How NOT to make ground-hugging fog

Poor [Todd Harrison] spent all of Saturday and Sunday trying to make some ground-hugging fog for his Halloween decor. His fog machine hack turned out to be an utter failure. But he admits it and reports that he still had a lot of fun. Don’t feel bad [Todd], this happens to everyone from time to time. And anyone that has doubts about [Todd's] skills need not look very far to find out that he does know what he’s doing.

The project started off with a theater-style fog machine. The problem is that this fills a room with a thin foggy-haze that doesn’t take shape outdoors. He wanted that ankle-deep graveyard effect and had seen several examples online that use a fog-machine with a bucked of dry ice. He though he’d just use his own bucket full of regular ice and salt water. Inside the bucket seen above there is a 15′ coil of copper tubing through which the fog machine’s output is passed. On the other side of the bucket there’s a plastic tube that goes to a sheet of plastic meant to distribute the cooled fog.

The problem here is that the fog machine puts out a hot mist. When it hits the ice bath the mist condenses into liquid form and that’s the end of the fog. As he attests in the video after the break, the dry-ice fog hack isn’t pumping out fog. It’s just using the heated steam to pump out carbon-dioxide vapor boiling off of the dry ice.

Comments

  1. Gdogg says:

    That’s a pretty funny substitute to try.

  2. vonskippy says:

    Even the best planned experiments sometimes fail.

    The process is just as important as what it produces.

  3. Vinnie Vu says:

    Works fine when I did it.

    The problem was he used copper coil, and they’re too thin. I just ran a 1.5″ PVC from the fog machine to an icebox, and filled it with ice on a crate, so that the fog flow through the ice, and exit out the bottom of the ice box as chilled fog. It stayed on the ground pretty well, works great in grassy area as the fog hang onto the grass.

    • gannondrk says:

      Came to the comments to see if someone posted the proper solution, you are a 100% correct, I made a ghetto cooler out of a coleman cooler and a hole saw. No need for the copper coils.

  4. Spacehog says:

    http://www.youtube.com/watch?v=gncp2FPnk4k seems to work w/o dry ice or the fog contacting the ice.

  5. Derf says:

    Too bad a quick search of fog coolers wasn’t done, and the . Simply looking at the construction makes the DIY solution simple. Went at this wrong, got the right idea that you chill the fog, but even stated the proper method while detailing how this model fails. Also, didn’t really understand how the box cooler works, it’s not the same as dunking dry ice in water.

  6. mstone says:

    I used to be a stagehand, and have done lots of fog effects.

    Using chilled fogger mist to make a dense, floor hugging cloud was a traditional “prank the newbie” trick/object-lesson where I came from.

    It lays in beautifully.. I’ve seen guys build a layer 2″ deep so dense that you couldn’t see the floor.

    .. then it warms up.

    Machine fog is actually a particulate of nontoxic, high molecular weight alcohols. The particles don’t evaporate, they just hang around until they come into contact with a suface and adhere to that. The average fog effect uses maybe a teaspoon of fluid to fog a whole theatre, so there isn’t any noticeable mess.

    Chilled machine fog only stays near the floor as long as the air around it is cold. As the air warms up, it rises and mixes into the air above it.. and so does the fog. That beautiful 2″ thick layer turns into a London pea-souper within about ten minutes.

    The more experienced stagehands usually arrange for the new guy to do that during a rehearsal, but I have seen it happen in performance. On one memorable occasion, the cutain opened and the ground fog flowed right off the stage and into the orchestra pit, which remained a seething cauldron of music for the rest of the night.

    Chilled machine fog is works well for thin ground layers, but for the really thick stuff, CO2 is best.

    • andarb says:

      ROFL @ Seething cauldron of music

      I know it is a teaching tool to remind neophytes what not to do (and funny) but why must we prank the new guy. He’s probably nervous enough as it is. :p

      • Derf says:

        why prank the new guy? Often to see how they react. Fog going bad isn’t all that important, but how they handle it is an indicator if they keep a cool head, or spin out of control. Important to know in case something more important happens, then you know what you will have on your hands.

