One of the most overlooked causes of 3D printing failure is damp filament. Most 3D printing thermoplastics are "hygroscopic," meaning they actively absorb moisture from the surrounding air. While some materials like PLA are relatively slow to absorb water, others like PETG, Nylon, and TPU can become "wet" enough to ruin a print within just a few hours of exposure to high humidity.
When damp filament is fed into a hot nozzle, the water trapped inside the plastic is instantly heated beyond its boiling point. This water turns into steam, expanding rapidly and creating internal pressure. This physical reaction causes several distinct symptoms: a "popping" or "crackling" sound as the filament exits the nozzle, excessive stringing and oozing, and a rough surface finish characterized by tiny pits or bubbles where the steam escaped the molten plastic.
Beyond surface defects, wet filament significantly compromises the structural integrity of the print. The steam bubbles create voids within the extruded lines, meaning the layers do not bond together as strongly as they should. In extreme cases, a part printed with wet Nylon can be snapped by hand, whereas the dry version would be nearly indestructible. This is a chemical change as well; in some materials, the presence of water at high temperatures causes a process called "hydrolysis," which permanently breaks the polymer chains and reduces the material's strength.
To solve this, you must dry the filament. A standard kitchen oven is often too inconsistent and can melt the entire spool, so a dedicated filament dryer or a food dehydrator is recommended. Drying times vary, but 4 to 12 hours at a specific temperature (usually 45°C for PLA and 65°C for PETG) will restore the material to its optimal state. Once dried, store your filament in airtight containers or vacuum-sealed bags with plenty of silica gel desiccant to prevent it from absorbing moisture again.