Filament drying guide: why, when, and how
Yes, you need to dry filament. Every common 3D-printing plastic absorbs moisture from the air, and once wet it prints badly: popping at the nozzle, heavy stringing, fuzzy surfaces and weak layer bonds. The fix is a few hours of heat — PLA at 40–50 °C, PETG at 60–70 °C, Nylon at 80–90 °C. The full per-material table is right below; the filament drying chart & timer has the same numbers as an interactive tool with a built-in countdown.
Wet filament symptoms
Moisture problems announce themselves while printing. Watch and listen for:
- Popping, crackling or hissing from the nozzle — steam bursting out of the melt. This is the clearest single sign.
- Heavy stringing and oozing that retraction tuning does not fix — water turns the melt runny and pressurised.
- Fuzzy, rough or unexpectedly matte surfaces, sometimes with tiny steam-bubble craters, where the same profile used to print clean.
- Weak, brittle parts — steam voids inside the bead break the layer bond, so wet parts snap along layer lines.
Nylon and PETG absorb moisture the fastest and show symptoms within days of humid storage; PLA is the most forgiving but not immune. If a spool that printed fine last month now strings and pops, dry it before touching any slicer setting.
Drying temperature and time per material
These are the consensus ranges from dryer and filament manufacturers (PrintDry, Polymaker and Bambu Lab datasheets all land here) — the exact same values the drying chart & timer uses.
| Material | Temperature | Time | Note |
|---|---|---|---|
| PLA | 40–50 °C | 4–6 h | — |
| PLA+ / silk PLA | 40–45 °C | 4–6 h | Heat-sensitive — stay at or below 45 °C or the spool turns soft. |
| PETG | 60–70 °C | 4–6 h | — |
| ABS / ASA | 65–80 °C | 2–4 h | — |
| TPU | 50–60 °C | 6–12 h | — |
| Nylon (PA) | 80–90 °C | 8–12 h | Extremely hygroscopic — dry immediately before printing. |
| PC | 95–100 °C | 6–12 h | Needs a true 100 °C dryer; most ovens overshoot, verify with a thermometer. |
When in doubt, dry longer rather than hotter — heat above the filament's glass-transition zone softens the wind on the spool and can fuse loops together. The timer on the drying chart page defaults to the middle of each range and keeps running across a refresh, so you can start it and walk away.
Drying methods compared
- Dedicated filament dryer — the right tool: accurate, sized for a spool, and many models feed the filament straight to the printer so it stays dry while printing. Check the maximum temperature before buying for Nylon or PC — some dryers top out at 70 °C.
- Food dehydrator — the budget favourite. The round trays fit a 1 kg spool once you remove a few layers, and the better models hold 40–70 °C accurately with a real thermostat. Don't reuse it for food afterwards.
- Kitchen oven — works in a pinch, with real caveats. Household ovens commonly swing ±10 °C around the set point: dangerous near PLA's 40–50 °C window and often unable to hold PC's 95–100 °C steadily. Verify the actual temperature with a separate oven thermometer, use the fan setting if available, and never leave it unattended.
Safety: spools deform before some filaments dry
Many plastic spools soften below the drying temperature of engineering filaments — Bambu Lab's own ABS spools, for example, are rated to roughly 70 °C, well under the 80 °C+ that ABS, Nylon and PC need. A deformed spool jams the wind and can weld loops of filament together, ruining the rest of the roll. Either transfer the filament to a metal or glass tray, or dry at a lower temperature for a longer time. Cardboard spools tolerate heat but scorch near 100 °C — right in PC territory, so keep them out of high-temperature cycles. Silk PLA has the opposite problem: stay at or below 45 °C or the spool itself turns soft.
How to dry a spool, step by step
- Confirm it is wet. Popping at the nozzle, heavy stringing, fuzzy surfaces or weak layer bonds. If in doubt, dry anyway — it does no harm.
- Look up the material settings in the table above or in the drying chart & timer.
- Check the spool rating. Many plastic spools soften around 70 °C; move the filament to a heat-safe tray if the target temperature is higher.
- Dry at temperature for the full time. Moisture leaves the core of the wind slowly — cutting the time short dries the outer loops only.
- Print immediately or store dry. Straight onto the printer, or into a sealed dry box with desiccant before it re-absorbs.
Storage: keep it dry so you dry less
Drying is the cure; storage is the prevention. Sealed bags or an airtight dry box with fresh desiccant keep a spool print-ready for months — aim for the humidity indicator to stay under 20% RH. Silica gel can be regenerated in the same dehydrator you dry filament with. Nylon and TPU deserve a dry box even mid-print: they can pick up enough moisture during a long print in a humid room to degrade the second half. Vacuum bags are fine for shelf storage but not airtight forever, so weigh or test long-stored spools before a critical print — the spool remaining calculator tells you what's actually on them.
Per-material quick links
Answer-first drying pages for each material — temperature, time, wet symptoms and spool-safety notes:PLA ·PETG ·ABS ·ASA ·Nylon ·TPU ·PC
Frequently asked questions
Do I really need to dry filament?
Yes, sooner or later. Every common 3D-printing plastic is hygroscopic — it absorbs water from the air, and at 200 °C+ in the hotend that water flashes to steam inside the melt. PLA tolerates weeks of shelf exposure; PETG, TPU and especially Nylon can pick up enough moisture in days to print badly. When in doubt, dry.
What are the symptoms of wet filament?
Popping, crackling or hissing from the nozzle while printing, heavy stringing and oozing, a fuzzy or rough matte surface instead of the usual finish, steam bubbles in extruded lines, and weak, brittle layer bonds. If a spool that printed fine last month now strings badly after storage, moisture is the first suspect.
How do I dry PETG filament?
PETG dries at 60–70 °C for 4–6 hours in a filament dryer or food dehydrator. Check the spool first — many plastic spools soften around 70 °C, so stay at the lower end of the range or move the filament to a heat-safe tray. PETG re-absorbs moisture within a day or two in humid rooms, so print from a dry box if possible.
What are the right filament dryer settings?
PLA: 40–50 °C for 4–6 h (PLA+ and silk PLA: keep it at or below 45 °C). PETG: 60–70 °C for 4–6 h. ABS/ASA: 65–80 °C for 2–4 h. TPU: 50–60 °C for 6–12 h. Nylon: 80–90 °C for 8–12 h, dried immediately before printing. PC: 95–100 °C for 6–12 h. Longer and cooler beats shorter and hotter.
Can I dry filament in a kitchen oven?
It works, but household ovens commonly swing ±10 °C around the set point — risky near PLA’s 40–50 °C range and often unable to hold PC’s 95–100 °C steadily. If you use an oven, verify the real temperature with a separate thermometer and never leave it unattended. A filament dryer or food dehydrator with a real thermostat is the safer option.
Does drying fix old or brittle filament?
Drying fixes moisture, nothing else. PLA left for years can become brittle from physical aging, not just water — that filament may snap in the Bowden tube even after drying. Test a meter of it by hand after drying; if it still snaps easily, the spool is past saving.