# How did this Halloween decoration work? **URL:** \ **Category:** Factual Questions\ **Created:** [December 22, 2003, 8:55pm UTC](https://boards.straightdope.com/t/how-did-this-halloween-decoration-work/220519 "2003-12-22T20:55:04Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Eleusis](https://avatars.discourse-cdn.com/v4/letter/e/f4b2a3/32.png) [@Eleusis](https://boards.straightdope.com/u/Eleusis)\ **Post date:** [December 22, 2003, 8:55pm UTC](https://boards.straightdope.com/t/how-did-this-halloween-decoration-work/220519/1 "2003-12-22T20:55:04Z")
I noticed it at my mother’s house over halloween, and am just now getting around to asking about this. It’s a plastic witch with a cauldron. You fill the cauldron with regular tap water and plug it in. You can hear a little motor which circulates the water. In minutes, dense heavy fog covers the water in the cauldron and spills over the sides. The fog is identical in appearence to fog produced by dry ice. There is no place to add anything else besides water, unlike a stage smoke machine. Any ideas? ---
**Author:** ![Eleusis](https://avatars.discourse-cdn.com/v4/letter/e/f4b2a3/32.png) [@Eleusis](https://boards.straightdope.com/u/Eleusis)\ **Post date:** [December 22, 2003, 8:57pm UTC](https://boards.straightdope.com/t/how-did-this-halloween-decoration-work/220519/2 "2003-12-22T20:57:43Z")
[Here is a pic of a similar one](http://www.johnsonsmith.com/website/store/product_detail.asp?UID=2003122215591722&item_no=25904) ---
**Author:** ![stuyguy](https://avatars.discourse-cdn.com/v4/letter/s/ec9cab/32.png) [@stuyguy](https://boards.straightdope.com/u/stuyguy)\ **Post date:** [December 22, 2003, 9:04pm UTC](https://boards.straightdope.com/t/how-did-this-halloween-decoration-work/220519/3 "2003-12-22T21:04:08Z")
My guess: It probably works like a humidifier. The how-stuff-works website could probably supply the particulars. ---
**Author:** ![stuyguy](https://avatars.discourse-cdn.com/v4/letter/s/ec9cab/32.png) [@stuyguy](https://boards.straightdope.com/u/stuyguy)\ **Post date:** [December 22, 2003, 9:48pm UTC](https://boards.straightdope.com/t/how-did-this-halloween-decoration-work/220519/4 "2003-12-22T21:48:04Z")
Here, check out the ultrasonic type humidifier: > **[How Humidifiers Work](https://home.howstuffworks.com/humidifier.htm#pt4)** > > Is the air feeling a little too dry in your home? A humidifier can help make things more comfortable -- and even save a little wear and tear on your house. You might be surprised how big a difference a little water can make. Again, just my guess. BTW, that’s one wacky site you linked to Eliusis. Dog poop Xmas tree ornaments? Umm… I’ll pass thanks. ---
**Author:** ![chorpler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chorpler/32/2888_2.png) [@chorpler](https://boards.straightdope.com/u/chorpler)\ **Post date:** [December 23, 2003, 12:33am UTC](https://boards.straightdope.com/t/how-did-this-halloween-decoration-work/220519/5 "2003-12-23T00:33:23Z")
I remember an ultrasonic humidifier that we used to have when I was a kid, that produced similar fog when opened up. It had a stream of water rising up out of the middle of the reservoir of water … and when you put your finger in that stream of water, it stung like crazy. Also … heh heh … this was really stupid … when I put my glasses in the stream so that the stream of water hit the front of the lens, after a few seconds the stream of water would rise straight through the lens and continue to its ordinary height. I called my brother and sisters and parents in to see how cool that was, and they speculated that the stream was somehow continuing around the side of the glasses and pooling on the top of the lens, and that the ultrasonic beam was then pushing the pool of water up somehow. As it turned out, of course, the water beam was melting right through the lenses – which we had forgotten were **plastic** – and my glasses were full of warped circular blobs. Not only did I have to get new lenses, I had to endure the mirthful laughter of the optometrist and his entire staff as my mom explained what had happened. Grrr… ---
**Author:** ![raygirvan](https://avatars.discourse-cdn.com/v4/letter/r/ac91a4/32.png) [@raygirvan](https://boards.straightdope.com/u/raygirvan)\ **Post date:** [December 23, 2003, 3:37am UTC](https://boards.straightdope.com/t/how-did-this-halloween-decoration-work/220519/6 "2003-12-23T03:37:45Z")
As others have said, it’s ultrasonic: an underwater ceramic transducer vibrates the water into small droplets. This may be the [witch centerpiece](http://wolfstone.halloweenhost.com/HalloweenTech/decwcp_WitchCenterpiece.html) you mean; and here, more about the technology of [ultrasonic misters](http://wolfstone.halloweenhost.com/TechBase/fogus_UltrasonicFog.html). ---
**Author:** ![Eleusis](https://avatars.discourse-cdn.com/v4/letter/e/f4b2a3/32.png) [@Eleusis](https://boards.straightdope.com/u/Eleusis)\ **Post date:** [December 23, 2003, 4:29am UTC](https://boards.straightdope.com/t/how-did-this-halloween-decoration-work/220519/7 "2003-12-23T04:29:22Z")
Thank you all