How to dry wet PETG filament: temperature, time and method
Wet filament usually comes back after a proper drying. What ruins a spool for good is drying it wrong: too much heat fuses the coils together or warps the spool. So confirm that moisture is really the problem first, then pick the temperature and the method.
How to tell if your filament is wet
Water in the filament turns to steam in the hot nozzle, and the plastic comes out bubbly and uneven. The signs:
- Popping or hissing at the nozzle, sometimes with a wisp of steam.
- Stringing and oozing that retraction tuning does not fix. PETG strings a little anyway; wet, it gets much worse.
- A rough surface with bubbles or pinholes on the outer walls.
- Weak parts, with layers that split apart easily.
- Brittle PLA that snaps when you bend it. That can be moisture, age or stress from the winding; drying fixes some of these cases.
Quick test: heat the nozzle to printing temperature and extrude about 50 mm into the air. Bubbles, popping or steam mean moisture; dry filament comes out smooth and quiet.
Not every material suffers the same. Bambu Lab lists drying before use as required for TPU, PC, nylon (PA) and PVA, and recommended for PLA, PETG, ABS and ASA. Prusa agrees: PLA changes little with moisture, while nylon, PVA and TPU need drying more often. If you are still choosing a material, see PLA vs PETG.
Drying temperature and time by material
Each manufacturer tests its own filament, and the numbers do not match exactly. The table shows what three brands publish and the range that covers all three. If your spool has a data sheet, follow it; if not, start at the low end of the range.
| Material | Bambu Lab (forced-air oven) | Polymaker (data sheet) | Prusament | Range across the three |
|---|---|---|---|---|
| PLA | 50 °C · 8 h | 55 °C · 6 h | 45 °C · 6 h | 45–55 °C (113–131 °F) · 6–8 h |
| PETG | 60–65 °C · 8 h | 65 °C · 6 h | 55 °C · 6 h | 55–65 °C (131–149 °F) · 6–8 h |
| TPU | 70 °C · 8 h | 70 °C · 8 h | 60 °C · 4–6 h | 60–70 °C (140–158 °F) · 4–8 h |
| ABS | 75–85 °C · 8 h | 70 °C · 6 h | not listed | 70–85 °C (158–185 °F) · 6–8 h |
| ASA | 75–85 °C · 8 h | 70 °C · 7 h | 80 °C · 4 h | 70–85 °C (158–185 °F) · 4–8 h |
| PC | 75–85 °C · 8 h | 75 °C · 6 h | 85 °C · 5 h (PC Blend) | 75–85 °C (167–185 °F) · 5–8 h |
| Nylon (PA) | 75–85 °C · 8–12 h (fiber-filled PA) | 100 °C · 8 h (CoPA) | 90 °C · 6 h (PA11 Carbon Fiber) | 75–100 °C (167–212 °F) · 6–12 h |
Sources, checked November 2026: the Bambu Lab wiki (forced-air oven column), Polymaker's data sheets for PolyLite PLA, PolyLite PETG, PolyFlex TPU95, PolyLite ABS, Polymaker ASA, PolyLite PC and PolyMide CoPA (for example, the PolyLite PETG sheet), and Prusa's drying article.
Three rules apply to all of them:
- Do not go over the temperature. Above the recommendation, filament softens and the coils stick together (Prusa). PLA has the smallest margin.
- Do not stretch the time. Prusa warns against over-drying, and Bambu Lab notes that PC gets brittle after many heat-and-cool cycles.
- Keep nylon sealed from day one. According to Bambu Lab, after about three months in open air it becomes very hard to dry in an ordinary oven at 80–90 °C.
The spool has a limit too
Before you pick the filament temperature, check what the spool can take. Bambu Lab warns that some third-party spools deform at drying temperatures, and a warped spool jams on the holder and in the AMS. Two published limits: Bambu Lab's reusable spool handles drying at 80–90 °C; Prusament's current black spool goes up to 90 °C, but the older version with a cardboard core only to 45 °C unless a screw holds the sides together.
When the material asks for more than the spool can take, like the 100 °C on Polymaker's CoPA nylon sheet, move the filament to a spool that can handle it or stay at the spool's limit and accept a slower dry. If the brand does not state a limit, start low and look at the spool after the first hour.
Methods, from safest to riskiest
Filament dryer
The simplest route: the unit controls the temperature, and many let you print straight from it. Check the maximum temperature before buying, as Prusa advises: a dryer that tops out at 65 °C handles PLA and PETG, is borderline for TPU and falls short for ABS, PC or nylon.
Bambu Lab AMS 2 Pro and AMS HT
The AMS 2 Pro dries materials up to 65 °C: PLA, PETG and TPU (which, Bambu Lab says, may not dry completely in it). The AMS HT dries everything, including ABS, ASA, PC and nylon. In both, Bambu Lab lists 45 °C for 12 h for PLA and 65 °C for 12 h for PETG. On an X1, P1 or A2L, the AMS 2 Pro needs its own power adapter to dry.
