Capra—who trained as an engineer—and special effects supervisor Russell Shearmanengineered a new type of artificial snow for the film. At the time, painted cornflakes were the most common form of fake snow, but they posed a bit of an audio problem for Capra. So he and Shearman opted to mix foamite (the stuff you find in fire extinguishers) with sugar and water to create a less noisy option.