How to dry and store 3D printer filament
Most 3D printing filaments pull water out of the air. A spool left open for a few days, or a few hours for nylon, can start printing with stringing, bubbles and weak layers even though nothing in your slicer changed. The fix is simple: dry the filament at the right temperature, then keep it dry. This guide covers which materials are most sensitive, how long to dry each one, and how to store spools so you only have to dry them once.
Why filament absorbs moisture
Most FFF plastics are hygroscopic, which means they attract and hold water molecules from the surrounding air. How much they take up, and how fast, depends on the polymer. PLA absorbs slowly and its properties change relatively little. Nylon absorbs water quickly enough to print noticeably worse within hours of being left out, and Prusa notes that badly stored nylon can take up water weighing as much as 10% of the filament.
The problem shows up at the nozzle. When wet filament is heated past its melting point, the absorbed water turns to steam inside the molten plastic. That steam expands, leaves voids and bubbles in the extrusion, and disrupts the steady flow the slicer expects. Wet filament also bonds poorly between layers, so the finished part can be weaker even when it looks acceptable.
Signs your filament is wet
Wet filament produces a recognizable set of symptoms. If you see several of these at once on a spool that used to print well, dry it before changing any settings.
Popping, hissing or steam at the nozzle
Small pops or crackles during extrusion, sometimes with visible wisps of steam, are water boiling out of the plastic. This is the most reliable sign.
Stringing and oozing that was not there before
Steam pressure pushes extra plastic out of the nozzle during travel moves, so retraction settings that used to work stop working.
Rough, bubbly or blotchy surfaces
Walls show tiny pits, zits and uneven texture. Glossy materials such as PETG can turn dull or hazy.
Weak layers and brittle parts
Poor layer adhesion makes parts split along layer lines. Some wet filaments also become brittle on the spool and snap in the feed path.
Which materials are most sensitive
Every filament benefits from dry storage, but some punish neglect much faster than others. Prusa's drying guide singles out nylon (PA), polypropylene, PVA and BVOH as highly hygroscopic and names TPU among the filaments that most often need drying, and most filament makers give similar advice.
Very sensitive: nylon, PVA, BVOH, PC and TPU
These can go bad in hours to days of open air. Dry them before printing, even from a freshly opened bag, and print them from a dry box when you can. The nylon filament guide covers the extra steps nylon needs.
Moderately sensitive: PETG, ABS and ASA
These tolerate a few days out, but a spool that has sat open for weeks usually prints noticeably better after drying. PETG is the one most people notice first, through extra stringing.
Least sensitive: PLA
PLA absorbs moisture slowly and many spools print fine for months. It still degrades eventually, and old PLA that snaps easily or strings heavily is often just wet.
Drying temperatures and times by material
The goal is to heat the filament enough to drive the water out without softening the plastic so much that the windings stick together. Stay below the upper end of each range, and treat the times as starting points: a spool that has been open for months may need the longer end, while a lightly exposed one may be fine sooner. Always check the maker's data sheet for your specific spool, since blends and fills can change the limits. These values match the drying column in our filament settings cheat sheet.
| Material | Temperature | Time | Sensitivity |
|---|---|---|---|
| PLA | 50 to 55°C | 4 to 8h | Low |
| PETG | 60 to 65°C | 4 to 8h | Moderate |
| ABS / ASA | 65 to 80°C | 4 to 8h | Moderate |
| TPU | 65 to 75°C | 8 to 10h | High |
| Nylon (PA) | 70 to 80°C | 8 to 12h | Very high |
| PC | 70 to 80°C | 6 to 8h | High |
| PVA / BVOH | Per maker | Per maker | Very high |
Water soluble supports are the exception to a single rule, because makers disagree widely. eSUN calls for 45°C for more than 10 hours on its PVA, Bambu Lab lists 55°C for its Support for PLA, and Bambu Lab lists 75 to 85°C for its PVA. Follow the exact value printed on your spool or data sheet rather than a generic chart, since the wrong temperature can soften or damage a soluble support filament.
Carbon fiber and glass fiber blends dry at the settings of their base plastic: PLA-CF like PLA, PETG-CF like PETG, PA-CF like nylon, unless the maker lists something different.
Filament dryer or kitchen oven?
You can dry filament in a kitchen oven, but it is the riskiest method. A dedicated dryer is built for exactly this job and costs less than a few ruined spools.
Why ovens are risky
Home ovens are designed for cooking, not for holding a precise low temperature. Many cannot run steadily as low as PLA needs, and their thermostats cycle well above the set point. A swing of 10°C that a casserole never notices can fuse PLA windings together or deform a plastic spool. Prusa recommends checking the real temperature with a separate thermometer before trusting an oven with filament.
What a dryer does better
A filament dryer holds a set temperature, circulates warm air around the spool, and usually runs on a timer so you can leave it overnight. Many models also let you print straight out of the box, which is ideal for nylon and TPU. Before buying, check the maximum temperature: some budget dryers top out around 55 to 65°C, which covers PLA and PETG but not nylon or PC.
Other options
Some printers and multi material systems, such as Bambu Lab's AMS 2 Pro and AMS HT, include a drying function. A food dehydrator with enough internal height for a spool can also work, as long as you verify its real temperature.
Browse and compare current models on our filament dryer price page, or see all printing gear.
Storing filament so it stays dry
Drying fixes a wet spool. Storage keeps it from getting wet again, so you are not drying the same spool every week.
Sealed bags
Resealable or vacuum storage bags are the cheapest option. Put a dried spool in with a desiccant pack and press or pump the air out. This works well for spools you use occasionally.
Airtight boxes with desiccant
A plastic tote or cereal style container with a good gasket holds several spools. Add a generous amount of silica gel and a cheap digital hygrometer so you can see when the desiccant is used up. Color changing silica gel makes this easy to check at a glance.
Humidity targets
For long term storage, aim for about 10 to 20% relative humidity inside the container, which is what Polymaker and Sunlu storage boxes are designed to reach. Prusa suggests below 30% for PLA, ABS and ASA, and below 20% for PETG, TPU, PC and water soluble supports. Nylon benefits from the lowest humidity you can manage.
Recharging desiccant
Silica gel is reusable. Once it is saturated, dry it out following the maker's instructions, then return it to the box. A hygrometer reading that creeps upward is the signal that it is time.
Compare dry boxes, vacuum bags and desiccant on the filament storage page.
Printing from a dry box
For the most sensitive materials, drying before a print is not enough on long jobs. A nylon or TPU spool sitting in open air for a 20 hour print can pick up enough moisture to hurt the second half of the part. Printing from a dry box solves this: the spool sits in a sealed container with desiccant, and the filament feeds to the printer through a PTFE tube and a sealed fitting.
Many filament dryers double as dry boxes and can keep heating during the print. Passive dry boxes, such as those from Prusa, do not dry filament on their own. They only hold humidity low, so dry the spool first and then load it.
The simple routine
Dry a new or suspect spool at its listed temperature, print sensitive materials from a dry box, and put every spool back in a sealed bag or box with desiccant when you are done. That habit prevents most mystery stringing and weak parts.
Compare Filament Dryer Prices
See live prices on filament dryers from the major brands, check maximum temperatures before you buy, and pair one with dry storage for the spools you print most.
Compare Filament Dryer Prices