Here's the cool thing that happens when you pour molten aluminum inside polymer water balls

The Backyard Scientist filled a tank to the brim with water balls, which are little polymer beads that expand to slimy squishy balls when soaked in water, and then poured in molten aluminum to create some wild designs. It's cool because with all the different ways the molten aluminum can move within a vat filled with balls, each pour results in a totally different design.