How Fake Snow Works
Last Christmas, I received a curious gift: a tiny bag of white crystals labeled Fake Snow. "Just add water," it said. So I did. And the crazy stuff puffed up unbelievably, forming a white-ish snow-like substance. Even weirder, the bag indicated that the snow could be dried out and reused (!) -- I didn't try that part.
So what is fake snow? Apparently the powder I had was primarily sodium polyacrylate, a polymer that can absorb 200-300x its own mass in water. This polymer also shows up in diapers and maxi-pads (thank you, science) and also in gardens, where it's used to hang onto water and release it over time. So indeed, if you take a batch of sodium polyacrylate, add water, then let it dry out, you can use it again. It's even "non-toxic" (though the packet, and various web resources I consulted, suggested that eating it would be a really bad idea due to its affinity for bonding with any nearby water). Apparently it should also not be poured down drains, for obvious reasons.
This video shows closeups of how sodium polyacrylate behaves when water is added. It's astounding how much water a tiny bit of this stuff can suck up. Enjoy:
And here's a slightly off-kilter ad for "Snow in Seconds™," showing how quickly the sodium polyacrylate absorbs water and puffs up, delighting kids and nerds alike. "It's even used in movies!" Note that the ad mentions how the snow "feels cold" -- this is because the substance ends up being primarily water, so handling it is like putting your hands in blobs of water. (You can also put it in a refrigerator to make it colder -- again, it's mainly water so it has similar behavior.) It takes a few days to dry out, and can be rehydrated when that occurs.
And here's a very short video showing water being added directly to a beaker of this stuff. It really is neat!
There are lots of fake snows online, though I couldn't find the sketchy dollar-store brand I used.
Have You Used Fake Snow?
I'm sure we have some fake snow experts in the audience. Can you share more about this substance? Do you save your fake snow and reuse it year after year? I'm genuinely curious how people interact with this stuff -- as I plan to turn my house into a Fake Snow Fortress this winter. (Watch out for wampas.)