Drying Filament Comprehensive Guide From Start to Finish
Moisture is the silent enemy of 3D printing: even small amounts absorbed by filament can ruin print quality, weaken parts, and waste hours of printing time. This guide walks you through every step of drying filament, from identifying moisture damage to proper post-drying storage, to keep your 3D prints consistent and high-quality.
Why Dry Filament?
Most 3D printing filaments are hygroscopic, meaning they absorb water vapor from the air over time. When moist filament is extruded, the high temperature of the hotend turns trapped water into steam, causing a range of print defects:
- Popping or hissing sounds during extrusion
- Bubbles or pitting on the filament surface or printed part
- Excessive stringing, oozing, or blobbing
- Poor layer adhesion, leading to weak, brittle parts
- Dimensional inaccuracies or warping
- Reduced surface finish quality, with rough or uneven textures
Even "dry" looking filament can hold enough moisture to cause issues, especially for high-performance materials like nylon, TPU, and PETG.
When to Dry Your Filament
You don’t need to dry every spool on a schedule, but watch for these clear signs your filament has absorbed too much moisture:
- Audible popping or sizzling when extruding filament
- Visible steam or bubbles coming from the hotend or extruded filament
- Sudden drop in print quality after weeks of storage
- Filament that feels tacky or leaves residue on your hands
As a rule of thumb, dry filament if it’s been stored in open air for more than 2 weeks, or if you live in a high-humidity climate (relative humidity above 50%).
Tools for Drying Filament
Several tools can dry filament effectively, ranging from budget DIY options to dedicated commercial dryers. Choose based on your budget, filament volume, and frequency of use:
Dedicated Filament Dryers
Commercial dryers (e.g., Sunlu S2, Creality Space Pi) are purpose-built for filament drying, with precise temperature control, air circulation, and spool compatibility for most standard sizes (1kg, 750g). Pros: consistent results, safe for all filament types, often double as dry storage. Cons: higher upfront cost than DIY options.
Food Dehydrators
Standard food dehydrators work well for filament drying, as they maintain low, consistent temperatures and circulate air. Pros: affordable, widely available, can dry multiple spools at once. Cons: may not fit larger spools, temperature accuracy varies by model.
Conventional Ovens
Home ovens can dry filament if they hold a steady low temperature (below 90°C). Pros: free if you already own one. Cons: high risk of overheating (melting filament or warping plastic spools), uneven temperature distribution, not recommended for frequent use.
DIY Options
Budget DIY setups include foam coolers with low-wattage ceramic heaters, or sealed bins with desiccant and warm air pumps. Pros: extremely low cost. Cons: require more monitoring, less consistent results, higher risk of fire if not built properly.
Supporting Tools
Pair your dryer with a digital hygrometer to monitor humidity levels, and moisture-resistant storage (vacuum seal bags, dry boxes with silica gel desiccant) to keep filament dry after processing.
Step-by-Step Filament Drying Process
Follow these steps for consistent, safe drying results:
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Check filament specifications: Look up the manufacturer’s recommended drying temperature and time for your specific filament type. Use the reference table below if unavailable:
Filament Type
Recommended Drying Temp (°C)
Typical Drying Time (Hours)
PLA
40-50
4-6
PETG
60-70
6-8
ABS/ASA
70-80
8-10
TPU (Flexible)
50-60
6-8
Nylon (PA)
80-90
12-24
PC (Polycarbonate)
80-90
10-12
Preheat your dryer: Set the dryer to the correct temperature and let it preheat for 10-15 minutes to ensure stable conditions.
Load the filament: Keep filament on its original spool (remove any plastic wrap) and place it in the dryer. Ensure air can circulate around the spool—do not stack multiple spools if your dryer is not rated for it.
Set the timer: Adjust drying time based on how moist the filament is (longer for spools stored in high humidity). Check the filament halfway through if drying for more than 8 hours.
Monitor progress: Listen for popping sounds when extruding a small test string—if popping stops, the filament is dry. Avoid opening the dryer frequently, as this lets in humid air.
Cool and store: Once drying is complete, let the filament cool inside the dryer or transfer it immediately to a vacuum-sealed bag or dry box with desiccant. Do not leave cooled filament in open air.
Post-Drying Storage Best Practices
Drying is only half the battle—proper storage prevents filament from reabsorbing moisture within days. Follow these rules:
- Use vacuum-seal bags with a packet of silica gel desiccant for long-term storage (up to 6 months for most filaments).
- For active use, store filament in a dry box with a sealed gasket, active dehumidifier, and hygrometer to monitor humidity (keep below 20% RH).
- Avoid storing filament in garages, basements, or other high-humidity areas.
- Label dried spools with the date of drying to track freshness.
Common Drying Mistakes to Avoid
- Overheating: Exceeding the recommended temperature can melt filament, warp plastic spools, or degrade the material’s mechanical properties.
- Underdrying: Cutting drying time short leaves residual moisture, leading to print defects. When in doubt, add 1-2 extra hours for high-humidity environments.
- Using the printer’s hotend to dry filament: This wastes energy, clogs nozzles, and does not dry the entire spool evenly.
- Skipping post-drying storage: Filament left in open air after drying will reabsorb moisture within 24-48 hours in moderate humidity.
- Drying wet filament on the printer: Always remove the spool from the printer to dry it—dryers are not designed to work with mounted spools, and printer components may be damaged by heat.
Conclusion
Drying filament is a simple, low-effort step that drastically improves 3D print reliability and quality. By following this guide, you’ll eliminate moisture-related defects, extend the life of your filament, and get consistent results from every spool. Make filament drying and proper storage a regular part of your 3D printing workflow, and you’ll save time, money, and frustration in the long run.
