Learn · updated 2026-09-24
Does filament really need drying?
Short answer
PLA mostly tolerates humidity; PETG, nylon and TPU do not, and nylon is the extreme case. Wet filament prints with popping, stringing and weak layers. A few multi-material units dry spools while feeding them, which matters most on long prints.
What moisture does
Several common filaments are hygroscopic — they absorb water from the air. When that filament reaches the melt zone the water flashes to steam, which produces audible popping, a rough surface, heavy stringing and noticeably weaker layer bonding. The material has not gone off permanently; drying it restores it. The effect ranges from negligible on PLA in a dry room to severe on nylon, which can absorb enough moisture to print badly within hours of being unsealed.
The order of fussiness
Roughly, from least to most affected: PLA, PETG, ABS and ASA, TPU, PA (nylon) and PC. Carbon- and glass-filled versions of any of these tend to be worse than the unfilled base, because the filler gives water more surface to cling to. If you only print PLA in a heated house, this is a non-issue. If you want nylon, a dryer is not optional equipment.
Where the printer comes into it
This becomes a purchasing question with multi-material units, because a four-spool changer keeps three spools sitting exposed for the whole print. On a twenty-hour multi-colour print in a humid room, that is long enough to matter. Some changers in this catalogue actively heat and dry the spools they hold; others are unheated boxes. That difference does not show up in the headline specification but is one of the more consequential distinctions between them.
Doing it yourself
A dedicated filament dryer is the convenient answer; a food dehydrator with the shelves removed is the common cheaper one. Vacuum bags with desiccant keep dried spools dry. What does not work is leaving spools on an open shelf in a garage and hoping — which is, in practice, how most filament that prints badly got that way.