Build Your Own Mini Fogging Cauldron

The best cauldrons are full of bubbling, steamy potions of great magical potential. We don’t have many of those in the real world, though, so sometimes we have to make do with a simulacra. [wannabemadsci] has built just that, with this fogging cauldron prop that uses no fog fluid or dry ice, running solely with water instead.

The heart of the build is a piezo element that vibrates at ultrasonic frequencies to atomize water. They’re available from websites like AliExpress complete with a driver circuit to energize the piezo element. The water is delivered from a wetted fiber wick, and quickly becomes a fog when the piezo is energized.

The disk was installed in a custom PVC water cup with the wetted wick, along with the electronics. The assembly was then lowered into an off-the-shelf plastic cauldron party favor to complete the look. The trick is to mount the piezo element sideways to get a nice-looking distribution of fog. A green LED was installed to light the cauldron from within.

The resulting effect is a sinister-looking glowing cauldron with a steady stream of fog emanating from the top. It’s a great piece of Halloween decor, and as a bonus, it doesn’t require any fancy chemicals to make it work. If you’re thirsty for more, be sure to check out the winners of last year’s Halloween Hackfest. Video after the break.

12 thoughts on “Build Your Own Mini Fogging Cauldron

    1. That’s how our humidifier works.

      One time I bypassed the safety switch that shuts it off if you lift the lid and I stuck my finger in the water above the piezo element. It hurt really bad. Terribly idea.

      One of my kids would want to stick their finger in this cauldron. I’d probably be tempted to as well, thinking “surely it isn’t as powerful as our humidifier…”

      1. A friend of mine did that. He read the instructions that said not to put a finger or anything else into the water jet. So he poked a finger in… “Owwww!” Had a little bruise about 1/8″ diameter. I assume the focused ultrasonic sound waves attempted to rip his finger tissue apart, like they do the water at the top of the little jet they make rise up from the container.

  1. Wow, that’s very cool. Now all it needs is a little audio circuit to make a bubbling sound. And maybe RGB LEDs to turn a malevolent red now and again. I don’t normally make a fuss about Halloween but this might tempt me next year.

  2. I wanted to do something like this on halloween, but the ultrasonic fog generator I got is splasing too much water outside. If I put it in a deeper container then very little fog escapes.

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