How to store filament

Most consumer filaments — PLA, PETG, ABS, nylon, TPU — are hygroscopic. They absorb water from the air. Wet filament prints poorly: bubbling, stringing, weak layer adhesion, sometimes audible popping at the nozzle.

How long before it goes bad

Roughly, in normal indoor humidity (40–60%):

• PLA: noticeable after about a month. Severe after 3.
• PETG: noticeable after about a week. Severe after a month.
• Nylon: noticeable within hours. This is not an exaggeration.
• TPU: noticeable within a few days.
• ABS / ASA: more forgiving but not immune.

The cheap option

Buy a large airtight container (a 5-gallon bucket with a gamma-seal lid, or a cereal storage box from a kitchen-supply store) and toss in a few silica gel desiccant packs. Replace the packs every couple of months or buy a small electric "regenerable" dehumidifier puck.

For a multi-spool setup, a vacuum-sealed bag with a desiccant pack works almost as well and takes no shelf space.

The "actually invest in this" option

A filament dry box that holds your spool while you print is the gold standard. They run $30–80 for a single-spool box that you tape to the side of your printer.

Above that price range, "Polybox"-style multi-spool dry cabinets exist but are overkill unless you're printing professionally.

How to dry a wet spool

1. Put the spool in an oven at the lowest setting (PLA: ~40°C, PETG: ~65°C, nylon: ~80°C) for 4–6 hours. Do not exceed the glass transition temperature — you'll fuse the spool into a brick.
2. Alternatively, run it through a dedicated filament dryer (works like a food dehydrator) for the same time at the same temps.
3. Store it dry immediately after. Drying is reversible.

Signs your filament is wet

• Hissing or crackling at the nozzle during printing.
• Visible steam from the nozzle (yes, really).
• Layer adhesion drops noticeably between identical files printed a month apart.
• Print surface looks rough, "wet", or pock-marked.