Capra used a new form of snow for It's a Wonderful Life.
Snow is a must for family Christmas films, but how do you film a cold scene in the middle of say … July? The answer: simple movie magic.
In the early days of Hollywood, movie studios often used bleached cornflakes as a substitute for snow (or even cotton and asbestos), requiring redubbing for close-up wintry scenes. It also didn't allow for footprints, tire tracks, and the like to appear in the snow, which would help sell the scene.
That wouldn't fly for director Frank Capra's 1946 melancholy yuletide classic It's a Wonderful Life. "Capra wanted to be able to shoot live dialogue in close-ups while snow was falling and he also knew he needed a lot of snow in general," says Jeremy Arnold, author of Christmas in the Movies.
Capra recruited RKO special-effects department head Russell Shearman to devise a silent solution to fall and blanket his enormous 4-acre set. The result: a mixture of Foamite (found in fire extinguishers), soap, sugar, and water that could be shot out of canisters at high pressure and gently wafted over the set with a silent fan.