Why moisture ruins prints — and how to store and dry filament properly
Filament is hygroscopic: it absorbs water straight out of the air. A spool left open for a few weeks in a humid room can pick up enough moisture to noticeably hurt print quality. The good news is that storing filament well is cheap and easy, and even a wet spool can usually be revived by drying.
Moisture in filament turns to steam at the nozzle, which causes tell-tale symptoms: a faint crackling or popping sound while printing, tiny bubbles or a rough "blistered" surface, weak and brittle layers, excessive stringing, and inconsistent extrusion. PETG, nylon and TPU absorb water fastest; PLA is more forgiving but not immune. If a once-reliable spool suddenly prints badly, suspect moisture before anything else.
The goal is to keep humidity low. Store spools in airtight containers — sealable plastic bins or vacuum bags work great — with desiccant inside. Rechargeable silica gel packs are ideal because you can dry them out and reuse them; many turn from orange to green (or blue to pink) when saturated, so they double as a humidity warning. Aim to keep the enclosed humidity under about 20% RH; a cheap hygrometer in the box tells you at a glance.
If a spool has already absorbed water, dry it before printing. A dedicated filament dryer is easiest, but a food dehydrator or even an oven on its lowest setting works if you watch the temperature. Use roughly 45–55 C for PLA, 60–65 C for PETG, and 70–80 C for nylon, for around 4–6 hours. Stay well below the material's glass-transition temperature so the spool doesn't soften or fuse — and never microwave filament.
It helps to track which spools have been dried and when you opened them, so you always reach for a known-good roll. Logging the dry status and open date per spool means no more guessing whether that half-used PETG is still good.
Track spool dry status in PrintLog →