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.
If you can hear hissing/popping from the nozzle, or your prints have bubbles, stringing, or rough surfaces — dry the filament. PLA: 45 °C / 6 hours. PETG: 65 °C / 6 hours. ABS: 70 °C / 4 hours. TPU: 55 °C / 8 hours. Nylon: 80 °C / 12–16 hours. Store dried filament in an airtight container with fresh desiccant.
When wet filament hits the melt zone (200–280 °C), absorbed water flashes to steam inside the molten plastic. The steam:
Drying restores the polymer's print performance — but it can't reverse hydrolysis, so badly degraded nylon may never print like new again.
Sources cross-checked against PrintDry, Polymaker, Bambu Lab, and individual filament manufacturer datasheets. Use the longer end of the range for fully-saturated filament.
Purpose-built dryers hold accurate temperatures, often print directly from the dryer, and dehumidify with desiccant + heat.
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.
It'll soften the spool into a fused puck. Use a dehydrator or dedicated dryer.
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.
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.
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.