To make a certain piece, the designers first sew a simple mold from a coated textile—an idea that was crucial to their success, it turns out. Metal molds would have been too expensive. “Because polystyrene expands at 212 degrees, and you can wash clothes at that temperature, we thought to use fabric,” says Aparicio. “It’s so much cheaper to be able to sew your own mold, not to mention faster and easier to change. It’s more like drawing, in a way.” The mold gets packed completely full with granules.