How to Dry and Store Filament (and How to Tell It's Wet)
Contents
If you hear popping or hissing from the nozzle during a print, the filament has most likely absorbed moisture. Most filaments soak up water from the air. The water heats up in the nozzle and turns to steam, the plastic foams, the surface roughens and stringing increases. Drying the filament for a few hours at the right temperature usually solves the problem completely, and storing it properly keeps it from coming back.
Signs of wet filament
- Popping, cracking or hissing sounds during printing.
- Bubbles and steam in the plastic coming out of the nozzle.
- Heavy stringing that does not go away despite retraction tuning.
- Rough, matte or bubbly surfaces.
- Weak layer bonding and brittle parts.
- PLA that snaps easily as you unwind it from the spool (this is not always from moisture; it can be aging).
These signs can be confused with other problems. To be sure, dry the filament, print the same part again and compare.
How much moisture does each filament absorb?
| Filament | Moisture sensitivity | Drying temperature (approx.) | Time (approx.) |
|---|---|---|---|
| PLA | Low to medium | 45–50 °C | 4–6 hours |
| PETG | Medium to high | 60–65 °C | 4–6 hours |
| ABS / ASA | Medium | 65–80 °C | 4–6 hours |
| TPU | High | 45–55 °C | 4–8 hours |
| Nylon (PA) | Very high | 70–80 °C | 8–12 hours |
| PC | High | 70–80 °C | 6–8 hours |
These values are a general guide. The drying temperature must be below the filament's softening temperature, otherwise the filament sticks together on the spool. Always put the manufacturer's recommendation first. Plastic spools can also warp at high temperatures.
Drying methods
Filament dryer
Dryers designed for filament hold a set temperature, and some also keep the filament dry while printing. This is the safest and most practical method.
Food dehydrator
Models with temperature control work well for drying filament. The trays can be removed or a ring added so the spool fits.
Oven
Possible but risky:
- Household ovens are usually inaccurate at low temperatures and can be off by 10–20 °C. Check with a separate thermometer.
- If the oven's heating element radiates directly onto the spool, the filament melts.
- Heating plastic in a kitchen oven can release unwanted odors and emissions, especially with materials like ABS.
Because of these risks, use the oven only with care and control; a separate dryer is always better.
Heated bed
Some people put the spool on the printer's bed and cover it with a box. It can work for PLA, which needs a low temperature, but it is inefficient and the heat distribution is uneven.
Proper storage
Dried filament can absorb moisture again within a few days. Storage conditions matter as much as drying.
- Airtight box: Use sealed plastic storage boxes or vacuum bags.
- Silica gel: Put moisture-absorbing silica gel packs in the box. Types that change color show when they are saturated. You can reuse saturated silica by drying it at the temperature the manufacturer recommends.
- Hygrometer: Put a cheap digital hygrometer in the box. The aim is to keep the internal humidity below 20–30%.
- During printing: For sensitive materials such as PETG, TPU and nylon, feed from a dry box on long prints.
- Dust: Dust also leads to a clogged nozzle. Boxes protect filament from dust too.
Can a new spool also be wet?
Yes. Filaments are usually packed with a vacuum bag and silica gel, but they may have absorbed moisture during production or storage. It is a good habit to dry a new spool before use, especially with nylon, TPU and PETG.
When drying does not fix it
- Brittle PLA: PLA that has sat in a damp, warm place for a long time can degrade chemically. Drying may not fully cure the brittleness.
- Bubbles continue: The temperature may be too high, or the problem may come from something other than moisture.
- Stringing continues: Also check the retraction settings and the temperature.
Do I really need to dry PLA?
PLA stored in a dry place usually does not need drying. But in a humid climate, or if it has been left out for a long time, drying clearly reduces stringing and surface problems.
Does drying for longer do harm?
A few extra hours at the right temperature usually does no harm. But raising the temperature can soften the filament and make it stick together on the spool.