Effectively using atmospheric effects on stage can bring a production a moment to a whole new level of engagement from audiences. Creating perfect beams of light and spectacular highlights is something that takes careful planning, but can be absolutely stunning when done right. When it comes to using fog and haze on stage, this article will guide you through the differences, when to use each, and the other considerations that go into each atmospheric effect. First, let’s clarify what the differences are between the main types of effects.
What is the Difference Between Fog and Haze?
The main differences between theatrical fog and haze are in transparency and hang time. Fog effects are thick with a short hang time, often used to hide something with a burst of smoke. Haze is almost transparent and hangs for a long time, typically used to make beams of light visible in air.
Another way to think about the differences between fog and haze are in their natural outdoor counterparts. Haze is what you see when you look out on the distance and see that a hill or mountain a few miles away is blurry. Fog is what you see when you are driving and your visibility becomes limited so the road ahead becomes hard or impossible to see.
Do you need a different machine for each?
Because Fog and Haze are created differently, you typically need a separate machine to achieve each effect. Fog machines output large quantities of fog quickly into a small area, and typically use liquid that dissipates relatively quickly. Haze machines on the other hand will look like they are outputting more of a mist up close, and have a fan to spread the suspended particles throughout the space.
Although you should use different machines, I have created a haze effect using a fog machine in a very particular instance where the goal was to create an extremely dense cloud of fog that would naturally spread out to fill the room. To achieve this, we used a “jet fogger” which has a powerful output, and filled the machine with long lasting fog fluid. Be careful when using this method though, as it is easy to overdo it and lose sight of the actors as the cloud begins to spread. In our case, we had fans set backstage that turned on once we wanted to the cloud to disperse to fill the room.
How to Use Fog Effects on Stage
Fog is a thick atmospheric effect that generally is thick enough to limit visibility. The average hang time is under 2 minutes, meaning it dissipates completely within that time, and usually much faster. Within the category of fog there are two main types of fog effects, which are regular and low-lying fog:
Regular Fog Effects on Stage
Regular fog effects are great for hiding action on stage, or creating a plume of fog for effect. typically these machines will be stored in the wings, and fired through DMX control, or through a crew member. This fog is created with a regular fog machine, and depending on the output you need, there are different price points.
For basic effects, a $50 machine meant for halloween can be enough. Medium volume effects will run in the $150 range with around 12,000 cubic feet per minute output. High Volume machines will run higher up to about $700 for 40,000 cubic feet per minute. These machines will be enough for most theaters, but if you need ultra high volume, they can run up to $1,500.
Choosing between Water Based and Oil Based Fog
Water Based Fog
Because of its simplicity, minimal health impacts, and low relative cost, water based fog effects are the best for theater and opera. It’s simple to use and maintain, with just a pump and heating element. Water Based Fog fluid is made from a combination of water, Glycerin, Triethylene Glycol, and Propylene-Glycol. As you would expect, water is the largest percentage of the mix for water based fluids, and the exact mix of ingredients changes the hang time of the fog.
Oil Based Fog
Oil Based effects are best for use in more industrial situations and less ideal for theatrical settings due to their possible health effects, and much longer hang time. This fluid uses a food safe oil as the main ingredient instead of water which produces much smaller particle sizes when compared to water based fluid. Because of the smaller particle sizes and the inability of the oil to evaporate into the air as quickly, oil based fog tends to last the longest.
Low-Lying Fog Effects on Stage
Low-Lying fog effects are perfect for creating either a creepy look, or a mysterious look. Often low lying fog effects take light from gobos well, and can be used to change location easily or to hide other stage effects from view. Low-lying fog can be created with either fluid based effects, or dry ice based effects.
choosing between Water based and Dry Ice for low lying fog
Fluid Based Low-Lying Fog
With fluid based effects, regular water based fog is created, then cooled either with a built in cooling system, or a separate cooler. Fluid based effects are a popular method since they don’t require a daily purchase of dry ice saving time and money over dry ice. Fast dissipating or dedicated low-lying fluids are best for low-lying effects. The ideal hang time for these fluid effects is around 30-45 seconds, so the fluids dissipate as they warm enough to rise off the floor.
Dry Ice Based Fog Effects
Dry ice fog has the definite visual advantage over fluid based effects because of the way it’s created, but with the drawback of price and added safety measures. This effect is created by using hot or boiling water to quickly sublimate dry ice, creating a cloud of colder air which condenses water in the air, then sinks to the floor. Because this cloud is extremely cold, and the concentrated molecular weight of CO2 is slightly heavier than air, dry ice effects stay close to the ground and evaporate before rising. Dry Ice fog has a hang time of around 60 seconds, and automatically dissipates as it heats up.
