A Simple Guide To Fog Dispersion
The Purpose Of Fog
No matter how expensive your fog machine, no matter what label is on your fog fluid jug, the best fog machine and the best fluid is worthless if it doesn't enhance your light show. That's the sole definition of fog...to enhance your light show. Period. If it doesn't do that, than you have wasted your money, effort and time.
Fog doesn't have to be a thick cloud that nobody can see through to be effective. In fact, that thick cloud of fog usually prevents your light beams from passing through and what good is that? Sometimes you may want a sudden, huge, thick cloud of fog for a dramatic moment, but most of the time you want steady, almost unnoticeable fog in the air in front of your stage area so your light beams are seen while passing through it and moving around.
Fog Versus Haze
Although the first commercial machines on the market in the late 60's and early 70's were "Fog" machines, the "Haze" machine has been around almost as long in the theater industry.
Here's the major difference between a fog machine and a true haze machine: A fog machine vaporizes the fluid with heat and a haze machine does it in a compression chamber without heat.
In a fog machine, the fluid is pumped through the heater core where it vaporizes and is forced out the front in it's vaporized state. When the temperature of the heater core drops below the temperature necessary to vaporize the fluid, the pump is disabled so you can't shoot out hot liquid on the crowd.
In a haze machine, the fluid is pumped into an enclosed chamber where an air compressor (similar to what you inflate your tires with) blasts the fluid into a vapor, then a small fan blows that vapor out the front of the machine. A haze machine never shoots out a thick cloud like a fogger can. In fact, you rarely see haze in the air.
Since fog machines are drastically more popular for the club and DJ industry and since the name of this article is "About Fog Dispersion", I will concentrate on fog instead of haze.
How And When Fog Came About
I remember the mid 70's, when the first Disco's started using fog. This was before there was such a thing as a "Mobile DJ". The more affluent clubs had the only commercial fog machines on the market at that time and they were made by Rosco in New York. The machines I remember seeing first were the standard black square box with a hand pump built in, similar to the hand pump on a yard sprayer. These more affluent clubs had several of these fog machines spread around the dance floor. They would fill them up before they opened and again during the night if they used a lot of fog.
The less affluent night clubs and a few bands that liked the look of the fog but couldn't afford the expensive Rosco fog machines started using a converted yard insecticide fogger that was available soon after the Disco craze began. They had a white, round gallon jug on the bottom and the black heater housing screwed on top of that. They were considerably less than the commercial Rosco foggers and they worked really well. They even had one huge advantage. They held a full gallon of fluid, so they didn't have to be refilled during the night. The Rosco machines started coming with a remote switch to turn the fog on, but you still had to pump up the tank during the night. These cheaper converted yard foggers soon had a remote switch available for them too.
Regardless of which style of fogger you chose back then, fog was heavily used and loved. It started with the Disco era, but continued long after that. Can you imagine going to a concert today without fog? It would just be boring. We are all used to seeing it. We expect it now. Fog is equated to excitement and it works.
How To Get It Where You Want It
One problem that has always been around is how to get the fog exactly where you want it... When you want it there.
Step1: Clubs started with one fogger in the DJ booth and pointed it towards the middle of the dance floor. It was in the DJ booth so it could be refilled easily during the night.
Step2: Big clubs started placing 2 to 4 foggers in the DJ booth and aiming them at the center of the dance floor or toward strategic areas that needed more fog. Battling air conditioner vents and intakes was always frustrating. You could aim all 4 foggers toward the left side of the club and if the air conditioner intake was on the right side, it pulled the fog across the dance floor evenly. That situation was ideal, but hard to find.
Step 3: To battle air flow from air conditioners or open ventilation, some larger clubs started placing multiple foggers throughout the dance area ceiling. Each would be aimed to cover a specific area or to battle a specific problem like an air vent. The DJ would have a switch for each fogger in his booth and he would press the button for whichever fogger was needed to fill a light spot. The downside was that someone had to climb up on a ladder every night to fill each fogger.
Piping the fluid to each fogger
This next step was created by necessity. Having multiple foggers scattered around a club was the best answer so far for keeping fog spread out evenly over a dance floor, but having to climb up ladders daily to fill them was a nuisance. So someone had the idea to keep a 55 gallon drum of fog fluid on the ground floor and pump it to each fog machine via a small plastic tube. It was indeed a good idea. Piping fluid to multiple foggers was the best idea going, but it still had it's downsides. Whenever a machine failed, you still had to get up on a ladder and pull it down and put up a replacement.
Ducting The Fog
I saw the first fog ducting system in the early 80's. It was crude, but it worked very well. A local club owner had gotten tired of battling the multiple fogger problem and the air flow problem for years and decided to try buying one big fog machine to leave in the DJ booth and he would duct the fog to many areas over the dance floor and point the ducts down because that's where you want the fog. He spent a few months tweaking his invention and the results are described below.
The Fog Machine & The Distribution Box
Start out by getting the largest fog machine you can. Since fog has moisture in it, you should not build the distribution box out of wood. Most do it yourselfers use a jumbo ice chest. Cut a round 4" intake hole on one end and set the fog machine about 4 inches away from this hole, aiming the fog into the intake hole. You have to set the fog machine about 4 inches away from the intake hole because a fog machine requires the output of the machine to mix with air to form the best fog.
The Distribution lines
If you just connect eight 4" distribution lines to this box, the fog will not come out evenly. It may not come out at all. There are two thoughts on how to force air through the distribution lines. One way is to buy one big fan like the one inside your home air conditioner and mount it inside this box to force the fog out ONE hole and into another box that has the eight 4" distribution lines attached. The other way is to mount all eight 4" distribution lines to this box and mount a 4" box fan inside the box for each line attached. (Example; you cut a 4" round hole in the side of the box and mount a 4" box fan inside the hole to blow air out. You then attach your 4" distribution line to the outside of this hole to carry the forced air out to the dance area.)
Having seen both types of distribution box in action, I prefer the one with a 4" box fan per hole. It is quieter and more efficient.
Now what about these 4" distribution lines? You're gonna love this. The best thing I've seen for this is the cheap, thin, black sewer hose that comes in 100 foot rolls at Home Depot. They have two types. One is totally enclosed and will only allow the fog to come out of the end of it. The other type has tiny holes all over it and will allow the fog to drift out all over it. You definitely want the enclosed tube to carry the fog from the distribution box to the dance area. If you just want to aim it down and have the fog come out, you're done. If you want to connect a piece of the slotted tube at the dance area and run it around the ceiling so fog drifts out lightly and spread out, try that.