We've all seen fake snow that can be sprayed on windows, trees, etc., but did you know there's also fake ice crystals? MTFX demonstrates above.
I learned about it on a shoot about 15 years ago. It works on any window, but the prop person who showed me how to use it said it works best on a freshly-cleaned dry window where the glass has been gently warmed up with a hair dryer.
The most popular brand is Santa Ice Crystal Spray, which makes more traditional frost and snow as well.
Image: YouTube / MTFXlimited