
   • Place the PETG print on the stand and seal the container tightly.
   • The MEK vapor will begin interacting with the surface of the print, causing it to melt and smooth out.
4. Monitor Vapor Smoothing
   • Vapor smoothing with MEK takes around 10-20 minutes. The time depends on the size and complexity of the part.
   • Open the container and check the print periodically to avoid over-smoothing or warping.
5. Drying and Curing
   • Carefully remove the part using gloves and place it in a well-ventilated space to dry.
   • Allow the print to cure for 24 hours to ensure that all MEK evaporates and the print is safe to handle.

Brush and Spray Smoothing

Brush Smoothing:

• Process:Dip a soft-bristled brush into the chosen solvent (acetone, THF, or MEK). Gently apply the solvent to the surface of the 3D print, focusing on areas that require smoothing. Allow the solvent to evaporate, then repeat as needed.
• Advantages:Offers more precise control over the smoothing process, particularly for small or intricate details.
• Disadvantages:Can be time-consuming and requires careful application to avoid unevenness.

Spray Smoothing:

• Process:Use a specialized spray gun or aerosol can to apply a fine mist of solvent onto the 3D print. Allow the solvent to evaporate, then repeat as needed.
• Advantages:Efficient for smoothing larger surfaces and can provide a more even finish.
• Disadvantages:Requires careful control to avoid over-smoothing or solvent runoff.

General Safety Measures for Vapor Smoothing

• Work in a Well-Ventilated Area: Always work in a fume hood or outdoors when using solvents like acetone, THF, or MEK.
• Wear Protective Gear: Nitrile gloves, safety goggles, and a respirator rated for organic vapors are essential for protecting yourself from the harmful effects of solvent exposure.
• Avoid Heat and Flames: All three chemicals (acetone, THF, and MEK) are highly flammable. Keep them away from open flames, sparks, and heat sources.
• Store Chemicals Properly: Store solvents in tightly sealed, labeled containers in cool, dry areas away from direct sunlight or ignition sources.

Safely Disposing of Used Chemicals

1. Collect Spent Chemicals in a Sealed Container
   • After using a solvent, transfer any leftover liquid into a properly labeled, sealed container. Ensure that the container is made of a material resistant to the chemical and is leak-proof.
2. Transport to a Hazardous Waste Disposal Facility
   • Do not dispose of chemicals like acetone, THF, or MEK down the drain or in regular garbage bins. Take spent chemicals to a local hazardous waste disposal facility or recycling center that handles chemical waste.
3. Follow Local Laws
   • Always check your local regulations for disposing of hazardous materials. Some areas have specific protocols or designated collection points for chemical waste.

Alternative Smoothing Methods for 3D Prints

When vapor smoothing with chemicals like Acetone, THF, and MEK is not ideal, there are other methods to achieve a polished finish on your 3D prints. Some alternative approaches include:

• Sanding and Polishing: Manual sanding using fine-grit sandpaper can smooth layer lines on prints made from materials like PLA and ABS. Following this with polishing compounds gives a glossy finish. It’s labor-intensive but offers detailed control.
• Filler Primer: Applying a spray filler primer helps to fill in surface imperfections. After drying, it can be sanded down for a smooth, paint-ready finish. Ideal for post-processing decorative models.
• Epoxy Coating: Brushing or spraying epoxy resin onto the surface fills in gaps between layers, producing a durable, smooth finish. This method is especially popular for large models or items requiring a strong, water-resistant finish.
• Heat Gun Smoothing: Gently heating the surface of PLA prints with a heat gun can soften the plastic enough to blend the layer lines. However, excessive heat can deform the model, so careful control is required.
• Chemical Bath (Isopropyl Alcohol): For some resins, particularly in SLA printing, an isopropyl alcohol (IPA) bath can be used to clean and slightly smooth the print surface.

Troubleshooting Vapor Smoothing with Acetone, THF, and MEK

When using vapor smoothing chemicals, problems can arise that affect the final quality of your print. Here’s how to troubleshoot common issues:

• Blotchiness or Uneven Finish:
  • Cause: Inconsistent vapor exposure or improper distribution.
  • Solution: Ensure the vapor is evenly distributed in the smoothing chamber. For consistent results, use a sealed chamber with controlled vapor flow.
• Deformation:
  • Cause: Excessive exposure to vapors or high temperatures during the smoothing process.
  • Solution: Reduce the exposure time or distance between the print and the vapor source. Using a fan to evenly circulate the vapor can help mitigate hot spots.
• Loss of Detail:
  • Cause: Over-smoothing caused by too much time in the vapor.
  • Solution: Carefully monitor exposure time. Different materials and solvents require different times—Acetone for ABS typically takes just a few minutes, while THF and MEK may need more precise timing to avoid oversmoothing.
• Chemical Residue:
  • Cause: Condensation of vapor on the surface, especially with chemicals like MEK and THF.
  • Solution: Dry the print thoroughly before smoothing, and use minimal solvent amounts to avoid condensation.

