HOW TO IDENTIFY WET FILAMENT

Wet filament is filament that has absorbed enough water from the air to disrupt printing. The water boils inside the nozzle, creating steam pockets that disrupt extrusion, weaken layers, and produce visible surface defects. The symptoms overlap with many other problems - stringing, layer separation, rough surfaces, weak parts - which is why drying is the most-overlooked fix in the troubleshooting community. Identifying wet filament before troubleshooting other settings saves hours. A 2-minute check eliminates the most common silent cause of bad prints.

Check for wet filament when: you're troubleshooting any print quality issue and don't yet know the cause; the symptoms appeared after the spool had been sitting out; you're working with PETG / TPU / nylon / PC (high-sensitivity filaments); or you've been chasing a setting fix without success. Skip the check when: the filament is fresh from a sealed bag with desiccant. Or you're on PLA in a dry climate and the spool is days-old.

Run through these six checks - any one positive means dry the spool: 1. Listen during printing. - Stand close to the hotend during the first few minutes. - Listen for sharp popping, crackling, or hissing sounds. Like a tiny popcorn popper. - Even occasional pops mean wet filament. Loud constant pops mean very wet. - This is the #1 most reliable indicator. 2. Look at recent print surface texture. - Wet filament leaves rough, pitted, bubbly surface texture - distinct from over-extrusion (uniform bumpiness) or under-extrusion (gaps). - Look at side walls in good light. Wet filament looks chewed-up. 3. Check for steam from the nozzle. - Light a flashlight from the side, look at the nozzle area during extrusion. - Wisps of steam or smoke = wet. - Use this in a dark environment for best visibility. 4. Snap test (filament off the spool). - Pull about 30 cm of filament off the spool. - Bend it back and forth in a tight U-bend. - Dry filament: bends without snapping until creased many times. - Wet filament: snaps cleanly with one bend, especially nylon / PC. PLA snap test is less reliable. 5. Inspect the spool itself. - Older filament that's been sitting out: the surface of the strand may look dull or hazy compared to fresh shiny filament. - Hairs, fuzz, or fibres along the strand: wet TPU or PETG specifically does this. 6. Check storage history. - How long has the spool been out of sealed storage? - PLA: weeks to months in normal humidity = potentially wet. - PETG: days to weeks = potentially wet. - TPU / nylon: hours to days = potentially wet. - If the answer is 'longer than the time guideline above for this filament', assume wet and dry.

Confusing wet filament with under-extrusion. Both can produce pitted surfaces, but wet filament also pops audibly and shows steam. Under-extrusion is silent. Confusing wet filament with over-temperature. Both can string, but over-temp stringing is consistent line by line. Wet filament stringing is irregular and accompanied by popping. Snap-testing PLA and concluding it's wet. PLA's snap behaviour doesn't change much with moisture. Use snap test for nylon, PC, and PETG primarily. Trusting 'sealed packaging' from the manufacturer. Some brands ship spools that absorbed moisture before packaging, especially budget brands. Always do the popping check on a fresh spool. Not testing after drying to confirm. Run a small test print after drying to verify the popping has stopped. Otherwise you don't know if drying worked.

If wet, see how-to-dry-filament for proper drying procedure. To prevent re-absorption: how-to-store-filament. For fix-side context on wet-filament symptoms: fix-wet-filament.