How Humidity Affects 3D Printing Filaments (And How to Prevent Issues)

If you've ever heard your 3D print hissing and popping like bacon on a griddle, you've experienced the effects of moisture-damaged filament. That water trapped in your material is boiling off during extrusion, creating steam bubbles that ruin surface finish, weaken layer adhesion, and turn what should be a clean print into a rough, stringy mess.

Here in Jacksonville, humidity isn't a seasonal concern—it's a daily reality. But even in drier climates, filament moisture management separates good prints from great ones. Understanding how water affects your material and how to prevent problems will make a noticeable difference in your results.

Why Filament Absorbs Water

Most 3D printing filaments are hygroscopic, meaning they actively pull moisture from the surrounding air. This isn't a surface-level issue—water molecules actually penetrate into the plastic itself, bonding with the polymer chains at a molecular level.

Different materials absorb water at different rates and to different extents:

Nylon (PA) is the worst offender, absorbing up to 7% of its weight in water. Leave a nylon spool exposed for a few hours in humid conditions, and you'll notice the difference.

PVA and PETG absorb moisture more slowly than nylon but are still significantly affected. PETG in particular can seem fine for weeks before gradually degrading.

PLA is relatively resistant to moisture—one of its many advantages—but will still absorb enough water over time to cause problems. Don't assume PLA is immune just because it's more forgiving.

TPU falls somewhere in the middle. Its flexibility can mask some moisture symptoms, but wet TPU produces weaker parts with poor layer bonding.

The rate of absorption depends on both the material and your environment. At 50% relative humidity, PLA might take weeks to absorb problematic amounts of moisture. At 80% humidity? Days—sometimes hours for sensitive materials like nylon.

What Happens When You Print Wet Filament

When moisture-laden filament hits your hotend's 200-280°C temperatures, that absorbed water instantly becomes steam. This creates several problems:

Bubbles and voids. Steam trapped in the extruded plastic creates pockets of gas. These show up as rough, pockmarked surfaces and small holes throughout your print. They also create weak points that can lead to part failure under stress.

Poor layer adhesion. The steam disrupts the bonding between layers as plastic is deposited. Water molecules interfere with polymer chain entanglement, producing layers that don't stick together properly. Parts printed with wet filament often delaminate under loads that dry-printed parts handle easily.

Stringing and oozing. Moisture changes how the molten plastic flows. Wet filament often strings excessively between travel moves and oozes from the nozzle during pauses, even with retraction settings that work perfectly for dry material.

Dimensional inaccuracy. Steam expansion during extrusion creates unpredictable variations in the amount of plastic being deposited. Your 20mm calibration cube might come out at 19.5mm or 20.3mm with wet filament.

Degraded mechanical properties. Studies have shown that PLA printed after high-humidity storage can lose 5-10% of its flexural strength and impact resistance. For functional parts, this matters.

How to Tell If Your Filament Is Wet

Recognizing wet filament early saves time and material. Here's what to look for:

During Printing

Audible clues are the most obvious. Popping, hissing, or sizzling sounds during extrusion mean water is boiling off. The more pronounced the sound, the wetter your filament. A single occasional pop might be acceptable; constant crackling means stop and dry.

Watch for steam. In the right light, you can actually see wisps of steam or vapor coming off the nozzle when printing wet material. This is water literally boiling out of your filament.

Excessive stringing that you can't tune out with retraction adjustments often indicates moisture. If your settings worked fine before and now everything strings, suspect moisture before changing your slicer profile.

On the Finished Print

Rough, matte surfaces where you expected smooth, glossy finishes suggest moisture damage. The texture comes from all those tiny steam bubbles disrupting the surface.

Weak parts that break at layer lines more easily than expected indicate poor layer adhesion from steam-disrupted bonding.

Inconsistent extrusion showing up as uneven layers, gaps, or varying line widths often traces back to wet filament.

Before You Start

Check filament brittleness. Some materials, particularly PLA, become more brittle when saturated with moisture. If your filament snaps easily when bent where it used to flex, moisture is likely the culprit.

Observe the spool. Filament that looks cloudy, has visible surface texture changes, or feels different than when fresh may have absorbed significant moisture.

How to Dry Wet Filament

If your filament has absorbed moisture, you can recover it. Several methods work:

Dedicated Filament Dryers

This is the safest and most reliable option. Filament dryers maintain precise temperatures with good air circulation, drying spools evenly without risk of melting. Many models let you print directly from the dryer, keeping material protected until it reaches the nozzle.

Typical drying times at appropriate temperatures:

• PLA: 4-6 hours at 45-55°C
• PETG: 4-6 hours at 60-70°C
• ABS: 4-6 hours at 60-80°C
• Nylon: 8-12 hours at 70-80°C (longer for heavily saturated spools)
• TPU: 4-6 hours at 50-60°C

Food Dehydrators

A budget-friendly alternative that works on the same principle. The challenge is that standard filament spools may not fit—you might need to modify the trays or remove center supports to create space. Temperature control is usually adequate for the lower-temperature materials like PLA.

