This guide covers active drying: the actual process for driving moisture back out of a spool that has already absorbed it. That is a different job from the filament storage guide, which covers prevention (sealed containers, desiccant, keeping filament dry before it ever gets wet), and from the wet filament symptoms guide, which helps you confirm a spool is actually wet in the first place rather than diagnosing a different print problem. If you have already ruled out other causes and confirmed the filament is wet, this is where you fix it. For background on how different filament types compare before you buy more, see the filament types guide.
Why drying works
Hygroscopic filaments like PETG, nylon, TPU and PC pull water molecules into the plastic itself, not just onto the surface, which is why wiping a spool down does nothing. Water boils off at a temperature far below any of these materials’ printing range, so holding the spool at a moderate, sustained heat for several hours gives that trapped water time to migrate out and evaporate without approaching the plastic’s melting point. The heat does not need to be anywhere near printing temperature to work. It just needs to be applied for long enough and consistently enough for the moisture to fully escape.
Method 1: food dehydrator
A food dehydrator is the cheapest way most people already have on hand to dry filament, since it is built to hold a low, fan-assisted heat for hours at a time, which suits PLA, PETG and TPU well and can handle ABS or ASA if it reaches a high enough temperature. Most countertop dehydrators top out around 70 degC, which comfortably covers PLA, PETG and TPU but is often too low for nylon or PC. If your dehydrator cannot reach those higher numbers, extend the drying time rather than assuming it worked, or switch to a hotter method for that specific spool. Check that the trays are wide enough for a spool to sit upright or lie flat without touching the heating element, and treat the unit as filament-only rather than swapping it back to food afterward, since plastic residue and fumes are a real, if smaller, concern than with an oven.
Method 2: dedicated filament dryer or heated dry box
A filament dryer or a heated dry box is built for this exact job. The chamber is sized for a spool, the thermostat holds a steady temperature far more reliably than a kitchen oven, and many models let you pick the material and get a preset time and temperature instead of looking it up yourself. Several dry boxes also let filament feed straight from the box into the printer once drying finishes, so the spool never gets a chance to reabsorb moisture between the two steps. The tradeoff is cost, and on cheaper units, a ceiling temperature that may not reach what nylon or PC need, so check the specification before assuming a budget dryer can handle every material you own.
Oven drying risks
A kitchen oven is not built for this job and carries three real risks. First, fire: ovens hold heat close to a heating element, plastic can scorch or ignite if it touches that element or is left unattended too long, and a gas oven should be avoided outright since it adds combustion moisture on top of the fire risk. Second, overshoot: consumer ovens commonly run 5 to 20 degC hotter than the dial suggests, which is enough to fuse a PLA spool solid or scorch a nylon one if you trust the built-in display instead of an independent thermometer. Third, food contact: materials like ABS and nylon can give off irritating fumes when heated, and drying them in the same oven you cook food in risks leaving residue and odor behind, so ventilate the kitchen during and after, and treat a dedicated toaster oven kept only for filament as the safer long-term setup.
Using a kitchen oven safely
If a dedicated dryer or dehydrator is not an option, an oven can work with care. Preheat to the target temperature and confirm it with an independent oven thermometer placed near the filament, not the built-in display. Crack the door open slightly, a wooden spoon works well as a doorstop, so escaping moisture does not just recirculate, and keep the filament away from direct contact with heating elements, fans, or oven walls. For anything drying above roughly 60 degC, especially nylon, ABS or PC, strip the filament off its plastic spool onto a cardboard tube or a metal spool rated for the temperature, since ordinary plastic spools can warp or soften well before the filament itself is dry. Never leave the oven running unattended with filament inside, and avoid drying PLA in a full-size oven at all if you have another option. PLA softens close to the same range often used to dry other materials, so a small overshoot fuses the spool instead of just drying it.
Drying temperatures and times by material
These are starting ranges gathered from manufacturer guidance and drying references, not exact universal numbers, since brand, moisture level and spool size all shift the real answer. PLA dries at roughly 45 to 55 degC for 4 to 8 hours. PETG needs a bit more, around 55 to 70 degC for 6 to 8 hours. ABS and ASA both dry around 70 to 80 degC for 4 to 8 hours. TPU stays low, around 40 to 50 degC for 4 to 6 hours, since its softness makes it more sensitive to heat than its chemistry alone would suggest. Nylon needs the most: 70 to 95 degC for 6 to 12 hours, with the long end reserved for a badly saturated spool or a large reel. PC sits close to nylon, typically 70 to 100 degC for 6 to 8 hours. Check the spool label or the manufacturer’s technical data sheet first, since a specific product can call for a different number than the general range for its material family. Composite filaments can shift this too: wood-filled PLA is more hygroscopic than plain PLA even though it dries in the same temperature range, so see the wood filament guide for its specific storage and drying notes. PVA support filament is even more moisture-sensitive than any material on this list and needs drying before nearly every session rather than only when problems appear; see the PVA filament guide for its specific numbers.
Signs you have overdone it
Drying is not something to leave running indefinitely. A spool dried too long or too hot can come out more brittle than it went in, since sustained heat breaks down the polymer chains in a way that can leave a print looking similar to a wet-filament defect, just from the opposite cause. PLA and TPU show this fastest because they soften at relatively low temperatures. If a spool comes out of the dryer discolored, smells stronger than usual, or feels tacky rather than dry, let it cool fully before judging it, and treat repeated over-drying as a reason to lower the temperature or shorten the time next round rather than a reason to keep pushing the same settings.
Filament drying checklist
- Confirmed the filament is actually wet rather than diagnosing a different print problem.
- Method chosen based on the material’s temperature needs, not just what is on hand.
- Independent thermometer used to verify actual oven or dehydrator temperature.
- Filament removed from a plastic spool before high-temperature drying above roughly 60 degC.
- Oven never left unattended, and never reused for food without full cleaning and ventilation.
- Dried filament moved straight into sealed, desiccant storage to avoid reabsorbing moisture.