Most filaments absorb moisture from the air. Nylon, TPU and PETG pick it up fastest, but even PLA degrades after weeks on an open spool. When wet filament hits a hot nozzle, the water boils, and the print shows it.
Signs your filament is wet
- Popping or crackling sounds at the nozzle
- Heavy stringing and fuzzy surfaces that tuning will not fix
- Rough, bubbly or matte patches on glossy materials
- Brittle filament that snaps on the spool, or weak, delaminating parts
How to dry it
A dedicated filament dryer holds a steady low temperature with airflow for several hours. Typical starting points are around 45 to 55 °C for PLA, 60 to 65 °C for PETG and 70 to 80 °C for nylon, but the manufacturer's recommendation always comes first. Do not use a kitchen oven: hot spots can warp the spool and soften the filament.
How to keep it dry
Store open spools in sealed bags or bins with fresh desiccant, and feed moisture-sensitive materials from a dryer box while they print. Vacuum storage bags keep spools ready to run between jobs.
