Filament Moisture: Signs, Drying and Proper Storage
Moisture is filament's sneakiest problem: the part comes out bad and the slicer or printer gets the blame. Moisture causes weak layers, stringing, bubbles and failed prints, which makes it a direct cost.
Signs of wet filament
- Crackling or popping sounds while printing, or steam from the nozzle.
- Heavy stringing and dripping from the nozzle tip.
- A rough, dull or bubbly surface.
- Poor layer adhesion and parts that snap easily.
- A print that used to look good suddenly going bad with the same settings.
Which materials absorb how much?
All of them absorb moisture (they are hygroscopic) but at different rates. A rough order from least to most:
- ABS, ASA (relatively low)
- PLA, PETG (medium; absorb over time)
- TPU (high)
- Nylon (PA) and PVA (very high; absorb quickly)
Drying: temperature and time
Drying temperature must stay below the material's softening point. These are typical ranges; always check the manufacturer's label:
| Material | Temperature | Time |
|---|---|---|
| PLA | 45–55 °C | 4–8 hours |
| PETG | 60–65 °C | 4–8 hours |
| ABS / ASA | 70–80 °C | 4–6 hours |
| TPU | 50–70 °C | 6–8 hours |
| Nylon (PA) | 70–80 °C | 8–12 hours |
Keep PLA's temperature low; do not let the spool deform. After drying, put the filament straight into a closed box, or one that keeps drying while you print; in open air it absorbs moisture again.
What drying costs
Drying is usually cheap. A 70 W filament dryer running 6 hours uses 0.07 kW × 6 hours = 0.42 kWh; at $0.15 per kWh that is about 6 cents. A single ruined print costs far more. We calculate the effect of failed prints on cost in the failed prints guide.
Proper storage
- Sealed box + desiccant: an airtight box with silica gel or similar. Renew the desiccant regularly.
- Vacuum bags: cheap and effective for spools you are not using.
- Dry box for printing: especially useful for nylon, PVA and TPU, which need to stay dry during the whole print.
- Humidity meter: put a small hygrometer inside and watch the numbers; do not manage it by guesswork.
- New spools: keep the factory packaging closed until you need it.
The cost view
Every print ruined by moisture is lost filament and electricity. If you keep having trouble, remove the root cause (moisture) instead of raising your failure margin; a dryer and desiccant pay for themselves within a few months.
Frequently asked questions
Does PLA absorb moisture, and should I dry it?
Yes, PLA absorbs moisture over time, though not as fast as nylon, PVA or TPU. If you see crackling, stringing or a rough surface, drying PLA at a low temperature often fixes it.
Can I dry filament in a kitchen oven?
We do not recommend it. Home ovens are usually imprecise at low temperatures; the heat can overshoot and deform the spool or PLA. A filament dryer, or a dryer that holds a steady low temperature, is safer.
How do I measure humidity?
Put a small hygrometer in your storage box. As a rule of thumb, keeping relative humidity around or below about 20% for nylon, PVA and TPU, and below 30–40% for PLA and PETG, gives good results. Follow the manufacturer's advice if there is one.
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