Casting molten aluminum with seashells

In this video, Seth Robinson casts molten aluminum with Marlin Spike seashells, resulting in a strange and beautiful paperweight: "we're used to seeing the outside of seashells, but never the inside". The process is more involved that this description suggests: the shells are carefully encased in petrobond sand and a clamped box before the metal is even melted. And then follow hours removing and smoothing off the pouring channel and buffing the cast.