Many filaments absorb moisture from the air – some within a few hours. Wet material boils in the nozzle: you hear crackling, see steam, and the print has strings, bubbles and is brittle. No calibration will fix that – dry it first.
Filament manufacturer's guidance comes first. Every manufacturer has its own formulations and publishes its own parameters – nozzle, bed and chamber temperature, drying, cooling. Even the same material (e.g. PETG) from two brands may need different settings. Treat the values in this guide as a starting point: check the technical data sheet (TDS) and the spool label first, and if something is missing, ask the filament manufacturer for guidance.
How to recognise wet filament
- crackling and hissing during extrusion, sometimes visible steam,
- a lot of stringing despite correct retraction,
- a matt, rough or porous surface,
- brittle prints, and filament that snaps when bent (especially PLA and PA).
Indicative drying parameters
Always check the manufacturer’s recommendations – these values are a safe starting point. The temperature must stay below the material’s softening point, otherwise the filament fuses on the spool.
| Material | Temperature | Time | Moisture sensitivity |
|---|---|---|---|
| PLA | 45–55 °C | 4–6 h | low–medium |
| PETG | 60–65 °C | 4–6 h | medium |
| ABS / ASA | 70–80 °C | 4–6 h | low–medium |
| TPU | 50–55 °C | 4–8 h | high |
| PA (nylon), PA-CF | 70–90 °C | 8–12 h | very high |
| PC | 70–80 °C | 6–8 h | high |
What to dry with
- Filament dryer – the simplest and safest option, often letting you print straight from the dryer.
- Food dehydrator with temperature control – works well for PLA and PETG.
- Oven – only if it holds a low temperature steadily; many ovens swing a lot and can melt the spool.
- The printer’s heated bed under a box – an emergency option, not very effective.
How to store it
After drying, keep the spool in an airtight container or bag with a desiccant (silica gel with an indicator). Very hygroscopic materials (PA, PC, TPU) are best printed straight from a dryer or a dry box.
How much moisture is too much?
Filament starts absorbing water the moment you open the bag. PLA survives weeks on an open shelf, PETG a few days, while nylon (PA) and TPU can soak up moisture overnight. With workshop humidity above 50% you see the difference quickly: more stringing, a matt and rough surface, weaker layer bonding. A cheap hygrometer in the filament cabinet tells you more than guessing.
Large prints are more sensitive
On a large-format printer one spool often runs for 20–40 hours. If it sits on an open holder all that time, it is wetter at the end of the print than at the start – and the top layers come out worse than the bottom ones. For long prints in PETG, PA, PC and composites, print straight from a dry box or a dryer with a filament outlet.
Most common mistakes
- Too high a temperature – PLA at 60 °C can fuse the windings on the spool. Stay at the lower limit for the material.
- Drying without ventilation – the water needs somewhere to go. A closed container without air exchange dries very slowly.
- Drying and back on the shelf – after a few days the effect is gone. Put the dried spool straight into an airtight box with a desiccant.
- Cardboard spools in the oven – cardboard can warp; a filament dryer is better.
Back to the new filament checklist.
