Have you ever made your own fog/bubble/snow juice?  It's extremely simple to do.  All it takes is a trip to the drugstore for distilled water and a few bottle of glycerin.

I made about 2 quarts of it for under $4.00.

• 1 Quart of distilled water (32 oz)
• 4 oz food grade or high grade glycerin

You can add more glycerin for thicker fog or less for lighter fog.  If you plan on having a lot of fog this if probably the most economical.  I have heard you can add food coloring to the mix to have colored fog (like red) but have not tried it.

Thanks to Bob Chrisp, here is even more information on making fog juice:

Here is a good article on fog/bubble/snow juice:

Atomized Glycols

Many commercial smoke machines use 'fog juice' that consists of glycols, glycerin, 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. Some homemade recipes for fog juice are:

1. 15%-35% food grade glycerin to 1 quart distilled water
   125 ml glycerin to 1 liter distilled water
   (glycerin creates a 'haze' at concentrations of 15% or less and more of a fog or smoke at concentrations higher than 15%)
2. Unscented mineral oil (baby oil), with or without water
   (I can't vouch for the safety of using mineral oil for fog juice)
3. 10% distilled water: 90% propylene glycol (dense fog)
   40% distilled water: 60% propylene glycol (quick dissipating)
   60% water: 40% propylene glycol (very quick dissipation)
4. 30% distilled water: 35% dipropylene glycol: 35% triethylene glycol (long-lasting fog)
5. 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 glycerin/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.

Important Points

• 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, glycerin, 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.

If you are a visual person, here's a link to a video describing how to make a solution for producing gigantic bubbles: 

 http://www.parentdish.com/2007/10/12/how-to-make-gian-soap-bubbles-video/

Finally, here is a bubble making recipe from Kids Domain:

This project gives children as well as adults the chance to make their own homemade bubbles.

Note: As in all recipes, results can vary depending on humidity, conditions, etc. Please try any recipe out before attempting in a group setting.

This project is rated VERY EASY to do.

What You Need

• 1/2 cup Dishwashing detergent (120 ml)
• 4 1/2 Cup Water (1.1 liter)
• 4 Tablespoons glycerin (available at pharmacies) (60 ml)
• Container with a tight fitting lid in which to keep the bubbles
• Measuring devices
• Spoon

1. Gather all your supplies.
2. Measure out the water, detergent, and glycerin into container.
3. GENTLY stir the mixture together. If a foam forms, gently skim it off the top.
4. Find something with which to blow bubbles and begin to have fun.

Note: The longer you let the mixture set, the larger the bubbles are and the longer they seem to last.