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Scare the trick-or-treaters this Halloween with a home-built fog machine.

A do-it-yourself Halloween could be as simple as positioning a few scary props at strategic locations throughout the home, or as elaborate as a movie-grade haunted house. But one thing you'll definitely want for Halloween? Some creepy fog to set a mysterious mood. Build this DIY fog machine to make that vision a reality.

The best part is that you don't have to fork over a bunch of cash to rent a fog machine. Our method is even cheaper than the ol' dry ice-in-a-bucket-of-water routine, since you can build your own fog-making rig from a few bottles and some chemicals. All in all, it'll only cost you a few bucks.

•One large candle, preferably with multiple wicks

•An aluminum pie plate

•The top of a 2-liter plastic soda bottle

•A gallon of distilled water

•A bottle of glycerin

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Now that you've got all your ingredients, it's time to build your very own fog machine.

Step 1: Make your "fog juice" by mixing a solution of one part glycerin to three parts distilled water. The "fog" is created when the solution is heated to the point of evaporation. The process leaves an accumulation of dense vapor, which becomes cloudy when it hits room-temperature air.

Step 2: Build your haunted-house fog machine by cutting the top off a 2-liter soda bottle and taping the narrow end onto the small aluminum pie plate, creating a cone shape.

Step 3: Position your fog machine over the lit candle. This can be done by taking an empty metal coffee can or a large soup can—without the lid, of course—and poking out several vent holes around the base of the can's sealed end, perhaps with the pointed end of an old-fashioned metallic can opener.

Step 4: Drop the candle into the can and light it. Place the pie tin/fog machine over the can's open top. Add a teaspoon or so of fog juice. That should produce enough fog to fill a good-sized room. To replenish the fog, just pour additional teaspoons of fog juice into the fog machine as needed.