One recipe for homemade fog liquid for use in commercial smoke machines combines glycols or glycerine with distilled water. The machine then heats and pressurizes the mixture into the atmosphere to produce artificial fog.
There are a variety of recipes to create different fogs or hazes. The concentration of ingredients determines the thickness of the smoke that a fog machine produces. A concentration of less than 15 percent food-grade glycerine creates a lighter haze, while a concentration of 15 percent or more has a thicker appearance.
A mixture of 90 percent propylene glycol and 10 percent distilled water produces a lasting, dense fog. Dipropylene and triethlyene glycol can also create an exceptionally thick and long-lasting fog at a ratio of 70 percent to 30 percent water. A mixture of 60 percent propylene glycol and 40 percent water is better for a lighter fog that dissipates quickly, while a mixture of 40 percent glycol and 60 percent water is ideal for producing a faint fog with a very speedy dissipation.
Fog machine operators should use caution when handling chemicals because some mixtures are flammable. Additionally, they should not substitute propylene glycol with ethylene glycol, which is poisonous. Users should not operate fog machines in rooms with smoke detectors because they are sensitive to all forms of artificial smoke.