If you’ve ever experienced stringy prints, brittle lines, or even bubbling noises during extrusion — chances are, humidity might be the hidden culprit. 3D printer filament may look tough, but it’s surprisingly vulnerable to moisture. And once it absorbs water, your print quality takes a serious hit.
In this article, we’ll explain exactly how humidity affects filament, how to prevent it, and what you can do to rescue wet spools. Plus, we’ll show you smart storage solutions that can extend the life of your materials and your printer.
Why Filament and Humidity Don’t Mix
Filaments like PLA, ABS, PETG, and especially Nylon are hygroscopic, meaning they absorb moisture from the air. The more humid your room, the faster this happens. And once the moisture gets in, it changes everything.
Wet filament can cause:
- Popping or sizzling sounds during printing (as water evaporates).
- Weakened layer adhesion, resulting in fragile parts.
- Stringing and oozing, especially on detailed prints.
- Surface imperfections, like bubbles or matte finishes.
If you’ve been blaming your slicer settings or nozzle temperature, the real issue might be sitting quietly on your spool rack — soaking in the atmosphere.
What Happens at Different Humidity Levels?
Even if you don’t live in a rainforest, your workspace could be humid enough to damage filament in just a few days. Here’s a quick breakdown:
- <20% RH (Relative Humidity): Ideal for filament storage.
- 30–40% RH: Slow moisture absorption begins.
- 50%+ RH: Moisture absorption increases rapidly.
- 70%+ RH: Filament can become saturated in just 1–2 days.
Humidity doesn’t just affect storage — it can even influence printing on the fly. A hot-end extruding damp filament is a recipe for bubbling and nozzle clogs.
Which Filaments Are Most Affected?
All filaments absorb moisture, but some are far more sensitive than others:
- Nylon: Highly hygroscopic — can absorb water in mere hours.
- PVA: Designed to dissolve in water, so even ambient moisture affects it.
- TPU/TPE: Flexible materials tend to absorb faster.
PLA, PETG, and ABS are more forgiving, but long-term exposure will still degrade their quality.
How to Spot Moisture-Damaged Filament
Moisture damage isn’t always obvious, especially to the untrained eye. Here’s how to identify it:
- Audible popping during extrusion.
- Rough or uneven surface texture on prints.
- Increased stringing between print segments.
- Brittle filament that breaks when unspooled.
Want to be sure? Try a quick print test with a known-good file. If the result looks off despite your usual settings, moisture might be to blame.
The Best Ways to Store Filament (Moisture-Free!)
Protecting your filament starts with smart storage. Even a few simple steps can make a massive difference in quality:
- Use airtight containers with desiccants (like silica gel).
- Invest in a filament dry box that maintains low humidity.
- Store opened spools in vacuum-sealed bags.
- Keep a humidity gauge inside storage areas to monitor RH levels.
Can You Save Wet Filament? Absolutely.
If you’ve got a spool that’s already absorbed moisture, don’t throw it away just yet. Most filaments can be rescued with controlled drying.
Here’s how:
- Use a filament dryer with temperature control.
- Dry PLA at ~45–50°C, PETG at 55–60°C, and Nylon at 70–80°C.
- Let it dry for 4–6 hours depending on how long it’s been exposed.
Never use a microwave (bad idea) and avoid open ovens without a thermometer — too much heat can permanently damage the filament.
Pro Tips to Stay Dry All Year Round
Want to go next level with filament care? Try these practices:
- Label each opened spool with a date.
- Refresh silica gel packs regularly.
- Don’t leave spools on the printer between sessions.
- Use humidity indicator cards to monitor storage bins.
These small habits can save you hundreds in wasted prints and keep your 3D projects running smoothly.
Final Thoughts: Moisture Is the Silent Print Killer
Humidity may be invisible, but its effects on 3D printing are loud and clear. Poor layer adhesion, stringing, and fragile prints often trace back to wet filament. But with a little knowledge and the right tools, you can eliminate moisture as a variable and unlock flawless prints — every time.