Every group of friends has that one person to go to for tech advice: what kind of TV to buy, the right HTML tags to pimp out a MySpace page, and so on. Believe me, I would know. But although I consider myself fairly willing to share the tech wealth, my powers pale in comparison with the sage wisdom dispersed in the "Ask a Geek" feature found in each issue of Popular Science.

The Bubbling Cauldron

Want a real witches’ brew? Mix soap-bubble solution with dry ice, or use liquid nitrogen for bubbles that release fog when they pop. In the following video, PopSci’s contributing mad scientist, Theodore Gray, uses the help of a few young assistants to create cauldrons of toil and trouble.

Here’s how it’s done: