How to Dry Filament

Is Your Filament Wet?

Filament absorbs moisture from the air, some materials within hours of opening the bag. When that water hits a 200°C+ nozzle it boils instantly, and the steam pockets wreck the extrusion. The symptoms are distinctive:

• Popping, crackling or hissing from the nozzle while printing. That is literally steam escaping.
• Heavy stringing and oozing that your usual retraction settings suddenly cannot control.
• Rough, fuzzy or bubbly surfaces where prints used to come out smooth.
• Weak layer adhesion: parts snap along layer lines at loads they used to survive.
• Brittle filament: PLA that snaps when you flex it near the spool has usually been wet (or is just old).

Two or more of these together, on filament that has been out of a sealed bag for a while, is wet filament until proven otherwise. Drying is cheap; chasing phantom slicer settings is not. When in doubt, dry it: even brand-new spools can arrive wet from months in a warehouse.

Drying Temps & Times by Material

Low heat for a long time is the whole trick. Too little heat and the water stays in the polymer; too much and you deform the filament or fuse the spool. These are the safe windows:

These match the ranges Prusa and Bambu Lab publish for their own materials [1] [2]. If your dryer only reaches 55°C, PETG and nylon will still improve with a longer run, just more slowly.

Drying Methods, Best to Worst

Purpose-built filament dryer. The right tool. Holds an accurate low temperature, most models show humidity, and many have a feed port so you can print straight from the dryer. That last part matters for nylon and PETG, which start re-absorbing moisture the moment they come out.

Food dehydrator. Nearly as good and often cheaper secondhand. Most hold 45–70°C accurately, which covers PLA through TPU. You may need to remove trays to fit a spool.

Kitchen oven. Works, with two big caveats. Most home ovens cannot reliably hold a temperature below 60°C, and the real temperature can spike far above the dial setting. Use a separate oven thermometer you trust, keep the door cracked so moisture escapes, and never walk away from a PLA spool in an oven. A warped, fused spool is the usual price of skipping the thermometer.

What about rice or a bag of desiccant? Desiccant slows moisture uptake; it does not meaningfully pull water back out of a soaked spool at room temperature. Rice is worse and sheds starch dust. Use heat to dry, desiccant to keep dry.

Never microwave filament. Microwaves heat unevenly and can melt or ignite the spool.

Drying With Printer Hardware

Bambu Lab AMS and AMS lite: neither has a heater. They keep dry filament dry with desiccant, and that is all. If a spool already prints wet, running it through the AMS changes nothing. The AMS 2 Pro is different: it added an active drying mode that heats the chamber, so it can genuinely rescue a damp spool.

Bambu X1/P1 heatbed method: Bambu documents a chamber-drying trick using the heated bed with the spool placed on it and drying mode in the settings [2]. It works, but it ties up the printer for hours and heats less evenly than a dryer. Fine occasionally; buy a dryer if you do it weekly.

Creality CFS: like the standard AMS, it is a sealed feeder with desiccant, not a dryer. There is no heating element. Dry the spool first, then let the CFS keep it that way.

Heated dry boxes: some enclosures and dry boxes include a low-watt heater. Treat the spec sheet with suspicion: if it cannot state a controlled temperature, it is a storage box, not a dryer.

Can You Over-Dry Filament?

Time is not the problem; temperature is. Leaving PLA at 50°C for 12 hours instead of 8 does no measurable harm. What actually damages filament:

• Exceeding the softening point. PLA above roughly 60°C softens, sags between spool wraps and can fuse into an unusable brick. TPU deforms above 75°C.
• Repeated aggressive cycles. Cooking any polymer near its limit over and over slowly embrittles it. If a spool needs drying every week, fix the storage instead.

So the practical answer: set the temperature from the table, and do not stress about a few extra hours.

Keeping It Dry Afterwards

Drying is the cure; storage is the prevention. A dried nylon spool left on an open shelf is wet again within a day or two, PETG within weeks. Vacuum bags or sealed boxes with desiccant, plus a cheap hygrometer to keep them honest, stop the cycle. The full setup, including humidity targets per material and how to recharge saturated desiccant, is in the filament storage guide.

FAQ