Why you should dry filament before printing
Filament absorbs moisture from the air. In the hot nozzle that water turns to steam and ruins the print: bubbles, strings, rough surfaces and weak layers.
What happens when filament is wet
Bambu Lab sums it up: moisture leads to stringing and parts that break easily [1]. In practice the signs are [2]:
- popping or hissing at the nozzle, sometimes with visible steam;
- bubbles or a dull, rough surface on the extruded line;
- stringing that retraction tuning does not fix;
- weak layers that snap easily;
- gaps and thin walls that look like under-extrusion.
Over time water can also damage the material: pure PLA can lose strength through hydrolysis [3], and nylon absorbs a lot of moisture, with stiffness dropping to as little as a third of the dry value in some cases [3].
Which materials suffer most
- Nylon (PA): the most sensitive; almost always needs drying.
- TPU and PETG: show strings and rough surfaces very quickly.
- PLA, ABS, ASA: react more slowly, but after weeks in open air or in a humid climate the defects appear.
When drying is really needed
- A new, sealed spool with desiccant is usually fine straight away.
- The spool has been open for days or weeks, especially in summer or in humid areas.
- You see the signs listed above.
- You print nylon or TPU: always dry first and, if you can, print from a dry box.
Indicative drying values
| Filament | Temperature | Time |
|---|---|---|
| PLA | 40–50 °C (never above ~55 °C) | 4–6 hours |
| PETG | 60–70 °C | 4–6 hours (up to 8) |
| ABS / ASA | 65–80 °C | 4–8 hours |
| TPU | 55–70 °C | 6–12 hours |
| Nylon (PA6, PA12) | 70–90 °C | 8–12 hours |
Values from PrintPal [2]. Bambu Lab lists higher temperatures (for example 65–75 °C for PLA, 12 hours) because those are heatbed temperatures with the drying cover, not filament temperatures [1]. If you use a dedicated dryer, follow the table. For the practical steps see how to dry filament.
How to store it afterwards
- In a sealed box or vacuum bag with desiccant.
- Relative humidity below 20%, with a hygrometer inside the box [2].
- Regenerate or replace silica gel according to its label [2].
Sources last checked: November 2026. Values are indicative: always check your spool manufacturer’s data sheet.