In the world of 3D printing, achieving high-quality prints requires more than just precise settings and a well-maintained printer. One of the most underestimated threats to print quality is moisture. Over time, filament exposed to ambient air absorbs water molecules, compromising its structural integrity and leading to inconsistent or failed prints.
This in-depth guide will explain how moisture affects different filament types, how to recognize moisture-related problems, and how to properly store and restore filament to maintain optimal printing performance.
How Moisture Interacts With Filament
Many thermoplastics used in 3D printing are hygroscopic, meaning they absorb moisture from the environment. This moisture permeates the filament, even when it is seemingly dry to the touch. The impact becomes visible when the filament is heated in the printer’s hot end.
What Happens Inside the Nozzle?
When wet filament is extruded, the absorbed moisture quickly turns into steam due to the high temperatures of the hot end. This rapid phase change causes a variety of printing issues, including:
- Small internal steam explosions that create bubbles
- Sudden pressure spikes in the nozzle
- Inconsistent extrusion flow
The resulting print is often flawed both aesthetically and structurally.
Signs That Your Filament Has Absorbed Moisture
Before and during printing, several key symptoms can alert you to filament moisture contamination:
1. Popping and Hissing Noises
As moisture vaporizes during extrusion, it creates audible popping or hissing sounds. These noises are a clear indication of water content in the filament.
2. Stringing and Oozing
Excess moisture can cause inconsistent retraction, leading to unwanted stringing between print paths. This results in web-like fibers appearing on the print.
3. Surface Imperfections
Moisture leads to visible defects such as bubbles, pockmarks, or foamy textures on the surface of printed parts. These imperfections reduce the visual and functional quality of the print.
4. Poor Layer Adhesion
Steam pockets prevent layers from bonding properly, reducing structural strength. Parts printed with wet filament may delaminate or snap under pressure.
5. Brittle Filament Behavior
Moisture-damaged filament often becomes brittle, breaking easily when bent. This is especially true for PLA and Nylon.
Which Filaments Are Most Affected?
Different materials have varying sensitivities to moisture. Knowing how your filament behaves is crucial to prevention and storage.
Highly Hygroscopic Filaments
- Nylon: Absorbs moisture within hours. Severely degrades print quality.
- PVA: Water-soluble. Quickly becomes soft or mushy in high humidity.
- TPU/TPE: Flexible materials that swell and string when exposed to moisture.
- PETG: Can absorb moderate amounts of water. Results in oozing and foggy finishes.
Moderately Hygroscopic Filaments
- PLA: Holds up better than Nylon but still degrades after a few days of exposure.
- Polycarbonate: Tolerates low humidity for a while, but becomes brittle over time.
Low Hygroscopic Filaments
- ABS: Absorbs moisture more slowly but still benefits from dry storage.
- HIPS: Resistant to some extent, yet proper storage is still recommended.
No filament is entirely moisture-proof. All spools, regardless of type, should be stored properly to maintain consistent performance.
How to Prevent Moisture Damage
Proper handling and storage of filament are critical to preventing moisture-related issues. Here are the best practices:
Use Airtight Storage
Store filament in sealed containers with a gasket-lined lid. Plastic storage boxes, vacuum bags, and specialized filament dry boxes are commonly used.
Include Desiccants
Place silica gel packets or reusable desiccant canisters in your storage container. These absorb any remaining humidity and help keep your filament dry.
Use Vacuum Bags
Vacuum-sealed storage bags remove air and minimize moisture exposure. These are especially useful for long-term storage or sensitive materials like Nylon.
Monitor Humidity Levels
Keep your storage area under 20% relative humidity. Consider using a digital hygrometer to track moisture levels in your filament storage area.
How to Dry Wet Filament
If your filament has already absorbed moisture, don’t discard it. Most filaments can be restored using controlled drying techniques.
1. Use a Filament Dryer
Commercial filament dryers such as the Sunlu FilaDryer or PrintDry Pro maintain constant temperatures and are designed for safe, even drying.
- Set temperature according to the filament type
- Typical drying time ranges from 4 to 12 hours
2. Use a Food Dehydrator
A food dehydrator with temperature control can be repurposed for filament drying. Make sure the trays fit your spools and avoid overheating.
3. Use a Conventional Oven (With Caution)
If you don’t have a filament dryer, a kitchen oven may work. However, precise temperature control is critical to avoid deforming the filament.
- Preheat the oven to a safe drying temperature (e.g., 45–55°C for PLA)
- Dry for 4 to 6 hours
- Place the filament on a baking tray lined with foil
- Do not exceed the filament’s glass transition temperature
Never leave the oven unattended during drying.
Safe Drying Temperatures for Common Filaments
| Filament Type | Drying Temp (°C) | Time (Hours) |
|---|---|---|
| PLA | 40–45 | 4–6 |
| ABS | 65–70 | 4–6 |
| PETG | 60–65 | 4–6 |
| TPU | 40–50 | 6–8 |
| Nylon | 70–80 | 8–12 |
| PC | 70–80 | 6–8 |
| PVA | 45–50 | 4–6 |
Always refer to manufacturer recommendations for best results.
Long-Term Filament Care and Storage Tips
Preserving the quality of your filament goes beyond drying. A few habits can make a big difference:
- Keep unused spools sealed with desiccants
- Label each container with filament type and open date
- Never leave filament exposed for more than a few hours
- Regularly inspect your stored spools for signs of moisture
Investing in proper storage early will save time, money, and frustration in the long run.
Common FAQs About Moisture in Filament
Can I print with wet filament?
Yes, but it’s not advisable. Wet filament produces poor quality prints with weak mechanical properties and visible defects.
How long does it take for filament to absorb moisture?
It varies. Some materials like Nylon begin absorbing water within a few hours. PLA may take a few days in humid conditions.
Is moisture damage permanent?
Not always. Most filament can be dried and restored unless it has become too brittle or chemically degraded.
Can moisture cause nozzle clogs?
Yes. Steam from wet filament can create pressure spikes and leave residue, increasing the risk of jams.
Do I need a filament dryer for every material?
It depends on your climate and usage. If you live in a humid area or use materials like Nylon or TPU frequently, a dedicated dryer is highly recommended.
Conclusion
Moisture is one of the most silent but destructive enemies in 3D printing. Even minor water absorption can dramatically reduce print quality, mechanical strength, and part accuracy. Thankfully, with a proactive approach—drying, airtight storage, desiccants, and monitoring—you can preserve filament quality and avoid costly print failures.
Taking care of your filament is as important as calibrating your printer or slicing your model. By understanding and preventing moisture-related problems, you’re one step closer to consistently high-quality prints.