Dry ice can produce vigorous bubbling water and voluminous flowing fog when combined with hot tap water. For example, 5 pounds of dry ice in 4 to 5 gallons of hot water will produce the most significant fog for the first 5 to 10 minutes. There will be far less fog for the next 5 to 10 minutes as the water cools down and the Dry Ice decreases. As the water cools, the fog becomes wispier. Dry ice makes fog because its cold temperature, -109°F or -78°C, immersed in hot water, creates a cloud of true water vapor fog. When the water gets colder than 50°F, the dry ice stops making fog but continues to sublimate and bubble. The fog will last longer on a damp day than on a dry day.
For each 15-minute period, put 5 to 10 pounds of dry ice into 4 to 8 gallons of hot water. This will make lots of fog depending upon the temperature of the water and the size of the pieces of dry ice. Hotter water will make more fog. Boiling water will add its own rising steam to the vapor cloud. If there is no steam, the fog will flow downhill and in the direction of any air movement. A small fan can help control the direction. Smaller pieces of dry ice with more surface area produce a greater fog volume and cool the water down much faster. In both cases, the result is more fog for a shorter amount of time. Keep the water hot with a hot plate, electric skillet, or some other heat source to produce fog for a longer time. Otherwise, when the water gets too cold, it must be replaced to continue the fog effects. If the container is filled with water, the fog will flow over the sides the best. But the dry ice sublimation will vigorously bubble the water and splash it out. Even a ¾ filled container will splash some, so place the container where spilled water will not ruin anything. The water vapor fog will also dampen the area it flows across. Be careful because, after some time, floors do get slippery.
DRY ICE FOG MACHINES
A theater fog machine is generally a 30 to 55-gallon metal or plastic water container with a 110-volt or a 220-volt water heater to keep the water hot. Dry ice is placed in a bucket with holes to allow hot water to enter. Fog billows out when the hot water contacts the dry ice. The resulting water vapor fog is gently blown by a fan and directed to the desired area by an air duct tube. Fog stops when the water no longer contacts the dry ice. Some fog machines pump heated water over a tray holding the dry ice. The amount of fog produced is limited to the amount of water the machine can heat – the higher wattage and larger the water container is, the more incredible amount of fog delivered.