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spreading fog

Discussion in 'Special Effects' started by moojoe, Jul 14, 2005.

  1. moojoe

    moojoe Active Member

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    this idea makes perfect sense to me, but i figured i should ask anyway.

    im going to need to essentially coat the stage for one show in fog for a single scene, to do this, i really need fog coming out all over the stage, but due to budgets, can only get two fog machines.
    my idea for this was to run PVC piping along the stage, drill holes every foot or so, and connect a fog machine to either end. when i turn them on, it will fill the tube, and work its way out of the tube. does anyone see this as a viable solution? i know that i need to keep the piping away from the tip of the machine due to heat, but that can be worked around.
     
  2. erosing

    erosing The Royal Renaissance Man

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    The idea that we used fire extinguishers last time we needed fog comes to mind. I think we had about 4, so we used them and it was cheaper then the fog machines.
     
  3. Peter

    Peter Well-Known Member

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    Becareful about using fire extinguishers..... there are alot of regulations and saftey considerations to be considered before using them (search arround the forums for previous topics abou this).

    Do you want a layer of fog that stays low accross the stage or a wall of fog that floats up from accross the stage. Unless you cool the fog, it is going to want to rise as soon as it is out of any pipes. CO2 (dry ice fog) sinks b/c CO2 is denser then air.
     
  4. Mayhem

    Mayhem Senior Team Emeritus Premium Member

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    I strongly recommend against the use of fire extinguishers for any purpose other that extinguishing a fire.

    One thing you may need to add into your system is a couple of fans. Depending on how big your stage is and the length of the tubes as you may find the smoke leaves the tubes before it reaches the middle.

    I have used some 4” computer fans before with fairly good effect in spreading smoke. I made up some small boxes so that a short length of 4” tube can be joined to a second length using the box. The only draw back is that the fans do not last too long as they foul up from the smoke.

    The other way is to introduce the airflow without running the smoke through it. This can be done by using a “Y” connector. These connectors are essentially a straight section of pipe with a second section introduced at an angle. A bit like this:

    ____/____ only the angle is more acute.

    This then allows air to be introduced in the same direction as the smoke will flow and doesn’t give the same problem of fouling up the fan.

    You can also make the Y section out of metal and use a heat gun to make smoke rise quickly if needed.
     
  5. moojoe

    moojoe Active Member

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    it doesnt need to be low lying, i actually want to fill the entire stage with it. the fan idea is a good idea.

    and i would never use fire extinguishers, not only is that dangerous, its just...theres a lot of things wrong with that.
     
  6. Eboy87

    Eboy87 Well-Known Member

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    At my theater, before my time, they did Little Shop of Horrors. They did an effect similer. I believe they had two smoke machines on either side of the stage, and they hooked fans into the dimmers, controlled by the scenemasters on the board, to move the smoke where they wanted. From what I understand, it worked really well.
     
  7. LDSFX

    LDSFX Member

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    I have done this effect for several shows, the most recent being Les Miserables 2 years ago. We just used two fog machines, one SL and the other SR. If they both have enough power (like a LeMaitre G300) and you turn them up at full power at the same time, they will more-than-adequately fill your stage.
     
    gbirdsall and (deleted member) like this.
  8. foeglass

    foeglass Member

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    Our school wanted to fill the whole stage with fog and came up with the idea of using theair ducts. These are usually a source of many problems in dealing with haze, but we ended up using it to our advantage by hooking up a hazer inside the actual air duct on the side of the stage.
    ___________
    |----------------|
    |__(hazer)__|

    ^^^^^^
    the hazer sat inside this air duct


    Because it was a hazer, it was much lighter and floated well above the stage so we had to direct with our best friends duct tape and cardboard, but with a fog machine this problem should be eliminated.
     
  9. The_Guest

    The_Guest Senior Team Emeritus Premium Member

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    Have you considered experimenting with a low level liquid-nitrogen system? It's amazing how easy it is to manipulate and eliminates the hassles of dry ice. Sounds like dry ice or liquid-nitro would be you're best option, because the typical fogger isn't going to coat the stage like you like. Foggers typical tend to be ambient, because that essentially what fog is. Theater often requires you to exagerate to convince your audience. So, sometimes a mildly/cloudy room isn't enough. I always like a thick low-level fog combined with a light and ambient atmospheric fog (haze even works sometimes) because it makes it obvious that it's foggy but doesn't cloud up the acting space making it hard for the audience to understand the actors visually/physically. Also a foggy background combined with these things can help, but it's very tricky and hard to pull off. I'm not much of a fog expert anyways.

