Most filaments slowly absorb moisture from the air. Wet filament causes stringing, bubbles, popping sounds and weak, rough prints. The fix is simple: store filament dry, and dry it when it has picked up moisture.
About this guide: Drying temperatures come from Prusa’s official drying filament article for Prusament. Checked in October 2026. “Check price” links go to the official store and may be affiliate links, which never changes the advice.
Signs your filament is wet
- Popping or hissing sounds from the nozzle
- More stringing than usual
- Bubbles, rough surfaces or weak layers
- Filament that snaps easily (common with old PLA)
Drying temperatures
| Material | Temperature | Time |
|---|---|---|
| PLA | 45 °C | 6 hours |
| PETG | 55 °C | 6 hours |
| TPU | 60 °C | 4–6 hours |
| ASA | 80 °C | 4 hours |
| PC Blend | 85 °C | 5 hours |
| PA11 Carbon Fiber | 90 °C | 6 hours |
Don’t go hotter than recommended. Prusa warns that too much heat softens the filament so the windings stick together. Also check that the spool itself can take the heat.
How to dry filament
- A filament dryer is the easiest option. Many can also feed the printer while drying.
- Some multicolor systems dry filament, such as Bambu Lab’s AMS 2 Pro and AMS HT.
- A convection oven works, but many kitchen ovens are not accurate at low temperatures, so check with a thermometer.
How to store it
- Keep spools in a sealed box or bag with desiccant.
- Put opened spools back in storage after printing.
- A cheap hygrometer in the box tells you when the desiccant needs replacing.
Frequently asked questions
Does filament go bad? Why does my old PLA snap?
It can. PLA that snaps when you bend it is a frequent complaint on the Bambu Lab, UltiMaker and LulzBot forums. Owners blame moisture, slow aging of the plastic, and filament left bent in the feed tube; breaks often show up in the section inside the tube while the rest of the spool stays flexible. A Bambu Lab forum poster points out that no manufacturer has published a long-term storage study, so there is no official shelf life to go by.
Drying brings some brittle spools back, and owners report mixed results. Sealed storage with desiccant slows the problem, and unloading filament after a print stops it from sitting bent in the tube. If a dried spool still snaps, keep it for test prints. See how to store and dry filament.
Sources: Bambu Lab forum.
How do I know if my filament is wet, and how do I dry it?
Prusa says the first sign is usually a poor surface finish, followed by weak layer adhesion, blobs, and bubbling or smoke at the nozzle. Wet filament also strings much more. Prusa names nylon, PVA and TPU as the materials that most often need drying.
Prusa’s drying settings for its own filaments are PLA 45 °C for 6 hours, PETG 55 °C for 6 hours, TPU 60 °C for 4–6 hours, ASA 80 °C for 4 hours and PC Blend 85 °C for 5 hours. Do not go hotter, or the filament softens and the windings stick together. Home ovens often lack accurate temperature control, so Prusa recommends checking with a separate thermometer. It also says food dehydrators usually run too cool for filament. Check that your spool can take the heat too: older cardboard Prusament spools are only rated to 45 °C.
Sources: Prusa Knowledge Base.
Does PLA need drying, and how should I store filament?
PLA is less sensitive than most materials. Prusa says it does not change much when it takes up humidity, though on multi-tool printers like the Prusa XL it recommends drying PLA as well, since even PLA can pick up enough moisture to cause problems there. Nylon and TPU need much more care.
For storage, Prusa recommends a closed box or bag with desiccant inside, and mentions vacuum bags with desiccant and dry boxes. Owners on the Bambu Lab forum report that household vacuum bags do not keep air out perfectly over months, so a spool that has been stored a long time may still need drying before an important print.
Sources: Prusa Knowledge Base, Bambu Lab forum.