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Haze and Fog Machines
Equipment Reviews

The use of smoke, fog or haze machines has long been accepted as the best way of maximising your lighting effects as without the air borne partials the moving beams of light are not visible, this was fine back in the 70s and 80s when we were all using screens and spot boxes however almost all modern effects lighting relies on patterns of beams whether high powered lasers, intelligent moving head units, wiggly mirror effects or moonflowers.

 There are generally 2 common ways in which fog effects are produce in stage productions and disco applications. One method is to use equipment that utilises the properties of  “dry ice” however the more practical and popular option is to use a fog machine that uses a specially manufactured water based fog fluid or fog juice, these are often referred to as smoke machines as the effect often looks like smoke however these machines do create liquid droplets as in fog not smoke which is made up of dry particles. I personally prefer to call them fog machines as this is less likely to cause offence to your punters or objections to its use.

 Effects lighting with fog-         

 The basic operation of a fog machine is reasonably simple the fog fluid or juice is heated to create fog or haze. When you overheat cooking oil on the cooker in your kitchen this can create a lot of smoke and this is the basic principal of how a fog machine works. Fog machines use a fluid sometimes referred to as fog juice that is pumped into a thermostatically temperature controlled heat exchanger that vaporizes the fluid into thick clouds of fog. The fluid or juice is a mixture of pharmaceutical grade propylene glycol, triethylene glycol and distilled water that is mixed by the manufacturer in a consistency specifically designed for their own machines. It is therefore definitely not a DIY job, never attempt to mixing or blend juice yourself. It is strongly advised that you use only the fluids recommended by the machines manufacturer and never substitute this with cheaper fluids as this will certainly void the machine's warranty and could damage some of the components such as the heat exchanger or pump. Never add scented aroma based solutions unless they are specifically designed for your fog machine, as you don't know how the added chemicals will affect people in a vaporised form. If the wrong fluid is used it is possible that unpleasant and toxic fumes including formaldehyde could be produced. Please take note of this as I know from experience having had to evacuate a room due to pungent fumes that resulted in some guests vomiting after an assistant put the wrong fluid in one of my haze machines! With most DJ marketed fluids the smoke produced tends to diffuse relatively quickly however some manufacturers such as Jem (AKA Martin Manufacturing) now produce differing grades of fluid for their machines from “Regular DJ” fluid with a relatively fast dispersion to ZR Juice and “Pro fluid” with medium or longer lasting dispersion times.

All fog machines require a warm up period when switched on generally around five minutes. The difference between budget consumer and high-end professional models is that budget and semi-professional models usually cannot sustain a continuous output of fog. That is that they will usually generate fog for a short period then need to pause to reheat before they can make fog again. This is generally a continual automatic cycle during their operation. More expensive models can generate fog continuously without the reheat cycle in between, but these can cost much more than budget or even semi-professional models. The wattage (power rating) of the heating element in the machine can be a good indicator of how well a fog machine will perform. Most budget fog machines generally range from 400 to 1300 watts. With a higher wattage rating the fog machine can not only produce more fog but equally as important it will not have to go into a re-heat cycle as often because the heat exchanger has more power available.

Most fog machines come with some type of remote control either in the form of a simple single push button on the budget machines. Better machines generally have a remote timer controller that has a fog volume control, operation duration timer and rest duration timer, that is these better remote controls allow you to set the intervals at which the fog machine will come on, how long that interval will last and the volume or thickness of fog produced. Fog machines make some noise while then they operate usually produced by the pump as fluid is pumped from the reservoir to the heat exchanger. The fog expanding out of the nozzle can also produce enough sound to make a person jump in higher performance machines this is obviously undesirable in some applications therefore care must be taken when choosing a new machine.

Whether cleaning of fog machines is necessary varies between manufacturers and instruction manuals must be followed. Some manufacturers advise you to empty the fog fluid tank before storing the machine for longer periods; this is where a removable container comes in useful. With other machines it is unwise to run them dry to remove the fluid remaining in the system as this fluid acts as a lubricant for the moving parts, however some manufacturers recommend that before putting your fog machine into storage you need to clean it out thoroughly by running distilled water through the system to flush out the remaining fog fluid; therefore always study and follow the manufacturers instructions as a well maintained fog machine using the manufacturers recommended fluid should provide years of reliable service. One of the main causes of burned out pump-motors is running the fog machine dry of fluid when the reservoir becomes empty or the machine becomes clogged. Many better machines now have protection against this. In the event of a part failing such as the pump most retailers are unable to offer a prompt repair service. It is best to be sent the failed machine back to the relevant manufacturers service department. However on inexpensive imported machines this is impractical and by the time you pay carriage labour and parts it will cost as much to repair as buying a new machine.

DRY ICE-
The alternative method of producing thick fog is by the use of “dry ice”, this is generally available form ice manufacturing plants and is relatively inexpensive to purchase however dry ice is most difficult and dangerous to handle, transport and store. Great care is required to avoid contact with unprotected human skin or tissue, heavy protective gloves need to be worn at all times. You also need to ensure the area the dry ice is used, stored and transported in is very well ventilated, a bit of a challenge for transportation! The dry ice vapour is heavier than air and it can therefore concentrate in low areas or enclosed spaces like a car, a van or a room.