Environmental Impact of Acetone, THF, and MEK

Each chemical used in vapor smoothing has unique environmental and health impacts, which should be considered before selecting a method:

• Acetone:
  • Impact: Acetone is relatively less harmful compared to THF and MEK. However, it is still a volatile organic compound (VOC) that contributes to air pollution. It’s flammable and can cause skin and eye irritation.
  • Disposal: Ensure proper ventilation when using Acetone, and dispose of any excess through local hazardous waste programs.
• THF (Tetrahydrofuran):
  • Impact: THF is a more aggressive solvent and is classified as a hazardous air pollutant. It is harmful to both human health and the environment, with significant risks of inhalation toxicity and groundwater contamination.
  • Disposal: THF requires careful handling and should not be poured down drains. Dispose of it following your region’s hazardous waste disposal protocols.
• MEK (Methyl Ethyl Ketone):
  • Impact: MEK poses similar environmental and health risks to Acetone but is considered more toxic and persistent in the environment. Inhalation or skin contact can lead to health issues.
  • Disposal: Proper ventilation, protective equipment, and responsible disposal of MEK are crucial. Never discard it with regular waste.

Safety Equipment for Vapor Smoothing Techniques

When using chemicals like Acetone, THF, and MEK for vapor smoothing, safety precautions are crucial to protect against harmful fumes, chemical burns, and fire hazards. Here’s a breakdown of the essential safety equipment:

Respiratory Protection:

Why it's needed: Vapor fumes from these chemicals are hazardous to inhale. They can cause respiratory irritation, dizziness, and even long-term health effects.

Recommended Respirators:

1. 3M 6200 Half Facepiece Reusable Respirator with 3M 60921 P100 Organic Vapor Cartridge: Offers strong protection against organic vapors like Acetone, THF, and MEK.

2. GVS Elipse P100 Half Mask Respirator: Another excellent option that provides protection from organic vapors and is comfortable for prolonged use.

3. Miller Electric Half Mask Respirator LPR-100: Provides a low-profile design and excellent filtration for organic vapors.

Ventilation:

Why it’s needed: Ensuring proper airflow helps to prevent the buildup of dangerous fumes. A fume hood or a well-ventilated workspace with exhaust fans is recommended to minimize chemical exposure.

Recommended Ventilation Setup:

Fume Extractor or Exhaust Fan: These devices help remove chemical vapors from the air. Use them in combination with respirators for best results.

Eye Protection:

Why it’s needed: Vapors from Acetone, THF, and MEK can irritate or damage the eyes, especially in enclosed spaces.

Recommended Eye Protection:

3M Virtua CCS Protective Eyewear: Provides a comfortable fit and anti-fog lenses that protect against vapor exposure.

Uvex Ultra-Spec 2000 Safety Glasses: Lightweight, impact-resistant, and designed to block chemical splashes and vapors.

Hand Protection:

Why it’s needed: Direct contact with chemicals like Acetone, THF, and MEK can cause skin irritation or chemical burns.

Recommended Gloves:

Ansell Solvex Nitrile Gloves: These chemical-resistant gloves are ideal for handling solvents like Acetone, MEK, and THF.

SHOWA 730 Nitrile Chemical-Resistant Gloves: Designed for chemical handling, these gloves offer a high level of resistance to solvents and protect the skin from harmful exposure.

Protective Clothing:

Why it’s needed: Chemical spills or vapors can harm exposed skin. Wearing proper protective clothing minimizes risks.

Recommended Protective Clothing:

Tyvek Coveralls: These lightweight coveralls provide full-body protection against chemical splashes and vapors.

Chemical-Resistant Apron: Provides an additional layer of protection when dealing with chemical solvents.

Fire Safety Equipment:

Why it’s needed: Acetone, THF, and MEK are all highly flammable chemicals. It’s important to minimize fire risks, especially when working with heat sources.

Recommended Fire Safety Setup:

Fire Extinguisher: Ensure you have a Class B fire extinguisher, which is designed for flammable liquids, nearby at all times.

Fire Blanket: Keep a fire blanket on hand in case of emergency to smother small fires quickly.

Safe Storage and Handling of Chemicals

• Storage:Store solvents in tightly sealed, labeled containers in a cool, dry place away from heat sources, direct sunlight, and ignition sources. Avoid storing solvents near flammable materials or oxidizers.
• Handling:Always wear appropriate personal protective equipment (PPE), including gloves, eye protection, and a respirator when handling solvents. Work in a well-ventilated area or under a fume hood.
• Spills:In case of a spill, immediately clean up the spill using absorbent materials. Avoid creating a larger mess by sweeping or spreading the spill. Dispose of contaminated materials properly according to local regulations.
• Disposal:Never pour solvents down the drain or into the trash. Dispose of them properly through a hazardous waste disposal facility. Follow local regulations for chemical waste disposal.

FAQ

How to Vapor Smooth 3D Prints?

• Place the print in a sealed container with the solvent of choice (acetone for ABS, THF for PLA, MEK for PETG). Allow the vapor to condense on the surface, then remove the part and let it dry.

Does Vapor Smoothing Make Parts Stronger?

• Vapor smoothing improves surface finish and sometimes increases layer adhesion, but it can weaken fine details and reduce dimensional accuracy. Use it cautiously for functional parts.

What is the Smoothest 3D Printing Method?

• Vapor smoothing is one of the best techniques for achieving a smooth finish with filaments like ABS and ASA. SLA printing, while not requiring smoothing, inherently produces smoother prints.

What Filaments Can Be Vapor Smoothed?

• ABS, ASA, and HIPS can be smoothed with acetone. PLA can be smoothed with THF, while PETG can be smoothed with MEK. Other filaments generally resist vapor smoothing techniques.