Drying filament: moisture, process and storage

How wet filament shows itself

• Audible popping or hissing at the nozzle — steam escaping
• Fuzzy, stringy surfaces on settings that used to print clean
• Brittle prints that snap along layers at half their usual strength
• Bubbles or pockmarks on what should be smooth walls

Which materials care

PLA tolerates humidity for a while but degrades over weeks exposed. PETG and TPU absorb faster and show it sooner. Nylon and PA6-CF are the extreme case — hours in open air are enough to matter, and they should live in a dry box even while printing.

Drying profiles that work

A purpose-built filament dryer is the reliable tool; a convection oven works if it holds temperature honestly (many overshoot, and 10°C too hot fuses a spool).

• PLA / PLA+ — 45–50°C for 4–6 hours
• PETG — 55°C for 4–6 hours
• TPU — 55°C for 4–5 hours
• ASA / ABS — 60°C for 4 hours
• Nylon / PA6-CF — 70°C for 8–12 hours, then straight into a dry box

Storage that keeps them dry

Drying is wasted without storage. Airtight boxes or zip bags with desiccant hold spools at 10–20% RH; a cheap hygrometer in the box tells you when silica needs recharging (30 minutes in a pan on low heat brings the color back). Print nylon from the dry box itself, feeding through a small hole — in coastal humidity it reabsorbs faster than a long print finishes.