It’s white. It looks fluffy and cold. It’s… flour and salt?

Early filmmakers resorted to some pretty weird substances to create fake winter wonderlands. Some of them were even toxic.

“During the early days of Hollywood, fake snow was commonly used in place of the real thing, and there weren’t any computerized effects that could make snow,” writes Ernie Smith for Atlas Obscura. One early substance used was cotton, he writes, until a fireman pointed out that it was a bad idea to cover a film set in a flammable material. But a number of other materials were used over time to make it look as if it was snowy, even on a hot summer’s day on set.

Take the beloved Christmas classic It’s A Wonderful Life, for example. It was shot in June and July 1946, writes Andrew Liszewski for Gizmodo. The fictional town of Bedford Falls, where the winsome drama was set, was covered in newly quiet fake snow made out of foamite (the material used in fire extinguishers) mixed with sugar, water and soap flakes. Some 6,000 gallons of the stuff were used on set, writes Ben Cosgrove for Time, and RKO Effects Department won an award for the new snow. “The artificial snow even clung convincingly to clothing and created picture-perfect footprints,” he writes.

For a period before that, according to Cosgrove, fake movie snow was “mostly made from cornflakes painted white.” Sometimes they were mixed with shaved gypsum. It was so noisy that any snowy scenes that had dialogue had to be re-dubbed after.

“A little disconcerting, though, are reports that asbestos was also used to dress up some of the sets,” he writes. The known cancer-causing substance asbestos was used on more than one set: the famous scene in The Wizard of Oz where Dorothy falls asleep in a field of poppies and wakes up in a snow storm used asbestos, writes Smith. And it wasn’t the only film set to use asbestos in the 1930s.

Over the years, filmmakers have used a number of other substances to create the illusion of snow: marble dust in Dr. Zhivago (1965), salt and flour in Charlie Chaplin’s The Gold Rush (1925) and plain old salt in 1978’s Superman. These days, CGI plays a large part, as well as environmentally friendlier products like Snowcel.

So when you settle down with holiday favorites this year, think about where the snow came from.