Smoke, fog, haze, and mist machines create some new special effects. Have you ever wondered what makes the smoke? Have you ever wanted to create the effect yourself? If so, you are in luck, as we will reveal these mysteries. However, we will warn you that a little knowledge is a dangerous thing! If misused, the equipment and chemicals used to generate simulated smoke can be hazardous (toxic, burn hazard, asphyxiation hazard, fire hazard, etc.). Also, all types of smoke generators will trigger smoke alarms. I’m telling you how the effects are created, not advising you to make your own smoke. If you are a severe do-it-yourself type, read the article and then please follow the links I have provided to the right of this article, which include specific instructions and warnings from professionals and experienced amateurs.
Aside from using a smoke machine, this method is the simplest for most people, both in practice and obtaining materials. Dry ice is stable carbon dioxide. You can make a dense fog by adding dry ice to hot water or steam. The carbon dioxide is vaporised, creating a mist, and the rapid cooling of the surrounding air condenses water vapour in the air, adding to the effect.
Why you put a piece of dry ice in water, you’ll see a cloud of what looks like smoke or fog billow away from the surface and down toward the floor. The cloud is not carbon dioxide, but actual water fog.
We know that dry ice is incredibly fun to use in experiments – it’s because of the awesome fog you get when you combine the ultra-cold ice with warm water! Now if you could only figure out a way to actually grab and hold that elusive smoke in your hands. With the Dry Ice Smoking Bubbles experiment, you can! By creating smoke-filled bubbles that you can hold in your hands, you make dry ice a fun experience that everyone can really “grasp.”
Dry ice is stable carbon dioxide (CO₂). It has the unusual property of ‘subliming’, that is going from a solid to a gas without passing through a liquid phase, and this is how it gets the name dry ice. The product can only exist at -79C, and it maintains this temperature by sublimation. In the UK the CO₂ in dry ice is from a recycled source and so is not contributing to global warming.
Dry ice, when combined with hot tap water, can produce vigorous bubbling water and voluminous flowing fog. For example, with 5 pounds of Dry Ice in 4 to 5 gallons of hot water, the highest amount of fog will be produced 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 volume of Dry Ice diminishes. As the water cools, the fog becomes wispier. Dry ice makes fog because of its cold temperature, -109.3°F or -78.5°C, immersed in hot water, creates a cloud of real water vapour fog. When the water gets colder than 50°F, the Dry Ice stops making fog but continues to sublimate and bubble. The haze will last longer on a damp day than on a dry day.
Dry Ice is CO2 gas compressed into a solid. It has a surface temperature of -78oC. Touching the Dry Ice directly with your skin will freeze cells and cause injury similar to a burn. For this reason, insulated gloves should be worn at all times when handling Dry Ice.
We manufacture Dry Ice in several different product types: blocks, slices, and pellets. What product type you should use will depend on whether you are using a smoke machine or just creating the fog effect using your containers. We sell the dry ice blocks and slices in units of 10kgs, and dry ice pellets in units of 3.5kg, 8kg, and 10kg.
Dry ice was my first introduction to fog – Dry Ice dropped into hot water provided LOTS of dense low-lying fog. It was great, but you had to get the dry ice and be very careful handling it. When I lived in San Jose, California there was a company called Able Carbonic near the airport that had a Dry Ice Drive Through around Halloween – it was great!. You could pull your car right into their warehouse and purchase, however much dry ice you wanted without leaving your vehicle. I’ve built a couple of contraptions to make using dry ice fog easier.
A safety note – Dry Ice is Carbon Dioxide. In addition to being extremely cold (-109.3°F or -78.5°C), causing instant severe ‘burns’ on contact (use insulated gloves), it can present a suffocation hazard because the carbon dioxide gas evaporating off of it will displace the healthy air around you and deprive you of oxygen. I once had a small room filled with dry ice fog, and it became apparent by the coughing and faster breathing that there was too much carbon dioxide in the room – Exit NOW if you find yourself in such circumstances!
I have heated ‘Fog Machines’ that heat glycol-based or glycerin-based ‘Fog Juice’ to spray out a plume of white smoke/fog. I like to think of these as smoke machines more than fog machines. These are used at concerts to make the beams of light/lasers show up, and traditional low lying fog too. My commercial photographer friend introduced me to this type of ‘fog’ machine. He had a professional Rosco unit that was built like a tank and pumped out tons of smoke. I eventually purchased a Rosco unit and have since purchased consumer’ fog machines’ of various sizes at big-box retailers on clearance after Halloween so that now I have 3 (or more, not really sure how many I have.
‘Fog Machine’ fog tends to disperse all around you as if in a London Fog, so if you want it to hang near the ground, you have to chill it. There are tons of Instructables on how to build one of these fog chillers.
How Dry Ice Produces Water Fog
Dry ice is the solid form of carbon dioxide, a molecule that is found as a gas in the air. Carbon dioxide has to be cooled to at least -109.3 °F to become a solid. When a chunk of dry ice is exposed to room temperature air, it undergoes sublimation, which means it changes from a solid directly into a gas, without melting into a liquid first. Under ordinary conditions, this occurs at the rate of 5-10 pounds of dry ice converting into gaseous carbon dioxide per day. Initially, the gas is much colder than the surrounding air. The sudden drop in temperature causes water vapour in the air to condense into tiny droplets, forming fog.
Only a small amount of fog is visible in the air around a piece of dry ice. However, if you drop dry ice in water, especially hot water, the effect is magnified. The carbon dioxide forms bubbles of cold gas in the water. When the bubbles escape at the surface of the water, the warmer moist air condenses into lots of fog.
The fog sinks toward the floor both because it is colder than the air and because carbon dioxide is denser than air. After a time, the gas warms up, so the fog dissipates. When you make dry ice fog, the concentration of carbon dioxide is increased near the floor.
