Wet filament is a spool that has pulled moisture out of the air and into the plastic. The water boils at the nozzle, so you hear popping or hissing, the surface turns cloudy or rough, and the print strings and loses strength. Per Bambu’s dry-filament guide, the fix is heat held low and steady long enough to drive the water back out.
A wet spool can fool you, because the print fails in ways that look like a bad profile. Check for the moisture signs before you blame the slicer.
Your material sets how fast it goes wet. Nylon and PETG absorb the most, TPU and ABS some, and PLA the least.
The causes, ranked
| Likely cause | Fix | Severity |
|---|---|---|
| Filament stored open or in humidity | Store spools sealed with desiccant at low humidity. | hi |
| Spool left on the printer | Dry the spool before you print, and take it off the printer when done. | hi |
| Poor storage container | Move spools to an airtight bin with fresh desiccant. | md |
| Dried then left out again | Put the spool back in sealed storage the moment the print ends. | md |
| Old or hygroscopic material | Dry nylon, PETG, and TPU often, since they pull water fast. | lo |
First fixes to try
Dry the spool, then check the signs against a fresh print.
Dry the spool
Run the spool in a filament dryer or food dehydrator at the material temperature for 4 to 8 hours.
Check the signs
Reprint and listen for popping, look for a cloudy surface, and check for strings between moves.
Print from the dryer
For PETG, nylon, or TPU, print straight from the dryer so the spool stays warm and dry.
Store it sealed
Put the spool in an airtight bag or bin with desiccant the moment the print ends.
When quick fixes are not enough
When one dry does not hold, the storage and the drying setup are the next place to look.
Refresh the desiccant
Recharge or replace the desiccant, since spent beads let humidity climb back into the bin.
Add a hygrometer
Put a small hygrometer in the storage bin so you can see when the humidity rises.
Dry longer for nylon
Nylon holds the most water, so run it 8 to 12 hours and store it under 20 percent humidity.
Material differences
Nylon and PETG absorb moisture the fastest, so they go wet in days if left open and need a longer dry. TPU and ABS sit in the middle. PLA absorbs the least and tolerates more open-air time, but it still goes wet in a humid room. Dry at the temperature the maker lists, since some blends soften lower than others.
Mistakes that undo the fix
A few common choices dry the spool once and let it go wet again.
Avoiddo not
- Drying the spool, then leaving it open on the printer.
- Storing spools with spent desiccant, which holds moisture in.
- Drying nylon or PETG too short to get the water out.
- Blaming the slicer for stringing before you check for moisture.
Key takeaways
- Wet filament pops, strings, and prints rough from absorbed water.
- Dry the spool at its material temperature for 4 to 8 hours.
- Store it sealed with desiccant the moment the print ends.
- Nylon and PETG absorb the most; PLA the least.
For the hairs it leaves, the stringing guide covers moisture-driven strings, and the filament storage guide covers the sealed-container setup.
Related guides
Related
More in this area
Cross-reference
Sources & methodology
3 citations · reviewed 2026-07-10- 01Bambu Lab Wiki: Dry filament (per-material drying table)accessed 2026-06-29Tier 1
- 02All3DP: How to dry filament (PLA, ABS, nylon)accessed 2026-07-09Tier 2
- 03All3DP: Hygroscopy in 3D printing (which filaments absorb moisture)accessed 2026-07-09Tier 2