      • mstone says:

        In many cases, the best way to learn how things can go wrong is by seeing them go wrong. Hearing about it is one thing, having a “then this happened” story sticks better and lasts longer.

        The ‘pranks’ are chosen to give newcomers a taste of things going wrong in a context where nothing really bad happens. They’re bonding experiences more than cruel jokes because the follow-up is for all the elders to stand around trading “when that happened to me” stories. It’s a rite of passage that brings the newcomer into the club of people who’ve gotten it wrong and lived to tell the tale.

        The ones that are planned happen in rehearsals because ‘things going wrong’ is the ground state of rehearsal. The actual cost of a fog effect going bad during rehearsal is that everyone gets about ten minutes of break while the fans clear the air, the lighting people play with the cues to see what cool light-through-the-mist effects they can get, and the stagehand who did it gets attention from the women (or men) in the cast.

        And yes, anyone who wants to make a living backstage has to get used to things going wrong. Watch the movies “Enter Laughing” and “This Is Spinal Tap” with anyone who works the stage and they’ll tell you that those are documentaries. All good stagehands learn to improvise at speed, and all good performers learn to be gracious when something sticks, falls, happens when it shouldn’t, or doesn’t happen when it should.

      • mstone says:

        OBTW – the ‘orchestra pit’ thing wasn’t done by a new guy. That was a roadie determined to show us ig’nant local guys he knew more about foggers than all of us put together.

  7. Alex Rossie says:

    Ice + Salt can get you to like -20°C which is colder than I expected.

    Dry ice is at -77°C so pretty big difference.

  8. Emerica says:

    I’ve been working on the same deal with a garbage can and 25′ of alum dryer ducting.
    Working pretty well, using two foggers.1000w and a 400w
    Have about 2′ from foggers to the can. About 10′ makes a run through the flower bed which feeds 3 cardboard coffins.
    The problem I’m facing is getting it the fog cold enough in the ambient temp to stay low.
    Weather network saying its going to be around 0C.
    The effect tends to work best about 10C.
    Either way I’ll have a foggy yard, just not sure I’m going to get the effect I was hoping for.

  9. Chris Muncy says:

    We once built a dry ice fogger out of a 55 gallon drum, 110v water heater element, and a squirrel cage blower.
    You get the required fittings for the heater element and install it a few inches from teh bottom of the drum. About 2/3 of the way up you need a shelf for the dry ice. old steel rack, just something to hold the dry ice while it is sitting in the water. The squirrel cage was used to blow air into the top of the drum and out a 4 inch hole where rv type sewer hose was used to pipe the fog where you needed it.

    WOrked great. Took about an hour to get everything up to temp. The only downside is that you can overfill it with the dry ice and the water won’t get hot enough to create the fog.

    Cheap and easy solution.

    • Jesse says:

      This is what’s known as an aquafogger. We use them all the time for ballets at the theater I work at. Gives that nice low lying cloudy fog look. whats great is the fog dissapates before it rises so the room doesnt get filled up.

      • M4CGYV3R says:

        Isn’t an Aquafogger just a big tank of heated water with some pumps? I think that’s what we used at a local theater for fog many years ago, and all you do is put a bunch of dry ice pellets in it and hit a switch. Bam, awesome ground fog(and puddles, lots of puddles).

    • Jesse says:

      I would like to make a few corrections because there is a little bit of misinformation peppered throughout this post.

      First, that is a standard consumer grade fog machine. The same as you can get at party city for halloween, but just marketed for DJ’s. Its a cheaply made fog machine with a slightly high price tag just because it carries the Antari name. I have the same one in fact I use as a spare.

      Fog machines used in theaters are almost always hazers, which are just low output fog machines with a blower fan to disperse the fog. These are specifically to give a hazy look, and to show lasers and beamage.

