To make fog fluid, also commonly called fog juice, a basic recipe is to mix a quart of distilled water with 15- to 35-percent food-grade glycerin. Another recipe is to mix distilled water with propylene glycol. A mixture of 10-percent distilled water and 90-percent propylene glycol creates a dense fog, while a mixture of 60-percent distilled water and 40-percent propylene glycol makes a quickly dissipating fog.
Fog fluid is the liquid used in commercial smoke machines, which heat the glycols. As the machine pressurizes the heated glycols, it forces them into the air and creates a fog. To create a fog that lingers, use a mixture of 30-percent distilled water with 35-percent dipropylene glycol and 35-percent triethylene glycol. For an alternative recipe for dense fog, mix 30-percent distilled water with 70-percent dipropylene glycol.
It is important to only use food-grade glycols and pure materials. Never substitute other chemicals when making fog fluid. Even the correct types of glycol may be toxic in large doses, and most are flammable. Use extreme caution when introducing homemade fog fluid into the heating environment of a commercial fog machine. Never use ethylene glycol, found in antifreeze, to make fog, as it is highly toxic.