Water Only Fog Machine
Everybody loves fog, Theatrical Fog that is - Especially at Halloween, and there are many ways to make it:
1. Dry Ice was my first introduction to fog - Dry Ice dropped into hot water provided LOTS of dense low-lying fog. It was great, but you had to go get the dry ice and be very careful handling it. When I lived in San Jose, California there was a company called Able Carbonic near the airport that had a Dry Ice Drive Through around Halloween - it was great!. You could pull your car right into their warehouse and purchase however much dry ice you wanted without leaving your car.I've built a couple of contraptions to make using dry ice fog easier.
A safety note - Dry Ice is Carbon Dioxide and in addition to being extremely cold (-109.3°F or -78.5°C), causing instant cold 'burns' on contact (use insulated gloves), it can present a suffocation hazard because the carbon dioxide gas evaporating off of it will displace the normal air around you and deprive you of oxygen. I once had a small room filled with dry ice fog and it became apparent by the coughing and faster breathing that there was too much carbon dioxide in the room - Exit NOW if you find yourself in such circumstances!
2. Heated 'Fog Machines' that heat glycol-based or glycerin-based 'Fog Juice' to spray out a plume of white smoke/fog. I like to think of these as smoke machines more than fog machines. These are used at concerts to make the beams of light/lasers show up, and traditional low lying fog too . My commercial photographer friend introduced me to this type of 'fog' machine. He had a professional Rosco unit that was really built like a tank and pumped out tons of smoke. I eventually purchased a Rosco unit and have since purchased consumer 'fog machines' of various sizes at big box retailers on clearance after Halloween so that now I have 3 (or more, not really sure how many I have ;-).
'Fog Machine' fog tends to disperse all around you as if in a London Fog, so if you want it to hang near the ground you have to chill it. There are tons of Insturctables how to build one of these fog chillers.
3. Here is the new fog method - Ultrasonic Atomization. This is where a piezoelectric disk is electrically pulsed to vibrate at ultrasonic frequencies with a shallow layer of water over it. The surface of the water breaks up into fine droplets; fog. Ultrasonic humidifiers use this method to produce the visible mist being blown out of them. Many years ago I saw the fog potential of ultrasonic humidifiers and 'plumbed' the output of one of them via a hose into a jack-o-lantern to have fog creeping out of its mouth.
Fast forward to today. You can get high capacity pond foggers that will produce large amounts of fog (using >2 liters of water an hour). These high output atomizers are not cheap (~$200) but dump out tons of fog, low lying fog, without any carbon dioxide gas. No consumables but water and electricity!
Step 1: Materials
You will need:
5 gallon bucket and lid
4 inch diameter dryer duct (larger diameter is OK)
Computer cooling fan and matching voltage plug-in AC adapter
Machine screws and nuts to fasten fan in place
Empty 2-liter soda bottle
One 12 Gauge steel wire (a T-bar ceiling hanger wire works)
12-Jet Ultrasonic Water Vaporizer (Mister) and associated power supply
Remote Controlled AC switch (optional)
Heat-shrink tubing or electrical tape
Frozen Ice packs or Water Ice (as opposed to dry ice)
Drill Motor and Drill Bits
Utility Knife or Sabre Saw
Soldering iron (optional)
Heat gun (optional)
Step 2: Cut Some Holes in the Lid
Take the bucket lid and mark out locations for the fan (main opening plus mounting holes), dryer duct and also a hole for the power connector of the atomizer to pass through the bucket lid.
Cut out the openings using a utility knife or sabre saw. Cut the duct opening about a 1/4" smaller in diameter than marked so the spiral duct will fit snugly in the hole.
Step 3: Prep the Fan
Cut off the end of the cord of the Plug-in AC adapter and strip the wires bare. Connect the stripped AC power supply lead wires to the fan leads. Match the polarity (+) to (+), (-) to (-). if they don't have matching colors you may have to use a voltmeter to determine polarity or just go with trial and error.
You can solder or just twist the wires and use heat shrink tubing over the connection or just electrical tape.
Step 4: Mount the Fan and Duct to the Lid
Use machine screws, nuts and washers to fasten the fan to the top of the bucket lid with the airflow into the bucket. Since the duct is the spiral type it can just be twisted 'into' the opening to fasten it in place.
Step 5: Set the Atomizer Head in the Bucket
Place the atomizer into the bucket, threading the power cable up though the hole in the bucket lid cut for the connector. After the cable is through the lid pack the connector opening with some foam to seal it off. Alternately you could cover the opening with duct tape.
Add water to the bucket until the level is per the operating instructions or until the 'low water' sensor is just covered.
Step 6: Auto Fill
To keep the fog machine operating continuously the water needs to be replenished. An inverted 2-liter soda bottle will do the trick. It acts like the 5 gallon jug on top of a water cooler (bubbler).
Bend a wire support frame out of 12 gauge wire and hold the bottle in place with a zip tie. Bend a upside down U'-shaped hook in the top of the wire. Select the length of wire above the top of the bottle so that the mouth of the bottle is at the water level you want to maintain.
Cut a slot in the top of the bucket lid so that the 'u' bent hook can fit through. Position the hook so that moving it to one side will catch on the lid and suspend the bottle. Fill the bottle with water and hang it in position.
Step 7: Energize!!!!!
Power up the atomizer. You can watch it work and fill the bucket partly with fog. The fog will not overflow the bucket, it just settles into the bottom of the bucket. Any fog moving up toward the lip of the bucket just evaporates before it goes over it. Air movement is needed to get the fog expanding and billowing. Power up the computer fan. You should now have fog pouring out of the duct!
If you want you can plug the atomizer power supply and fan power supply into a remote controlled switch. That way you have fog on demand!
The atomizer is using about 300W of power to atomize the water into fog and a large portion of that will go into the water as heat. So in order to keep the submerged atomizer from overheating you will have either run it for very short periods of time or add frozen ice packs or even just frozen water ice to keep the water temperature (and the atomizer) cool.
Now you have a virtually unlimited supply of fog - so put it to good use, like one of my favorites; a bubbling cauldron - but that's an Instructable for another day!