Many commercial smoke machines use 'fog juice' that consists of glycols, glycerine, and/or mineral oil, with varying amounts of distilled water. The glycols are heated and forced into the atmosphere under pressure to create a fog or haze. There are a variety of mixtures that may be used. See the reference bar to the right of this article for Material Safety Data Sheets on some example types. Some homemade recipes for fog juice are:
- 15%-35% food grade glycerine to 1 quart distilled water
- 125 ml glycerine to 1 liter distilled water
(glycerine creates a 'haze' at concentrations of 15% or less and more of a fog or smoke at concentrations higher than 15%)
- Unscented mineral oil (baby oil), with or without water
(I can't vouche for the safety of using mineral oil for fog juice)
- 10% distilled water: 90% propylene glycol (dense fog)
40% distilled water: 60% propylene glycol (quick dissipating)
60% water: 40% propylene glycol (very quick dissipation)
- 30% distilled water: 35% dipropylene glycol: 35% triethylene glycol (long-lasting fog)
- 30% distilled water: 70% dipropylene glycol (dense fog)
The resulting smoke should not smell 'burnt'. If it does, likely causes are too high of an operating temperature or too much glycerine/glycol/mineral oil in the mixture. The lower the percentage of organic, the less expensive the fog juice, but the fog will be lighter and will not last as long. Distilled water is only necessary if a heat exchanger or other tubing is used in the system. Using a homemade fog mixture in a commercial machine will almost certainly void the warranty, possibly damage the machine, and possibly pose a fire and/or health hazard.
- This type of fog is heated and will rise or disperse at a higher level than dry ice or liquid nitrogen fog. Coolers can be used if low-lying fog is desired.
- Changing the mixture or conditions of dispersion of atomized glycols can result in many special effects that are difficult to achieve with other simulated smokes.
- Glycols can undergo heat denaturation into highly toxic substances, such as formaldehyde. This is one of the major problems with homemade smoke machines - they may operate at a temperature that is incompatible with the substances being used. Also, this is a danger with homemade fog juice used in commercial machines.
- Glycols, glycerine, and mineral oil can all leave an oily residue, resulting in slick or sometimes slightly sticky surfaces. Be aware of the potential safety hazards, especially since the smoke may limit visibility. Also, some people may experience skin irritation from exposure to glycol fog.
- Some glycols are toxic and should not be used to create smoke. Ethylene glycol is poisonous. Some glycols are sold as mixtures. Medical or pharmaceutical grade non-toxic glycols only should be used in smoke machines. Do not use antifreeze to make a fog mixture. The ethylene glycol types are poisonous and the propylene glycol types always contain undesirable impurities.
- If water is used, it needs to be distilled water, since hard water deposits can damage the atomizer apparatus.
- Some of the chemicals that can be used for this type of smoke are flammable.
Ready to learn about 'real' fog? Then read about how water vapor is used to simulate smoke.