In short
- Damp filament pops in the nozzle, strings and gives rough, weaker prints.
- PLA: 45–50 °C for 4–6 h. PETG: 65 °C. PA6-CF nylon: 80 °C for up to 12 h.
- The drying temperature must be lower than the one at which the material softens.
- Keep dry spools in an airtight box with desiccant, below 20% humidity.
Where the moisture comes from
Most filaments absorb water vapour from the air. PLA does it slowly, over weeks, and nylon within hours. In a hot nozzle that water boils and ruins the print.
How to spot damp filament
- Popping and hissing from the nozzle
- Strings between parts
- Bubbles and a rough surface
- Weaker layer bonding
A simple test: push a piece of filament through the nozzle into the air. If it pops, hisses or comes out with bubbles, it needs drying.
What temperature and how long
Pick a material to see its drying temperature and time, and how quickly it absorbs moisture. The black line on the thermometer shows the temperature at which the material softens. The dryer has to stay below it, or the filament will stick together on the spool.
After a few weeks out of the box it's worth drying.
The ranges come from filament manufacturers' data sheets, so check the label on your spool as well. The dryer has to stay below the temperature at which the material softens.
What to dry it in
A filament dryer is the most convenient. It holds a steady temperature, and many models let you print straight from inside.
A food dehydrator with temperature control also works well, as long as the spool fits inside.
An oven is only suitable with a separate thermometer. Its temperature can swing by more than ten degrees, which is enough to warp a plastic spool. A radiator or a hair dryer won't dry the filament deep inside the spool.
How to store spools
Dried filament stays dry as long as it has nowhere to pick up moisture.
Silica gel beads change colour once they're saturated. Then they need drying or replacing.
- Keep spools in an airtight container or a zip bag with desiccant (silica gel).
- Put a hygrometer in the box. It's cheap and shows when to replace the desiccant.
- Keep nylon and TPU in a dry box while printing too. The filament can feed through a hole straight to the printer.
Technical materials such as PA6-CF need a dryer, a hardened nozzle and a closed chamber. If you need just one such part, it usually works out cheaper to order it. Print settings for every material are on the materials pages.