    So it'd sugguest experimenting with different fluids, that is if your machine permits it. So contacting the manufacture of your machines would probably help. LeMaitre, Gem, etc should offer you different methods and fluids to help you get results.

    [​IMG]

    [​IMG]

    The system used here creates a thick low level fog by dispersing lidquid nitrogen. In this particularly picture it's been used for a production of Fiddler on the Roof. For those of you who are familar with the show, it was used in the "Dream Scene" when Frumah Sara returns from the dead to haunt Tevye and his wife. Anyways, the outputs of the system are attached to a ventilation system that is routed allover the interior of the set to a series of hidden vents throughout the exterior of the set. When this system is activated it will completely cover the downstage area in front of the set with a thick low fog no taller than a yard. Once the downstage area is covered the fog will float its way off the stage, falling into the house and orchestra pit.

    Even if you don't have a set to hide pipes or ventilation hoses (like the ones hooked up to the output of a dryer), you can still route them around the acting area. You could even route it throw the acting area, provided that you'd make the vents/pipes/hoses visually friendly from an audience perspective.
     
  10. Dale

    Dale Member

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    Thaty's funny. I always wondered if that would work. Just never had the time to do it really.
     
  11. MSwan

    MSwan Member

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    Be VERY careful putting any kind of smoke or haze machine in ventilation systems, many buildings have smoke detectors in the ventilation system and no one wants the fire dept showing up in the middle of a show. It is also more likely that the effect will spread to an adjacent room which if you have had th fire dept disable the theatre zone of the fire alarm the adjacent room may not be part of that zone.

    As far as spreading atmospheric effects over a stage most of the time a machine on each side with a box fan (hooked to a non-dim circuit of course) will do the trick. If you want to have the effect come from the whole width of the stage then you can use the same kind of pipe that is used for stove vents and the such (about 3" metal duct) then cut slits along the length. You can then put this duct US (perhaps build it into a ground row to hide it), or you can build it into the DS edge of a raised platform stage (like a temp rake stage). It will proably not come out as thick mid-stage as the sides but if you have 2 strong machines it should work out well. If you ues metal ducting you can also put the duct right against the machine as there is almost no risk of it melting or catching fire. Keep in mind that fluid will build up in the duct over time, so be careful when loading out.
     
  12. Peter

    Peter Well-Known Member

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    I believe the reason you are supposto leave space at the end of the machine is so that the gases coming out of the fog machine can mix with more air and create a larger volume of smoke. There are ALOT of websites out there about creating smoke effects, take a whirl at searching for haloween smoke stuff too, b/c there is a large set of people who use smoke machines in elaborate haloween displays.
     
  13. MHSTech

    MHSTech Active Member

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    If you have a relatively small stage just place your machines in the center of your stage, in and/or around your set. It will spread throughout the whole stage.

    Mayhem has a really good idea with the Y-connector (sometimes called a "Wye") Here is a picture of one. http://www1.mscdirect.com/ProductImages/3700187-11.jpg
    If you decide to use tubing to spread the fog, take a look at dust collection tubing and fittings. They may be cheaper because they are thiner than PVC.
     
  14. Inaki2

    Inaki2 Active Member

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    Ha! I tripped the fire alarms for Full Sail Live during Haloween, and they were in test mode!
    There was a looooot of smoke!
     
  15. Mayhem

    Mayhem Senior Team Emeritus Premium Member

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    Yep - that's the thing I had trouble describing! Thanks MHSTech for taking the trouble to find a picture.
     
  16. Radman

    Radman Well-Known Member

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    Time to bring this back alive.

    I am working on Beauty and the Beast right now for school, and I really want a LOT of fog effects. They just fit in everywhere! I want to be able to go from some atmosphere to complete white out on parts of the stage in a matter of seconds. I want to put fans on dimmers and blow the fog around. What is the best way to do that? I am particularly attracted to ways that are under $1k for the expendibles/machines. I would then add what few more machines I can borrow. All the free machines in town are either broken or sold. The stage is probably 50' wide and 20-25' proscenium with maybe 50-60' to the ceiling.
     

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