Popping sounds while printing, bubbles on the surface, stringing and brittle, poorly bonded layers — before you start tweaking temperatures, check the simplest cause: moist filament. 3D-printing plastics are hygroscopic, meaning they absorb water from the air — some slowly, others surprisingly fast.
Which filaments absorb moisture fastest?
| Material | Moisture sensitivity | Symptoms |
|---|---|---|
| PLA (also Silk, Rainbow) | moderate | brittle prints, dull surface |
| PETG | elevated | stringing, bubbles, popping |
| TPU (flexible) | high | foamy prints, poor layer adhesion |
| PA (nylon) | very high — can absorb moisture within hours | a drastic drop in strength |
| CF composites (PLA/CF) | elevated | nozzle clogging, uneven extrusion |
Storage — three levels
- Minimum: after printing, the filament goes back into a zip-lock bag with a desiccant (silica gel). Bags and gel cost pennies — the best effect-to-price ratio there is.
- Standard: an airtight container (a box with a gasket) with a handful of silica gel and an inexpensive hygrometer. Target: below 20% RH inside the box.
- Pro: a dry box with a feed-through — the filament prints straight from the container. Mandatory for PA and TPU if you print them regularly.
How to dry moist filament?
Approximate drying parameters (a filament dryer, or a fan oven with an accurate thermometer):
- PLA: 45–50 °C, 4–6 h
- PETG: 60–65 °C, 4–6 h
- TPU: 50–55 °C, 6–8 h
- PA (nylon): 65–80 °C, 8–12 h — ideally dry it before EVERY print
- CF composites: 55–65 °C, 6–8 h (according to the base material)
Watch out for two things: don’t exceed the softening temperature (PLA above ~55 °C can fuse together on the spool), and let the filament cool inside a closed container rather than in humid air.
How do you know it’s moisture and not your settings?
The simplest test: listen to your printer. Moist filament crackles and hisses in the nozzle (that’s water evaporating). A second signal: compare a print from the same spool freshly opened and after two weeks on the desk — the difference can be striking, especially with PETG.
A starting tip: Porima filaments arrive vacuum-packed with a desiccant — don’t open spare spools until you need them. You’ll find printing temperature ranges for all materials in our temperature chart, and the full range in the Porima catalogue.