Hygroscopicity is an undesirable effect in filaments for 3D printing. Plastic polymers consist of chains of molecules joined together. The absorbed water molecules destroy these chains, destroying the plastic and causing many problems when printing.
Don’t worry, the “wet” filament spools can be quickly dried, and proper storage can prevent future accidents.
Below, we look at how to recognize a wet filament, how to dry it, and finally how to store it correctly.
Dried filament Moist filament
Comparison of dry and wet filament print
The easiest way is to extrude some filament and watch it come out of the nozzle. If you see any bubbles, hear a hissing/crackling/cracking, or see steam coming out of a filament, it means it is wet and needs to be dried.
Such filament should be subjected to the drying process as soon as possible to preserve strength and print quality.
Remember, there are cases of particularly hygroscopic materials, such as PA, PETG, PVA, or TPU, symptoms may appear after one night of improper storage.
Probably the easiest and most common way to dry a filament is to throw it into the oven/stove. Just set the temperature just below the glass transition temperature of the plastic and leave the spool for 4-6 hours for the moisture to evaporate. The longer we carry out this process, the drier our material will be.
Approximate drying temperatures below for four basic filaments:
• PLA: ~ 40-45 °C
• ABS: ~ 80 °C
• Nylon: ~ 80 °C
• PET-G ~ 80 °C
The second way is to use a food dryer. Perfect for drying filaments, especially if we do not have an oven/stove. Initially designed for drying fruit, they work at lower temperatures than ovens and, therefore, can easier adapt to work with a filament spool.
Now that your filament is dry, you’ll want to keep it in that condition for as long as possible. To do this, store dry spools in a controlled humidity environment. It can be anywhere – from a sealed box with moisture absorbers to dedicated commercial solutions. Usually, the first way is enough, but use the one that best suits your needs.
REMEMBER: proper storage is not able to dry the filament – it can only protect against moisture. If the filament gets wet again, it must be dried.