Filament drying guide — temperatures, times and methods

Every 3D printing filament is hygroscopic to some degree — it absorbs water from the air. Wet filament prints poorly: stringing, bubbles in the extrusion, weak inter-layer bonding, gappy walls. The fix is simple and free: dry it before printing. This guide is the definitive table of temperatures and times for every common filament, plus the cheapest ways to actually do the drying.

Why drying matters

When wet filament hits the melt zone (200–280 °C), absorbed water flashes to steam inside the molten plastic. The steam:

• Disrupts extrusion, creating inconsistent line widths and gaps.
• Forms micro-bubbles that lower mechanical strength by 20–50%.
• Hydrolyses the polymer chains in PETG, ABS, PC, and nylon — permanent degradation.
• Causes stringing and oozing that no slicer setting can compensate for.
• Hisses, pops, or steams audibly at the nozzle.

Drying restores the polymer's print performance — but it can't reverse hydrolysis, so badly degraded nylon may never print like new again.

The complete drying table

Sources cross-checked against PrintDry, Polymaker, Bambu Lab, and individual filament manufacturer datasheets. Use the longer end of the range for fully-saturated filament.

How to tell if your filament is wet

1. Audible test: heat hotend, push 100 mm of filament through. Listen. Hissing, popping, or "fizzing" = wet.
2. Visual test: watch the extrusion. Steam, bubbles in the bead, or a rough fuzzy texture on the line = wet.
3. Stringing tower test: wet filament strings even at perfect retraction settings.
4. Snap test: bend a 10 cm piece of filament hard. Dry PLA breaks cleanly. Wet PLA bends rubbery and breaks with fibers.
5. Humidity reading: some Bambu / Polymaker spool boxes report internal humidity. Above 30% = drying time.

Drying methods

Dedicated filament dryers (best)

Purpose-built dryers hold accurate temperatures, often print directly from the dryer, and dehumidify with desiccant + heat.

• Sunlu S2 / S4: $50–$120, 70 °C max. Good for PLA/PETG/ABS.
• Polymaker PolyDryer: $60–$100, prints-from feature.
• PrintDry Pro: $150, 80 °C max, can dry two spools at once.
• eSun eBox Lite / Pro: $40–$100, basic but functional.
• Bambu AMS / Bambu Lab dryer: $120–$300, integrates with the AMS feeder.

Food dehydrator (best value)

A $40 food dehydrator (Excalibur, Cosori, Magic Mill) does the job perfectly for everything below 80 °C. Remove the racks, set the temperature, run overnight. Confirm with an external thermometer — cheap dehydrators run 5–10 °C off.

Oven (works but risky)

• Most home ovens won't go below 65 °C (170 °F). Useless for PLA.
• Even at the lowest setting, ovens often overshoot by 20 °C during the heat-up cycle.
• Use a separate oven thermometer to verify actual temperature.
• For PETG/ABS/Nylon: oven at 70 °C, door cracked open with a wooden spoon to allow moisture out.

Microwave (don't)

Tempting because it's fast, but microwaves heat water unevenly — you'll get hot spots that deform the spool while other spots stay damp. Plus, any aluminum spool core or labels arcs. Skip it.

Storage: keep dried filament dry

Drying for 6 hours is wasted if you leave the spool on a shelf afterwards. PETG and nylon can re-absorb to printable-wet within 24 hours in humid climates.

• Vacuum bags + indicator desiccant: cheapest. Blue silica gel turns pink when saturated.
• Sealed dry boxes (Bambu AMS, Polymaker PolyBox, IKEA SAMLA + grommets): keep filament under 15% RH while printing.
• Pelican / Sterilite latching boxes with desiccant inside.
• Reusable silica gel (orange or blue indicator) regenerates in the oven at 120 °C for 3 hours.
• Hygrometer inside the box — aim for <15% RH.

How long stays dry?

Approximate re-absorption time from "freshly dried" to "noticeably wet again" in a typical 45% RH room, unsealed:

Sealed in a vacuum bag with fresh desiccant, all of the above last 6+ months without re-drying.

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