So I was checking out some cool videos on youtube of helium in superfluid state and I have a question about it. How exactly does this superfluid have both zero and non-zero viscosity at the same time? The evidence seems pretty clear that it exhibits zero viscosity since it forms a Rollin film and it can appear non-zero because if you spin a drum inside it the fluid begins to turn. It is also known that it is not a mix of two types of fluid but rather one fluid that exhibits both properties at the same time (100% of the fluid will drain through a Rollin film not just a zero viscosity portion of it). So how is this possible? Does it have anything to do with QM? Is it like a macroscopic superposition of both zero and non-zero viscosity fluid?