Oven Drying (Use Caution)

Kitchen ovens can work but carry significant risks. Most ovens have inaccurate temperature controls with substantial fluctuations—the dial might say 50°C, but actual temperatures swing between 45°C and 65°C. That's enough to deform or even melt some filaments.

If you attempt oven drying:

• Verify actual temperature with a separate thermometer
• Use the lowest setting with the door cracked if needed
• Monitor constantly
• Understand you're risking the entire spool

I don't recommend this method when better options exist.

Important Drying Notes

Don't over-dry. Repeatedly drying filament with heat will eventually degrade the plastic. Prevention is better than cure—once you've dried filament, store it properly to avoid needing to do it again.

Temperature matters. Exceeding the glass transition temperature of your material will ruin the spool. PLA softens around 55-60°C; dry it at 45°C to be safe. Nylon can handle 80°C. Know your material's limits.

Preventing Moisture Problems

The best approach is preventing moisture absorption in the first place. Dry filament that stays dry will always produce better results than wet filament that's been dried.

Proper Storage

Sealed containers with desiccant are the gold standard. Options include:

• Original vacuum-sealed bags (reseal after use if possible)
• Airtight plastic bins with silica gel packets
• Vacuum storage bags you can reseal
• Purpose-built filament dry boxes

Desiccant selection matters. Indicating silica gel beads change color when saturated (often orange to green or blue to pink), telling you when they need regeneration. You can recharge them by heating to 100-120°C in an oven until they return to their dry color. Reusable desiccant is more practical than constantly buying new packets.

Monitor humidity. Small digital hygrometers are cheap and let you verify your storage is actually dry. Aim for below 20% relative humidity in your storage container—40% is acceptable for short-term storage of less sensitive materials like PLA.

During Printing

Don't leave spools out. That convenient rack holding five spools in the open air is slowly ruining all of them, especially in humid climates. Return spools to sealed storage when not actively printing.

Consider dry box printing. Some setups feed filament directly from a sealed dry box into the printer. This keeps the material protected until it enters the extruder, eliminating any exposure to ambient humidity during long prints.

Print fresh-opened spools first. If you open a new spool, use it for your most demanding prints while it's still factory-dry.

Environment Management

Room dehumidifiers help if you're running a print farm or workshop with multiple machines. Keeping the whole space at lower humidity reduces the rate at which exposed filament absorbs moisture.

Enclosures help. If your printer has an enclosure, humidity inside tends to stay lower than room ambient, especially during heated prints. Some users add small rechargeable dehumidifiers inside enclosures for additional protection.

Climate considerations. Here in Jacksonville, I treat filament storage as non-optional rather than nice-to-have. If you're in a similarly humid climate—Florida, the Gulf Coast, the Pacific Northwest—assume moisture is affecting your prints unless you're actively preventing it.

How Different Materials Respond

Understanding your specific material helps you prioritize storage and drying efforts:

PLA is the most forgiving. It absorbs moisture slowly and maintains printability longer than other materials. Still, PLA that's been sitting open for months in humid conditions will benefit from drying. Store it sealed, but don't panic if it gets some exposure.

PETG is more sensitive than PLA. It absorbs moisture gradually but the effects accumulate. Many print quality issues blamed on settings are actually moisture creeping into PETG that seemed fine last week.

Nylon requires military-grade discipline. Some nylon variants (PA6) absorb moisture so aggressively that they can't be left exposed even for a single print session in humid conditions. If you're printing nylon, drying and dry-storage aren't optional—they're essential for any print quality at all.

TPU falls somewhere in the middle. Its moisture sensitivity varies by formulation, but most TPU benefits from dry storage and occasional drying.

ABS absorbs moisture similarly to PETG. Keep it sealed, dry before printing if quality degrades, and don't assume its reputation for toughness extends to moisture resistance.

Quick Reference: Moisture Management

| Material | Moisture Sensitivity | Storage Priority | Drying Temp | Drying Time | |----------|---------------------|------------------|-------------|-------------| | PLA | Low-Medium | Standard | 45-55°C | 4-6 hours | | PETG | Medium | Important | 60-70°C | 4-6 hours | | ABS | Medium | Important | 60-80°C | 4-6 hours | | Nylon | Very High | Critical | 70-80°C | 8-12+ hours | | TPU | Medium-High | Important | 50-60°C | 4-6 hours |

What We Do at Mandarin3D

Managing filament moisture is part of producing consistent, high-quality prints. We store all materials in controlled humidity conditions and dry filament before use when necessary. Our BambuLab P1S and H2S printers produce excellent results partly because the material feeding into them hasn't been compromised by moisture.

When you order a print, you shouldn't have to worry about whether your part is weak because the filament was stored improperly. That's our job to manage.

Start With Good Habits

If you're printing at home, building good storage habits now prevents problems later. A sealed container with some silica gel costs a few dollars and saves frustration over ruined prints and wasted material.

If you're ordering prints, moisture management is one of the advantages of working with an experienced print service. We control the variables so you get consistent results.

Ready to order a print? Upload your model and we'll produce it with properly stored, dry filament—every time. Have questions about materials or print quality? Reach out. Understanding what affects your prints is part of the service.