I have been storing my filament in air-tight cereal containers along with desiccant and a hygrometer (after drying if applicable). All has been fairly good, with a few exceptions of some spools of PETG being wetter than indicated by the hygrometer.
This is where I have this conundrum: should filament be stored without desiccant so that the representative RH (Relative Humidity) of the filament is indicated by the hygrometer; or does storing it with desiccant, which results in the hygrometer only indicating air RH, and not filament RH, still win out because of the long-term tendency of the desiccant to slowly dry the filament?
No, you should keep it with the desiccant when storing, that way any air that get in there should have its moisture mostly sucked up by the desiccant.
This is the only reason to use it, it won’t pull moisture out of the filament, but hopefully it will pull it out of the air before it can get into the filament.
The hygrometer is to tell you when the desiccant is spent.
Weighing before and while drying is the ultimate solution, when weight stops being lost after a few hours of drying it is done.
But I attempt to short cut it, I load up the filament, manually set hotend to 250C, manually extrude a good bit out of the nozzle and note that it is coming straight out and down. Finally, quickly clip off the excess filament with tweezers, now does the filament continue to creep out of the hotend? That’s moist filament.
Ah yes, I totally forgot about that. Thanks for the reminder! I need to set up a process/checklist to run through when drying, storing, and printing filament.