Filament Moisture Problems and How To Fix Them

Moisture ruins more prints than bad slicer settings. Most people blame temperatures, retraction, or speed when a print looks rough, but wet filament is usually the real cause. Once the material absorbs water, the melt expands, pops, and throws off the entire extrusion process.

You get stringing, bubbles, weak layers, and a dull surface. In extreme cases, the filament hisses at the nozzle because steam is literally bursting out of it.

Why Filament Absorbs Moisture

PLA, PETG, ABS, and especially nylons pull moisture from the air. Some materials take longer than others, but every open spool will eventually get wet. Once that happens, the nozzle cannot extrude a stable line anymore, and the print loses strength fast.

The problem starts at the layer interface. Steam creates tiny voids. Even if the part looks fine on the outside, the mechanical strength can drop drastically.

How To Store Filament Correctly

For everyday materials, keep your filament below 30 to 40 percent humidity. The easiest way is to use airtight storage with silica gel. Replace or recharge the desiccant regularly, because it saturates quickly.

If you run a print farm or print often, use a dedicated dry box that keeps filament in a low humidity environment while feeding directly into the printer.

How To Dry Filament

If the filament crackles during extrusion, it is wet. Dry it before printing.

Here are proven temperature ranges:

• PLA: 45 to 55 degrees

• PETG: 50 to 55 degrees

• ABS: around 60 degrees

• Nylon: 70 to 80 degrees and longer drying time

Most materials need four to six hours. Nylon often needs more.

Dryers work best when they run during the entire print. Moisture can come back quickly, especially with hygroscopic materials like nylon and TPU.

How To Prevent Moisture Getting In Again

Drying a spool once is not enough if you leave it out in the open. The filament will absorb water again within hours.

Keep these rules simple:

• Store every spool airtight when not in use

• Keep desiccant refreshed

• Dry the filament right before printing if it sat out for a while

• Use an active dry box during long prints

If you print functional parts, do not skip the drying step. Moisture affects strength more than surface quality, and failure usually starts inside the layers long before it becomes visible.

Clean, strong prints do not only come from perfect slicer settings. They come from dry material, proper storage, and stable temperatures. Get moisture under control, and most of your extrusion issues disappear instantly.