PVA (Polyvinyl Alcohol) is a water soluble filament that can be used as support material for cleaner prints. PVA will "melt" away after printing when placed in room-temperature to luke warm water. Not all materials will stick to PVA so make sure to understand how your models are set up when using it as support material. It is also recommended to keep PVA dry as it is hygroscopic and will retain moisture. We have found when using eSun PVA, we were able to successfully print with old PVA that was not dry however you hear a lot of crackling noises.
Ease of Use