To produce the required effect the dry ice is placed into a reasonably simple machine similar to a giant kettle in principle. The top of the kettle is sealed, with exception of an exit spout to which a large hose vent hose can usually be attached. When the basket containing the dry ice is lowered into the water, the dry ice sublimes, and a thick, white carbon dioxide fog is formed. This fog is heavier than air so it tends to hug the ground as it comes out of the hose. Dry ice is basically frozen carbon dioxide and has a surface temperature of -109.3 degrees Fahrenheit (-78.5 degrees C). Dry ice has the very nice feature of “sublimation” that is as it breaks down it turns directly into carbon dioxide gas rather than a liquid. The super-cold temperature and the sublimation feature make dry ice great for refrigeration. For example, if you want to send something frozen across the country, you can pack it in dry ice. It will be frozen when it reaches its destination, and there will be no messy liquid left over like you would have with normal ice.

We have all seen the dry ice fog effect used on Top of the Pops or old horror movies when the fog clings to the ground of a spooky cemetery scene. There are expensive “heavy fog machines” now produced by some manufacturers that mimic the traditional dry ice effect, these heavy fog machines use a refrigerator compressor to chill the air and fog mix before it bellows out of the machine, this modern equivalent of the dry ice machine is now the method that is generally used in West End stage productions, films and TV due to the ease of handling of the raw materials.

Popular model of dry ice machine is the “Le Maitre” “Pea Souper”-


No published research has been made as to whether fog produced by Glycol/water based fluids has any side effects on people's lungs. It is generally accepted that sometimes the fog produced can cause problem for asthmatics however nothing has been proven conclusively and due to the nature as asthma it is possible that symptoms could be psychosomatic, however if your customers are not happy with it, play safe and switch it off! Modern effects lighting requires a light haze to bring the lighting beams to life and produce desirable mid air beam effects so it’s a major disappointment if you are unable to use your machine. I have found that one successful way of minimising complaints from gests at your gigs is to point he machine at a rear wall rather than face it forwards onto the dance floor, a useful tip is to take along a oscillating desk small fan to spread the haze throughout your light show and minimise the attention that a jet of fog into the room may produce. Most manufacturers now produce Hazers, which combine a low output auto cycling fog machine with a small chamber containing a fan, this produces much the same effect and is far less obtrusive to your guests.

The particles produced by fog machines will set off ionisation type smoke detectors. Generally this is only a problem with ionisation or optical type detectors as they sense the fog particles as smoke. It is therefore wise to check that the use of fog or haze is acceptable by venue management and that their fire alarm system is compatible with them. You should never attempt to disable smoke detectors by gaffa taping them up or unplugging them from their sockets as this would be a foolish and dangerous route to take resulting in serious litigation by the authorities if you are caught or there really is a fire. Sprinkler systems are usually triggered by heat therefore fog will not active these.

If you use a lot of fog you will get a very thin film of fog fluid residue on everything in the room, it shouldn't do any damage but feels sticky to the touch, the desk fan as suggested earlier will certainly require regular cleaning and some venues will object to the use of fog on these grounds alone. Most experienced mobile DJs will have horror stories about the arrival of the fire brigade due to an accidental triggering of a fire alarm, I can recall a silly mistake made in a very up market hotel I was performing in near Stratford upon Avon about 10 years ago, the hotel was full of rich Americans and Japanese. Before becoming a hotel in the late 70s this previously derelict country mansion was ironically used as a set in numerous Hammer Horror movies. For this very exclusive wedding that I was performing at I was set up in an oak panelled room that was normally used as a library and sitting room. I had checked if it was ok to use fog with the duty manager when setting up. She got it wrong! I invited the bride and groom onto the floor for their first dance and let off a small spurt of fog to bring the mirror balls to life, as I watched the fog rising into the light show and the pretty reflected fingers of light off the mirror ball; I spotted a detector on the ceiling directly above the mirror ball, why had I not noticed it before? To late, all hell broke lose as the very efficient fire alarm system came to life with a loud wale of sirens! Right time to own up and run the short distance to reception! A very angry looking chef was shouting at the duty manager and other staff were rushing around trying to locate the zone that had triggered the alarm. I explained quietly what had happened and that it was a false alarm that no one should be concerned, the general manager now took charge and told me that the whole hotel had to be evacuated and everyone must assemble in the car park as it was policy and the fire brigade were on their way! I asked them to ring and cancel however I was informed that the alarm was linked directly with the station in Stratford and it was too late. There were 4 fire engines there within 5 minutes! How embarrassing! All my fault! The management were very cool about the incident saying that it was a useful exercise for them and it was also good to now how quick the fire brigade was. The General Manager advised me however to stay away from the head chef as he was very angry as the fire alarm activation had shut off the gas main in the kitchen and many expensive a-la-cart meals had been ruined. The up side of this event was that I learned a valuable lesson and as a bonus my client tipped me £50.00 as the fire brigades presence had produced a wonderful photo opportunity for them and their guests!

On a more serious note it is now worth noting that in this litigations age we now work in that most public liability (PLI) insurance policies available prohibit the use of fog, haze and smoke effects. I can only assume that this is justified by the insurance companies on the grounds of fog limiting visibility and increasing the risk of falling over objects obscured from the sight of punters.

Finally to finish on a humorous note I recall being called to a new nightclub just a few months after I had completed an extensive sound and lighting equipment installation. We had fitted a high specification club fog generator in a specially constructed cradle above the DJ booth. The club owner had complained that his expensive new machine was not operating. On investigation I was confused by the smell and consistency of the fog fluid in the reservoir, I quizzed the regular DJ who had conveniently called in about who had put the fluid in, after a short discussion with another of his DJ colleagues it appeared that another of the DJs had been caught short on the regular guys night off and had emptied his bladder into an empty plastic gallon container found on the floor of the DJ booth. The next night the regular DJ picked it up and put it into the smoke machine and proceeded to spray vaporised pee over the unsuspecting audience!

R. Mark Weller- Ocsid Entertainment Solutions (NADJ Wales)

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