If you’re figuring out how to dry filament without a dryer, use a food dehydrator first, a convection oven checked with a separate thermometer second, and a heated bed under an upturned cardboard box as the fallback. Run PLA at 45–55°C, PETG at 55–65°C and TPU at 60–70°C for about 6 hours, then weigh the spool to confirm.
The ranges span two vendor charts: Prusa’s drying guide at the low end and Snapmaker’s at the high end. Whatever the appliance, two rules decide whether it works: hold a steady temperature below the filament’s softening point, and give the moisture somewhere to go.
Prusa lists poor surface quality as usually the first sign of wet filament, followed by more stringing, weak layer adhesion, blobs and bubbling. Polymaker’s wet-filament page adds popping or hissing at the nozzle, and ranks nylon, PVA, TPU and PETG as the most moisture-sensitive and PLA as the least. The filament types comparison covers the rest.
What temperature should you dry each filament at?
Dry at the filament maker’s stated temperature and never above it: roughly 45–55°C for PLA, 55–65°C for PETG, 60–70°C for TPU, 80°C for ASA and 85–90°C for PC blends and carbon-fiber nylon. Hotter than that, the strands soften and stick together on the spool, and Prusa notes a shorter run won’t undo the damage.
| Material | Prusa (Prusament) | Snapmaker | Best no-dryer method |
|---|---|---|---|
| PLA | 45°C, 6 h | 55°C, 6 h | Dehydrator, heated bed + box |
| PETG | 55°C, 6 h | 65°C, 6 h | Dehydrator, oven |
| TPU | 60°C, 4–6 h | 70°C, 6 h | Dehydrator (bottom rack), oven |
| ASA | 80°C, 4 h | not listed | Convection oven |
| PC Blend | 85°C, 5 h | not listed | Convection oven |
| PA11 Carbon Fiber | 90°C, 6 h | not listed | Convection oven, long run |
Prusa’s figures are for Prusament, so for other brands start from the spool label or technical data sheet. Check the spool as well: Prusa rates its black spools made from October 2025 onward to 90°C, but older black ones only to 45°C unless a screw at least 65 mm long holds the two sides together. With an unrated generic spool, stay at the low end of the range.
Method 1: Food dehydrator, the closest thing to a real dryer
A food dehydrator pairs low, steady heat with forced airflow, which is what a filament dryer does. Polymaker’s wiki argues airflow matters more than heat because moving air carries moisture away, letting you dry cooler and gentler. Snapmaker goes further, saying dehydrators often beat entry-level filament dryers on temperature range, ventilation and evenness.
- Remove the trays or clip the tray webbing so a 1 kg spool sits flat, and keep that unit for plastics only from then on.
- Put a probe thermometer beside the spool, not by the dial. In CNC Kitchen’s drying comparison, a dehydrator set to 75°C measured about 65°C on the bottom rack and 55°C on the top. Use that gradient: PLA high, PETG and TPU low.
- Run 4–6 hours for PLA and PETG. CNC Kitchen found that was often enough, with negligible change after 12 hours, and a repeat run a week later pulled almost nothing more out.
The ceiling is temperature. ASA, PC and nylon need 80–90°C, and the same test found the dehydrator couldn’t adequately dry carbon-fiber nylon. Those go in the oven.
Method 2: Kitchen oven, only with a separate thermometer
An oven is the only household appliance that reaches ASA, PC and nylon temperatures, and the riskiest one for PLA. Prusa warns that home ovens are imprecise, that swings harmless to food can damage low-temperature filament, and that many can’t run low enough at all. Snapmaker adds that ovens can spike well past the setpoint and fuse a spool solid.
- Preheat the oven empty with a thermometer where the spool will sit. Watch a full heating cycle and note the peak, not the average.
- If the peak overshoots your target, that oven is out for that material. Snapmaker’s suggested setup is a convection oven with a dehydrate function at 50–60°C and a meat probe set to alarm at 65°C.
- Use the middle rack, never a tray directly over the bottom element.
- Vent it. CNC Kitchen opened the door periodically during its 85°C oven runs to let moist air out.
- Budget long runs for nylon. CNC Kitchen’s nylon spools were still losing weight after almost a full day at 85°C.
Stay home while it runs, and check the thermometer hourly the first time you use a given oven.
Method 3: Heated bed under a cardboard box
This is the least controlled option, but it works for PLA and, slowly, PETG. Snapmaker’s version: bed at 45–60°C, spool flat on the plate, an upturned cardboard box over it with small holes cut in the top and bottom edges, run for a few hours.
