Filament storage is one of those things beginners ignore until a perfectly good spool starts printing like garbage. Moisture is the enemy — and it ruins filament faster than most people expect.
Here's how to store filament correctly, how to tell when it's gone bad, and how to rescue wet filament.
Most 3D printing filaments are hygroscopic — they absorb moisture from the air. When wet filament is heated in your hotend, the moisture turns to steam, causing:
PLA can go bad in as little as a few days in a humid environment. PETG, Nylon, and TPU are even more sensitive.
The minimum you need:
Silica gel desiccant packs are cheap and reusable — bake them at 120°C for a few hours to regenerate when they're saturated. Most change colour when full (orange to green, or blue to pink depending on the type).
Purpose-built filament dry boxes are a step up:
Vacuum storage bags remove air entirely. Excellent for long-term storage of spools you won't use for months.
| Filament | Moisture Sensitivity | Storage Priority |
|---|---|---|
| Nylon (PA) | Extreme | Airtight + desiccant always |
| TPU / TPE | Very High | Airtight + desiccant always |
| PETG | High | Airtight storage recommended |
| ABS / ASA | Medium | Airtight storage recommended |
| PLA | Low-Medium | Airtight for long-term storage |
| PLA+ | Low-Medium | Airtight for long-term storage |
Nylon is the worst — it can absorb enough moisture to cause problems within hours of being left out in humid conditions.
Signs of moisture-damaged filament:
When in doubt, listen. A dry spool should extrude almost silently. Crackling = moisture.
A food dehydrator set to 45-50°C for PLA (65°C for PETG, 70-80°C for ABS/Nylon) works excellently. Most spools fit easily.
Drying times:
| Filament | Temperature | Time |
|---|---|---|
| PLA | 45°C | 4-6 hours |
| PETG | 65°C | 4-6 hours |
| ABS | 65°C | 4-6 hours |
| Nylon | 70-80°C | 8-12 hours |
| TPU | 45°C | 4-6 hours |
A filament dryer box like the Sunlu S2 or eSUN eBOX does the same job as a food dehydrator but is designed specifically for filament — you can even print directly from some models while drying.
A standard oven works but is risky — most ovens are inaccurate and can warp or melt spools if they spike too high. If you use an oven, use an oven thermometer and keep temperatures conservative. Not recommended for PLA.
Label your desiccant. Note the date you last regenerated it. Replace or regenerate every 3-6 months depending on your climate.
Store in a cool, dry place. Avoid garages or sheds with temperature swings — condensation forms when temperatures change rapidly.
Don't leave spools on the printer. If you're not printing for more than a day, put the filament back in storage. This is the most common mistake beginners make.
Buy a hygrometer. A cheap digital hygrometer (~£5) inside your storage box tells you the humidity level. Aim for below 15% RH.
Colour-changing desiccant is worth the small premium. You can see at a glance whether it needs regenerating without guessing.
Store filament in airtight containers with desiccant. For materials like Nylon and TPU, this is non-negotiable. For PLA, it's good practice for anything you won't use within a week or two.
If your prints start sounding like popcorn, dry your filament before diagnosing anything else — it fixes a surprising number of seemingly mysterious print quality issues.