When dry ice is added to warm water, dense white fog is immediately generated. The white fog is an aerosol of tiny water droplets, just like fog created naturally. What’s happening is that the freezing dry ice is subliming from stable to the gaseous phase and bubbling through the water. In so doing the CO₂ gas leaves the water container which has a substantial amount of moist air above it. The cold CO₂ vapour condenses water molecules in the sky above the box leading to the formation of tiny water droplets which are so small they stay in suspension with the gas. The only difference between natural fog and dry ice fog is the presence of gaseous CO₂ interspersed with the water droplets. CO₂ gas is heavier than air and so tends to carry the white fog towards ground level creating cool effects! The haze will cover the ground, roll downstairs, and swirl when walked through. It will not rise into light beams like glycol type foggers and will not make a fine mist in the air like hazers. Dry ice fog has no odour, contains no chemicals, and leaves no oily residue.
How Do I Make Dry Ice Fog?
Consider using a fog generator – the next question “How is a dry ice fogger operated?” If you are looking to cover a large area, such as a dance floor, you will need 20kg of dry ice which will last for 8-10 minutes. Add dry ice to a container with hot water (50C) and the fog effect will be spontaneous. The fog effect can be halted if too much dry ice has been added to the water so chilling (and ultimately freezing) the water and reducing the humidity of the air above the container. To maximise the fog effect, you need to use warm/hot water. If you want the fog effect to last for a prolonged period, consider adding a source of heat to keep the water-friendly – the container could be a rice cooker or slow cooker on the lowest heat setting. Be careful – if you use the heater on a high setting thermal currents will send the fog into the air spoiling the effect. Candles will not work as the CO₂ will extinguish the flame; after all, CO₂ is used in fire extinguishers!
For every 15 minutes 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. More boiling water will cause more fog. Boiling water will add its own rising steam to the vapour 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 higher volume of fog 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 mist for a longer time. Otherwise, when the water gets too cold, it must be replaced to continue the fog effects. If the container is completely 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 vapour fog will also dampen the area it flows across. Be careful because after some time floors do get slippery.
How Do I Store Dry Ice?
Store dry ice in an insulated container – the better the insulation, the slower the rate of sublimation to CO₂ gas. The best container is the polystyrene box that the dry ice was shipped in. Do not store dry ice in an airtight or glass container. The sublimation of dry ice into CO₂ gas will cause an airtight container to expand, rupture or burst.
The CO₂ gas occupies about 800 times the volume that the dry ice did! CO₂ gas is heavier than air and will sink to low areas and displace air. At elevated concentrations, CO₂ can be fatal as an asphyxiant.
For this reason, always store dry ice in a well-ventilated area – avoid unventilated rooms such as cellars, boat holds and walk-in freezers.
Note: you can store dry ice in domestic (non-walk-in) freezers provided the dry ice is kept in the polystyrene packaging. The dry ice will release CO₂ gas while in the fridge; however, there is no risk of asphyxiation. The freezer will reduce heat transfer into the box and prolong the life of the ice. However, do not store dry ice in walk-in freezers as there is a risk of an accumulation of CO₂ which could cause an asphyxiation risk if the fridge is not used regularly.
The extreme cold may damage some surfaces left in direct contact with Dry Ice. Adhesives may become brittle and break. So please do not let dry ice into contact with kitchen tiles, or other surfaces which are susceptible to damage from the cold.
The best container to transport and store Dry Ice is an ice chest. It will still sublimate 5 to 10 pounds each 24 hours, so plan to pick up the Dry Ice as close as possible to the time it will be used. Dry ice is freezing, so use insulated gloves to handle it. Do not store Dry Ice in your refrigerator freezer. The freezing temperature will cause your thermostat to turn off your fridge. (But it will keep things frozen if your refrigerator breaks down in an emergency.) Do not store Dry Ice in a completely airtight container. The sublimation of Dry Ice to Carbon Dioxide gas will cause any airtight container to expand until a hole opens or it explodes.
Store Dry Ice in an insulated container (e.g. thick styrofoam box). The thicker the insulation, the slower it will sublimate. The poly box storage carton provided with the Dry Ice will hold it sufficiently well for a maximum of 72 hours. The Dry Ice does not need to be stored in a freezer. Due to its short shelf life, we always recommend ordering the Dry Ice for delivery or collection as close as possible to the day of use. NEVER store Dry Ice in a completely airtight container. The sublimation of Dry Ice to Carbon Dioxide gas will cause any airtight container to expand or possibly explode. Keep proper air ventilation wherever Dry Ice is stored. Do not store Dry Ice in unventilated rooms. Dry ice is an asphyxiant, and the sublimated Carbon Dioxide gas will sink to low areas and replace oxygenated air.
Does Dry Ice Melt?
Dry ice is so-called as it does not have a liquid state, i.e. it does not melt. Instead, from the minute it is made, the Dry Ice is all the time slowly reverting back to its original gas form.
What Safety Precautions Should I Take?
- Wear insulated gloves (preferably with a closed cuff) when handling the dry ice.
- Wear eye protection if breaking up larger pieces of dry ice such as blocks or slices.
- Store the box of Dry Ice in a well-ventilated room to prevent the build-up of CO2 in the air.
Healthy air is 78% Nitrogen, 21% Oxygen and only 0.035% Carbon Dioxide. If the concentration of carbon dioxide in the atmosphere rises above 0.5%, carbon dioxide can become dangerous. If you start to pant and breathe quickly, this is an indication that there is too much CO2 in the room. Dry Ice CO2 is heavier than air and will accumulate in low spaces; hence the ventilation should be located at a lower level in the place. Do not enter closed storage areas where dry ice has been or is currently being stored before airing out the storage area completely