The bed setpoint is not the drying temperature. The flange on the plate sits near bed temperature while the top of the spool runs much cooler, so put a probe thermometer inside the box and flip the spool halfway. Keep PLA at or below a 55°C bed, since Snapmaker puts its glass transition around 60°C. For PETG, expect the air in the box to sit below Prusa’s 55°C target even at a 60°C bed, so run past 6 hours and weigh the spool to confirm progress.
Don’t seal the box or swap it for a plastic tub: Snapmaker warns that heat without airflow creates a humid pocket that bakes moisture back into the spool. An enclosed printer holds the heat better than an open bedslinger, one more point in the enclosure debate. Raise Z or park the toolhead so the box clears it, and don’t leave the printer heating unattended.
Do desiccant, rice, or vacuum bags dry filament?
Not quickly: they are storage tools. In CNC Kitchen’s test, spools held under vacuum from a single-stage pump lost only 0.1–0.2% of their weight over 10 days, plateauing around day five, while the dehydrator removed about twice that from PLA and PETG and nearly three times from ASA. A 2026 Hackaday vacuum write-up tested fruit and silica desiccant rather than filament; it found low pressure alone was no silver bullet and suggested, without yet testing it, that adding heat might be the best way to speed moisture removal.
Silica isn’t useless. CNC Kitchen found a sealed box with plenty of silica pulled a significant amount of moisture from undried PLA and PETG over a week, so a tote packed with desiccant is a slow, zero-heat fallback for those two. Regenerate the silica at 110°C for 2 hours once the box’s hygrometer reads above 10%, which is CNC Kitchen’s routine. Skip the rice-in-a-bag trick; none of these vendor guides recommend it.
Desiccant earns its keep after drying. Prusa recommends a closed box or vacuum bag with desiccant and, if space is short, giving that storage to the hygroscopic materials first.
How do you know the filament is actually dry?
Weigh it, then print it. CNC Kitchen recommends weighing to confirm drying has finished, and its vacuum-dried spools lost only 1–2 g each, so use the most precise scale you own. Weigh before drying and after each session; when the number stops dropping, the spool is as dry as that temperature will get it.
Then print the same retraction tower or two-pillar stringing test before and after, at identical settings. It passes when:
- the nozzle no longer pops or hisses
- the surface sheen is uniform, not rough and matte in patches
- strings are gone or down to thin wisps
If strings survive on a spool that has stopped losing weight, moisture is ruled out. Work through oozing vs stringing, rerun a temperature tower, and for PETG check the nozzle temperature by brand before blaming the spool again.
When does a filament dryer make more sense?
When you dry more than once a week, print TPU or nylon regularly, or live somewhere humid. Babysitting an oven costs an evening each time, and a dehydrator isn’t built to feed the printer while it dries. Most boxes in our filament dryer comparison top out at 70°C, which covers PLA, PETG and TPU but not ASA, PC or nylon.
FAQ
does new filament need to be dried
Usually not, if the factory seal is intact. Polymaker dries each spool before shipping, vacuum-seals it with a desiccant pack, and says an unbroken seal means it’s ready to print. Dry a new spool only if the bag was punctured or the first print shows popping, a rough surface or stringing your usual profile doesn’t produce.
can you over dry filament
Yes, Prusa warns against overdrying and recommends sticking to its listed times, though overheating does the more visible damage: above the rated temperature, filament softens and loops fuse on the spool. Keep each run near the vendor’s time and, as CNC Kitchen advises, stay at least a couple of degrees below the material’s glass transition temperature.
how long does dried filament stay dry
Only a few days in open air. In CNC Kitchen’s measurements, vacuum-dried spools left out regained almost exactly the moisture removed within about 100 hours. Move a dried spool into a sealed box or vacuum bag with desiccant as soon as it cools, and print nylon, PVA and TPU from a dry box whenever possible.
does wet filament cause stringing
Yes, and it is one of the earliest signs. Prusa lists increased stringing right after poor surface quality, and Polymaker describes wisps between parts plus popping at the nozzle as water flashes to steam. Dry the spool before touching retraction, or you’ll tune settings around moisture that stop working once the spool is dry.
Related across the network
- Creality K1 Stringing Fix: Retraction, Heat and Drying — crealityreviews.com
- Best Filament for Beginners: What to Buy First — 3dfilamentguide.com