The heated bed of an enclosed printer
Bambu Lab publishes a procedure for its enclosed printers (it does not work on open ones like the A1, A1 mini, P1P and A2L): unload the filament from the hotend, lower the bed, lay the spool flat, cover it with the filament box or a cover printed in PC, close the door and flip the spool halfway through, wearing gloves. The temperature is the plate's, so it is higher than an oven setting: 60–70 °C for PLA, 75–85 °C for PETG and 90–100 °C for ABS, ASA, PC and nylon, for 12 h; TPU, 80–90 °C for 12 to 16 h. On other brands, use this method only if the manufacturer recommends it.
Food dehydrator
It works with the middle trays removed so the spool fits, as Prusa describes. The catch is temperature: these appliances usually run low, so check the maximum in the manual and confirm it with a thermometer.
Kitchen oven, the riskiest
Here the manufacturers disagree. Bambu Lab advises against kitchen ovens and microwaves: heat near the elements is uneven and can melt the filament or the spool. Prusa accepts an oven with an external thermometer, because the thermostat swings more than filament tolerates and many ovens cannot go as low as PLA needs. If you use one, stabilize the temperature with the thermometer next to the spool before putting the filament in, keep the spool on the middle rack away from the element, and stay nearby.
After drying: how to store it
According to the Bambu Lab wiki, indoor air is usually at 45% to 65% relative humidity, and in it a freshly dried spool absorbs enough water to affect print quality within 2 to 12 hours, depending on the material. Below 20%, most filaments stay dry for 2 to 7 days, and the lower the humidity, the longer. Polymaker sets the same 20% ceiling for nylon. In practice:
- A sealed box or vacuum bag with desiccant, as Prusa recommends, plus a hygrometer inside to show when the desiccant is spent.
- Regenerate silica gel when it changes color: Bambu Lab says 80 to 90 °C, never above 100 °C, for 1 to 3 hours, in glass, ceramic or aluminum, never plastic.
- Nylon and TPU straight from dry storage, ideally printing with the spool inside the dry box or dryer.
Good storage also lets you use a spool to the end; to see how much is left, check how much filament is left on a spool.
What drying costs, and what not drying costs
Drying only uses electricity, and the math is the same as for the printer: watts ÷ 1,000 × hours × price per kWh. At the reference rate of $0.17/kWh and a $20 spool (the PLA reference price; PETG usually costs about the same):
| Situation (example) | Math | Cost |
|---|---|---|
| 100 W dryer running nonstop for 8 h (a ceiling: the heater cycles on and off) | 0.1 kW × 8 h × $0.17 | $0.14 |
| Printer bed for 12 h at a 120 W average (the calculator default) | 0.12 kW × 12 h × $0.17 | $0.24 |
| A 250 g, 8-hour PETG print lost to moisture | 250 g × $0.02 + 8 h × $0.17 | $6.36 |
| A spool fused in an oven that ran too hot | the whole spool | $20.00 |
The $0.17 per hour is the machine cost under the calculator defaults: a $600 printer with a 6,000-hour life, $0.05/h for maintenance and 120 W of electricity. The oven is left out because its draw varies too much between models; measure yours with a plug-in power meter. Electricity rates also vary a lot between states, so use the rate on your bill.
Even at the ceiling, one drying session costs less than 1% of the spool, and a single lost print pays for over 40 sessions in the example dryer. The electricity math in detail is in the guide to 3D printer electricity cost.
Frequently asked questions
Can I dry filament in the microwave?
No. Bambu Lab advises against it: a microwave heats unevenly and gives you no temperature control. You risk melting parts of the spool while others stay wet.
Does a new, sealed spool need drying?
Most of the time, no: brands like Polymaker dry their filament before packing it, and the sealed bag with desiccant is there to keep it that way until you open it. Dry it if the bag arrived punctured or the symptoms show up on the first print. For TPU, PC and nylon, Bambu Lab treats drying before use as required.
How many times can I dry the same spool?
Manufacturers do not publish a number. What they ask is to respect the temperature and the time: Prusa warns against over-drying, and Bambu Lab notes that PC gets brittle after many cycles. The way to dry less often is to store better.
Will drying fix PETG stringing?
It does when moisture is the cause. If dry PETG still strings, the problem is temperature, retraction or travel moves; the guide to PETG stringing covers the settings.
How long can a spool sit out during a long print?
By Bambu Lab's numbers, at 55% humidity a freshly dried spool starts causing problems within 2 to 12 hours, depending on the material. For long PETG, TPU or nylon prints, print with the spool inside the dryer or a dry box with a port for the PTFE tube.