Because of the high concentrations of CO2 released by dry ice, there are a few considerations to take into account before using dry ice. High concentrations of CO2 are dangerous in creating a possible suffocation hazard, and breathing difficulties which can lead to panic in an automatic response. I have included some safety measures for working with all fog, and specifically dry ice fog. As with anything, conduct your own research and risk assessment before committing to using dry ice.
How to Use Haze on Stage
Haze on stage is used to create visible beams of light, which brings attention to the lighting and gives it a prominent role in telling the story. With haze on stage, the beams of light can completely change the color of the air without hitting the set at all, giving interesting visuals.
Haze is created when a machine vaporizes tiny particles of liquid so they become suspended in the air. These particles are typically around 5 micrometers in size, which allows them to remain suspended in the air for hours. When these particles are in the dark they remain almost invisible, but when lit directly in front of a dark area they create an opaque layer.
There are many different types of haze fluid and similar to fog, water based and oil based are available. In general, water based will hang for less time, and oil based will hang for longer. if working on a smaller stage, water based will likely be okay, but in larger venues option for oil based will limit consumption.
Theatrical smoke health and safety considerations
With all fog and haze, there are a few short and long term health concerns to be aware of, as well as general safety concerns which require a little bit of planning to avoid. Limiting these risks is fairly easy in some settings and challenging in others. Please be sure to do your own research on local laws, regulations, and guidelines to know what is best for your setting, but this should serve as a starting point for most situations.
Allergies and chemicals
Because theatrical fog and haze fluids are chemicals that are heated to become airborne, they are chemicals which can be irritating to those exposed. Though the chemicals used today were chosen because the majority of people are unaffected by them, some people will have reactions to them. Use the AEA Guidelines on fog and haze as a good rule of thumb if not working on an equity production. Also include signs outside the venue informing patrons that fog and haze effects will be used.
Visibility
Another safety concern is visibility. Because Fog is often used to decrease visibility on purpose, this needs to be a consideration when using fog on stage while actors are moving around. If an actor is close to an edge of the stage, or another moving hazard in the fog, there needs to be a clear method for them to determine their exact position on stage. Even if in testing you feel safe, you must always make sure the actor feels comfortable acting while maintaining their safety, and make sure it is clear to them that their safety is the first priority. Purposefully bringing the actor into these safety discussions drastically improves their confidence and allows them to feel willing to voice concerns.
Smoke and Fire Detection Systems
Depending on the smoke detection system of the building, it may be required to shut off the system during a performance to eliminate false alarms. This requires a few extra steps to legally accomplish. First, the local Fire Marshall needs to be notified of the intent to bypass the alarm system. Second, someone on the crew will need to be assigned to Fire Watch. This means taking over as a human equivalent to the fire alarm. Depending on the location, they may need formal training to do this. There may be other considerations in your local area, so please research carefully and reach out to your local Fire Marshall for guidance.
CO2 Exposure from Dry Ice
The last concern to talk about here to overexposure to CO2 from dry ice. Although CO2 is created naturally by humans when we breath out, high levels of CO2 can lead to many side effects. Side effects like dizziness, difficulty breathing, and increased heart rate are immediately problematic, with suffocation possible with extreme concentrations. Though our bodies are able to detect extremely high CO2 levels in the lungs, our bodies reaction is to take another breath to purge the CO2 as if you had been holding your breath.
A bit of forethought and planning should limit the possibility of high exposure, but prolonged exposure should be avoided as much as possible. Good airflow to turn over the air after the CO2 has been released will prevent most prolonged affects. Decreasing the amount of dry ice used to achieve the desired effect and being mindful of where the highest concentrations (which lie in the fog) are going will help acute exposure issues. Be mindful of orchestra pits as they might be below stage level and accumulate fog as it sinks.
Are fog and Haze fluids compatible with any machine?
Because fog and haze fluid work so differently, they are not compatible for use in the other type of machine. Similarly, Oil based and Water Based fluids are not compatible in a machine intended for the other fluid. Matching the correct fluid to your machine will not only increase output, but ensure longevity of the machines. Using the wrong fluid can clog your machine and possibly cause a fire hazard due to overheating. Although the AEA guidelines through Ramble aren’t exhaustive, this should give a list of which fluids are compatible with which machines: Fog and Haze Study
