Nylon Moisture Treatment — Complete Drying & Storage Guide

Nylon is notoriously hygroscopic, absorbing moisture from the air like a sponge. This moisture causes printing defects ranging from poor surface finish to complete print failure. The following drying, storage, and handling techniques apply to both FDM filaments and injection molding feedstock.

Why Nylon Absorbs Moisture

Nylon’s chemical structure contains amide groups that form hydrogen bonds with water molecules. This hydrophilic nature means nylon will absorb moisture until it reaches equilibrium with ambient humidity.

At 50% relative humidity, nylon can absorb:

• PA6: 2.5-3% moisture by weight
• PA66: 2.0-2.5% moisture by weight
• PA12: 1.0-1.5% moisture by weight

PA12’s lower absorption rate makes it preferable for humid environments.

Signs of Moisture Contamination

Visual Indicators

• Popping sounds during extrusion (steam bubbles)
• White residue or “blooming” on print surface
• Bubbles in extruded filament
• Stringing and oozing

Print Quality Issues

• Poor layer adhesion
• Rough, bumpy surface texture
• Reduced mechanical strength (up to 50% loss)
• Dimensional inaccuracy

Drying Methods Compared

Food Dehydrator

The most accessible option for most users:

Temperature	Duration	Suitability
70°C	6-8 hours	PA6, PA66
60°C	8-12 hours	PA12, sensitive
80°C	4-6 hours	Moisture-heavy

Pros: Inexpensive, effective, widely available
Cons: Limited capacity, manual monitoring

Dedicated Filament Dryer

Purpose-built solutions with precise control:

• Temperature control: 40-80°C
• Built-in humidity monitoring
• Spool rotation capability
• Direct feed to printer

Oven Drying

Use with caution:

1. Preheat to 70°C (never above 80°C for nylon)
2. Place spool on rack (not direct metal)
3. Prop door slightly open for moisture escape
4. Dry for 4-6 hours
5. Allow complete cooling before handling

Warning: Many ovens have temperature variance. Verify with thermometer.

Proper drying is essential before temperature calibration.

Optimal Storage Solutions

Vacuum Sealing

Most effective long-term storage:

1. Use vacuum bags designed for food storage
2. Add desiccant packets (silica gel)
3. Seal immediately after drying
4. Label with date and material type

Dry Box Systems

Active humidity control for frequent users:

• Passive: Airtight container with desiccant
• Active: Heated box with humidity control
• Hybrid: Combination with direct feed

Desiccant Types

Type	Capacity	Reusable	Cost
Silica Gel	Good	Yes	Low
Molecular Sieve	Excellent	Yes	Medium
Indicating (blue)	Good	Yes	Low

Prevention Best Practices

Handling Rules

1. Never leave filament exposed to air
2. Return to storage immediately after printing
3. Use dry boxes for humid climates
4. Monitor humidity with hygrometer

Environmental Control

• Print room humidity: Below 40% RH ideal
• Avoid printing during rain/humid days
• Air conditioning helps reduce humidity
• Consider dehumidifier for workshop

Testing for Moisture

The Simple Test

Heat your nozzle to printing temperature and extrude filament:

• Dry nylon: Smooth, glossy extrusion
• Wet nylon: Hissing, popping, bubbles, rough surface

Weight Measurement

For precise determination:
1. Weigh spool before drying
2. Dry completely
3. Weigh again
4. Calculate moisture percentage

Target moisture: Below 0.2% for optimal printing