Their biggest departure from typical styrofoam manufacturing, though, was what happens here, inside their homemade oven. To make a long story short, industrial polystyrene is pre-expanded, loaded into molds, and then quickly puffed up into its super-expanded, lightweight form. Silo’s styrofoam is heated only once, but much more slowly, and is puffed up only halfway, so it’s much more dense and durable. The pressure of the granule-packed fabric lends enough pressure to ensure the half-baked granules still stick together.