The hiss at the nozzle has a diagnosis — and a table for the cure.
Print a spool that has sat open in a humid room and the printer announces the problem: a faint crackle and hiss as each section passes the nozzle, small bubbles in the lines, stringing where the surface used to be clean. The sound is water flashing to steam at the melt temperature. The drying guide carries the app's cure table; this is the why underneath it.
Two things, at two scales. At the nozzle, the absorbed water boils through the melt as vapor: the bubbles leave voids and rough walls, the extrusion turns inconsistent, and steam pushing sideways is where the stringing comes from. In the polymer itself, moisture plus heat is slower chemistry: polyesters (PLA and PETG both) soften their own chains — molecular weight drops, and the mechanical results in the print follow. A wet-print-dry-print-wet cycle costs the filament twice: once in the print's surface, and again in the material's strength.
The drying table reads straight off the app's timers — the same values its drying alarms ring for:
| material | temp | hours |
|---|---|---|
| PLA | 50 °C | 8 h |
| PETG | 65 °C | 8 h |
| ABS | 80 °C | 8 h |
| TPU (95A) | 70 °C | 8 h |
| PC | 80 °C | 8 h |
| Nylon (PA) | 80 °C (estimate) | 8 h |
The guide's honest footnote carries across: the nylon row is the app's own estimate — nylons vary widely, so the spool's label wins. And the exclusion is worth memorizing before anything else: PCL pen filament is not oven-dried, because it softens around 60 °C — a drying box would cook it before it dried it.
The alarm's notification text says the whole rule: "bag it with desiccant while it's warm, or print it now." A spool that dries and then cools in open air starts drinking the room's humidity again immediately — the warm bag with desiccant inside is what keeps the 8 hours from being rented. Wet it, dry it at the table's number, bag it warm. The print stops hissing the moment the water does.
Bag it warm. — the bench crew