Of the two methods described here, the dry ice/warm water method is the easiest. It is illustrated in the featured video on this site. The mineral oil/compressed air method is more complicated, as it requires having an air compressor. Of course, if you already have a compressor, this is an easy project as well. Both of the methods have their advantages and disadvantages. Dry ice is dangerous to handle, and the other method is a bit noisy. With the instructions given below, you will be able to put together a fog machine for Halloween or your next party.

Materials:

1. Styrofoam cooler, about 12 quart size
2. 12-volt fan motor salvaged from a computer, with mounting screws, nuts and washers
3. 12-volt battery
4. 1 ft of 2" plastic pipe
5. Pipe insulation for the interior of the 2" pipe
6. 2-3 ft of 1 1/2 plastic pipe, flattened on one end using a torch
7. Pipe fittings: 2- 1 1/2" Male thread x 2" female slip couplings"; 1-1 1/2" Female Slip x 1 1/2" Female- thread coupling; 1 - 1 1/2 Male thread x Male thread coupling
8. Pipe glue, teflon tape

Tools Needed:

1. Razor knife
2. Screwdriver
3. Black permanent marker
4. Pliers
5. 12-volt battery, wires and wire nuts

1. With the marker, trace the outer diameter of the 1 1/2" male thread fitting on one end of the cooler, about 2/3 the way up from the bottom.
2. Carefully cut the area out for the pipe insertion.
3. With the marker, mark the circular diameter of the fan on the other end of the cooler and then cut out the space for insertion of the fan.
4. Mount the fan. Use washers on the screws as the cooler wall is fragile. As shown in the video, you could also use wire to mount the fan. Do whichever technique you find the easiest.
5. Put the insulation in the 2" pipe.
6. Put the fittings on the 2" pipe, so that you have male screw fittings on each of the ends, use the glue.
7. Put the female fitting on the 1 1/2" pipe with the glue.
8. Insert the male threads from the 2" pipe in the cooler and screw on the 1 1/2" male thread x male thread fitting on the inside of the cooler to fasten in the pipe on that end. Use the teflon tape.
9. Teflon tape the other end of the 2" pipe and screw on the 1 1/2" pipe extension.
10. Connect the fan to the battery with the wire and wire nuts.

Operation

1. Put the dry ice in the cooler.
2. Pour warm tap water over the ice and close the lid. You may want to put a weight on the lid to keep it down.
3. Turn on the fan to direct the fog. Connect the battery to start the fan to direct the fog from the cooler.

Materials:

1. 2 gallon plastic food bucket with a snap-on lid
2. 2 ft. 3/8 inch copper tubing
3. Unscented mineral oil, 4 quarts
4. 1 1/4 inch ABS barbed Tee fitting
5. Compressor, for the air supply, at least a 4 HP with a 12 gallon tank
6. Tubing to connect the air compressor to the copper tubing

Putting it together:

1. Drill a hole in the center of the bucket lid for the 1 1/4 inch ABS tee fitting
2. Drill another hole on the side of the bucket lid for the 3/8 inch copper tubing to enter.
3. Bend the copper tubing so it will sit as a circlel in the bottom of the bucket.
4. Pinch and solder the end of the tubing shut.
5. Drill four 1/32-inch holes in the tubing on the bottom side.
6. Clamp or tape the tubing it to the lid so it stays in place.
7. Attach 1/1/4" flexible plastic pipe, to length needed

Pour mineral oil into the bottom of the bucket so that it fully covers the copper tube. Attach your air compressor (at around 30-40psi) to the copper input tube, and you should notice fog start to roll out from the exit fitting in about 20 seconds or so.

This produces a good amount of fog, which does not rise, and the compressed air pushes out the fog so you don't need a fan. The small fog tube is easier to conceal than the much larger ones used on heater type fog machines. If you run the setup for a couple of hours you will detect a very fine oil layer at the exit of the fog tube, but its not messy at all.

The disadvantage of this setup is it uses a lot of air and the compressor is very noisy. You can remotely locate the compressor if you have enough hose. There will be hissing and bubbling noises from the fog machine itself, but they can add to scary sound effects!