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Filament Guide  ·  Print3DBuddy

Wet Filament: How to Identify, Dry, and Store Filament Properly

One of the most frustrating 3D printing problems to diagnose is wet filament. The symptoms look like a dozen different things - stringing, poor surface quality, blobs, brittle prints, crackling sounds - and people often spend hours tweaking slicer settings trying to fix something that is actually a materials storage problem.

This guide covers how to identify wet filament, how to dry it out, and how to store it so the problem does not come back.

Why Moisture Ruins Filament

Most 3D printing filaments are hygroscopic - they absorb moisture from the air over time. When that moisture gets into the filament and you heat it to printing temperature, the water turns to steam inside the nozzle. That steam creates tiny bubbles and pressure spikes in the melt zone, causing a range of visible problems:

It is not a sign that your filament is ruined. In most cases, drying it properly will restore it to its original quality.

Which Filaments Are Most Affected?

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 / 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.

How to Tell If Your Filament Is Wet

Sounds:

Visual signs while printing:

Signs in the finished print:

When in doubt, listen. A dry spool should extrude almost silently. Crackling means moisture.

How to Dry Filament

Option 1: Dedicated Filament Dryer (Best)

A dedicated filament dryer (like the Sunlu S1 Plus or eSUN eBOX) is the easiest and safest method. Set the temperature, set a timer, done. Many models let you print directly from the dryer while it runs, which helps with long prints on sensitive materials.

See the best filament dryers guide for a comparison of popular options.

Option 2: Food Dehydrator

A food dehydrator works well and is often cheaper than a dedicated dryer. Make sure it fits your spool and can reach the required temperature.

Drying temperatures by material:

Filament Temperature Time
PLA 45-50C 4-6 hours
PETG 65C 4-6 hours
ABS / ASA 70-80C 4-6 hours
TPU 45-50C 4-6 hours
Nylon 80-90C 8-12 hours

Do not exceed these temperatures. PLA will deform if dried too hot, and most spool plastic softens around 70-80C.

Option 3: Oven

A kitchen oven works but requires care. Most ovens are inaccurate at low temperatures - the actual temperature can be 20-30C off the dial setting. Use an oven thermometer to verify before putting filament in. Leave the door slightly ajar to let moisture escape. Not recommended for PLA due to warping risk.

Option 4: Airtight Box With Desiccant

This will not dry filament quickly, but placing a wet spool in an airtight box with plenty of fresh silica gel desiccant will slowly pull moisture out over several days. Lowest effort, slowest result.

How to Store Filament

The Basic Setup: Airtight Container + Desiccant

The minimum you need:

  1. An airtight container - a large zip-lock bag works, but a sealed plastic storage box is better
  2. Silica gel desiccant packets - absorb moisture inside the container

Silica gel desiccant packs are cheap and reusable - bake at 120C for a few hours to regenerate when saturated. Colour-indicating silica gel changes colour when full, so you can see at a glance whether it needs regenerating.

Dedicated Filament Dry Boxes

Purpose-built dry boxes are a step up from zip-lock bags:

Vacuum Bags

Vacuum storage bags remove air entirely. Excellent for long-term storage of spools you won't use for months.

Practical Storage Tips

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.

Store in a cool, dry place. Avoid garages or sheds with temperature swings - condensation forms when temperatures change rapidly.

Buy a cheap hygrometer. A digital hygrometer (~£5) inside your storage box shows the humidity level. Aim for below 15% RH.

Label your desiccant. Note the date you last regenerated it. Replace or regenerate every 3-6 months depending on your climate.

For Nylon and TPU, dry before every long print regardless of storage conditions. These materials absorb moisture fast enough that even well-stored spools benefit from a drying session before a long print.

Quick Checklist

  1. Hear crackling or popping while printing? Dry the filament before continuing
  2. Identify the material - is it moisture-sensitive?
  3. Dry at the correct temperature and time for your material (see table above)
  4. Store in an airtight container with desiccant after drying
  5. Keep filament off the printer between sessions
Joshua Spencer

Written by Joshua Spencer

Joshua has spent years working as a 3D printer technician - calibrating and repairing FDM machines professionally across multiple industries. He runs Print3DBuddy to share practical, no-nonsense guidance based on real hands-on experience.