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Ever wondered how Halloween prop fog happens…and where it came from in the first place? Contributor David Lay dishes the juicy scoop below.
Like a lot of things (myself, for example), fog machines have been around for…well, let’s just say a while.
Originally these cool little gadgets were designed to control insect populations by “fogging” an area with oil. The original version was a simple machine: pump oil into a heated metal chamber where the oil was vaporized, then the pressurized vapor exited out of a small opening. As it hit the cooler air outside, this vapor condensed into tiny droplets; hence, fog.
Of course, it didn’t take long for stage and screen to pick up on the fogger to create fogs and mist for plays and movies. But the oil was at best a messy inconvenience, and at worst a health hazard. Can you say “exogenous lipoid pneumonia”? (No? Never mind.)
Water-based Fog Juice: Glycerin
However, in the late 1970’s, someone figured out that you didn’t have to use oil. A water-based material having similar properties as oil but much safer could be used instead.
The machine was similar (check out Rosco’s web site for a really good article on how fog machines work) but required better control for the heating chamber, since the material would form some pretty nasty compounds if over-heated.
The first stuff to be used for this purpose was a common material called “glycerin” or “glycerol” dissolved in water. The mixture was usually about twenty to thirty percent glycerin.
The nice thing about glycerin being used in a fog machine was that glycerin occurs naturally in the body. The body uses glycerin to “tie up” fat molecules so they can be stored for future use. (Some of us have a lot of glycerin in our bodies, thank you very much fast food restaurants!)
It is also water soluble, so if you breateh it, it doesn’t accumulate in your lungs. It even has a sweet smell and flavor to it. That’s because it is, technically, a carbohydrate, or sugar. Not table sugar, but a sugar none the less. In fact, it has about 60% the sweetness of table sugar.
And get this: You can run down to the local drugstore and buy it off the shelf.
Drawbacks of Glycerin as Fog Juice
O-o-o-o-h, but you just knew there was a drawback, didn’t you? This is the one reason fog machine manufacturers don’t use glycerin anymore: because glycerin is a carbohydrate, little beasties like bacteria and mold will eat it and thrive. If you use it in your fog machine, then small amounts of glycerin will eventually deposit on everything in the area where the fog machine is used.
If you use it in your home, you could very well be feeding the mold and microscopic animals that you try to get rid of (some of you may have heard of this ritual – it’s called “cleaning” your house).
Yuck. So, back to the drawing board. What to do? Solution: Use a substitute that has similar properties as glycerin, but little critters won’t eat it.
Artificial Fog Juice
It turns out that there are a couple of other compounds out there that have similar properties as glycerin, but aren’t natural products that feed bacteria and mold. Interestingly, they are put into a class of compounds called “glycol”, but don’t be fooled by their name.
They are, in fact, alcohols or alcohol ethers that are not only non-toxic to breathe (but don’t drink the stuff, please) and not harmful to furniture, but they can also be mixed in such a variety of ways that you can even control the amount of time the fog “hangs” around.
The companies that make fog machines prefer to sell their own proprietary “fog juice” made from these compounds. They do this not just to keep a corner on the market, but for safety as well. Their machines are designed to work optimally with a particular fog juice mix.
The drawback to these compounds is if they are over-heated in the absence of water, they will make some pretty toxic stuff. Therefore, only use the fog juice as directed.
So, Can I Make Fog Juice?
This begs the question: can you make your own fog juice? Answer: A hesitant yes. However, I don’t recommend it – and if you do make it, bear in mind that you make it at your own risk.
Keeping in mind the manufacturers of the fog machines will disown you if you do, here’s how to make the ol’ tried and true glycerin mix: Simply mix 2 parts glycerin with 8 parts water. For a heavier fog, mix 3 parts glycerin to 7 parts water.
DON’T use a mixture greater than 30% glycerin. Also, use distilled water, not tap water. Tap water will eventually ruin your fog machine.
And finally, if you use it indoor, get out the Mr. Clean. Else, you will suddenly be very popular with mold.