Overview of dry ice fog

[Only part of the fog from dry ice is actually carbon dioxide gas. The visible fog is from ambient water vapor that is condensed by the extreme cold of dry ice. Without plenty of ambient water vapor, the fog output of dry ice is reduced. This is another reason why dry ice foggers often involve hot water.]

The idea is simple - drop a chunk of dry ice in some water; it will bubble and smoke. In practice, this is a little more difficult, because the dry ice will cool down the surrounding water and start to form a shell around itself of water-ice. Eventually the smoking and bubbling stops. The only way to keep this from happening is to keep the water hot, which increases the rate at which the dry ice is consumed. That's why dry ice isn't really used as often as people think it is.

Theatrical fog machines for dry ice usually take the form of large metal drums filled with water. An electric heater keeps the water warm. The dry ice is placed in some kind of basket, over the water. When you want fog, you lower the dry ice into the water. It rapidly melts, spewing out fog.

Drawbacks

• dry ice is expensive
• dry ice is difficult to store and dangerous to handle
• it takes a lot of dry ice to make fog

Benefits

Another nice feature of dry ice is that it is portable - it does not have an extension cord, or need a bulky machine to make it smoke. {At least you don't need a machine to get some smoke out of it. You do need equipment, often with an extension cord, to keep it smoking over a long time.}

Economics

Dry ice warnings

• Dry ice is frozen carbon dioxide gas. It is fiercely cold, and can easily cause frostbite and other tissue damage.

  In order to reduce the possibility of injury, do not handle dry ice with your bare hands, or allow to come into contact with any exposed skin. This is especially true for damp skin, because the dry ice will use the moisture to freeze itself to you.

• When dissolved in water, dry ice forms carbonic acid. Although mild as acids go, the stuff will eventually attack the container unless it is made from plastic; a less-reactive metal, such as stainless steel; or coated with something unreactive, like epoxy paint. Take this into account if you decide to build a dry ice fog machine. It's nothing to worry about in punch bowls; carbonic acid is also present in soda pop.

• If you use dry ice in water that lacks a heater, the water will cool down. This can be a problem if you are using a light stick in the water to give a glow to the fog, because cold light sticks stop glowing.

  This is a shame, because it sure would be nice to just combine water, dry ice, and a glow stick to get portable glowing fog!

Special notes on some uses

Punch Bowl

In practice, this is a little more difficult, because the dry ice will cool down the surrounding punch and start to form a shell around itself of water-ice. Eventually the smoking and bubbling stops. You might get away with fishing out the little ice-balls and dropping in fresh dry ice every 5 or 10 minutes.

All of this takes a back-seat to the safety issues:

• You need make sure that the dry ice doesn't get into the drinks who don't know how to handle it.
• If dry ice touches lips, or is swallowed, it can cause painful burns.
• Kids, especially, love dry ice smoke, and will try to fish chunks of dry ice out of the punch bowl and play with it.
• Dry ice is denser than water, and usually sinks to the bottom of a punch bowl. This is not guaranteed, as the action of serving or stirring the punch could cause dry ice to float around. Consider wrapping it in a tiny weighted bag of loosely-woven cloth so it will remain on the bottom of the punchbowl.

Drinks