      Any fog machine worth its salt is DMX controlable, variable output, continuous output at 50% or more, and will generally run you $800-$3000. Other important traits are high output capacity, low fluid shutoff and the built in ability to be flown on a rig. Specific manufacturers of the best fog machines are Martin (pro versions), Rosco, Antari (pro versions), High End Systems. The worst ones are American DJ, Chauvet, and Party City or any other store brand.

      Finally, the fog machine is actually producing the fog in the home made fog chillers out there, you can use either plain ice or dry ice. Dry ice is usually preffered because it gives a slightly denser, longer lasting low lying fog, and does not leave behind big puddles of water to mop up or drain away.

      • M4CGYV3R says:

        Even this small fogger from Antari is pretty solid – it’s just lower output.

        I have also used one of the massive 1800-watt Chauvet foggers with great luck, but their smaller ones are garbage. Rosco is still the best I have worked with, but they are quite expensive and require very specific fluid and care, which is a lot of work for some people.

  10. nah! says:

    now make a distiller and enjoy jour schnaps

  11. Thomas says:

    Dry ice doesn’t boil. It sublimates.

  12. Alex Rossie says:

    Just thought I’d add, we’re getting a lot of ice/salt challenge girls in A&E lately.

    They cover their arm in salt then put an ice cube on it, the result is nasty frostbite of varying degrees. The numbing cold hides the agony until the skin defrosts (YES DEFROSTS!!) and people say men do the stupidest things…

    It’s a great teaching point on why frozen steaks are awful.

  13. Jarrod says:

    “I have not failed. I’ve just found 10,000 ways that won’t work.” – Thomas Edison.

    Even failure has it’s merits, knowing what doesn’t work usually helps in working out what does in my experience.

  14. soopergooman says:

    look at all those meters and osciliscopes on the wall behind him. dang well stocked.

  15. parkolay says:

    store in non-volatile memory;
    PV=NRT

  16. Carnal Form says:

    The easiest way would have been to put ultrasonic transducers in the water.

  17. Will says:

    He took the nozzle off I bet that is why its not working. Without the nozzle to block the flow the fog juice goes through the heating block too fast. Also, it needs the nozzle to atomize the liquid.

    I think Emerica has it right >> Dryer Duct

  18. tech123 says:

    Lol. I would never post something like that

  19. I got him sorted in the youtube comments. he had just removed the most critical part, the atomizer nozzle. Once he put that back on, and stopped running it through such narrow tubing then it all worked out. Maybe he’ll make another video when he gets the chiller finalized. I thought maybe he could use a shopvac as they usually have a bucket, then he could pipe the inlet to go down into the cold dry ice, who knows. But it would be a quick experiment, since shop vacs are everywhere.

  20. I think this is the result of a HaD editor, not the OP. I don’t even know if the OP is aware it made HaD, he was just making it for his kids and posted a video since he frequently does diy videos. At least that’s what I gathered.

    The technique *does* work because it’s not steam, it’s glycol vapor… see here: http://www.youtube.com/watch?v=_MB3CQL5PYM

  21. M4CGYV3R says:

    That’s funny. First, he removes the atomizer so it doesn’t really create ‘fog’ in the first place. Then, he runs it through a small tube which then contains 100% fog fluid vapor which just condenses back to pure fluid. A nice distilling operation, I’m sure.

    The best system I have ever seen was done with dryer hose around the outside shroud from a fog machine, and it merges with another input hose in a Y-shape, and finally vents out the single hose side of the Y.

    Coming into the second input of the Y hose was air which was blown through a cooler full of dry ice, thereby mixing the cold air/CO2 with the fog after the cooler. It saved a ton of life on the dry ice, and didn’t create the usual huge puddle of oily fog juice in front of the output hose.

  22. EdgarVice says:

    That happens when someone is doing just try and error and doesn’t understand physics… Imagine the one is working in an nuclear power plant.

  23. bgsteiner says:

    I work in the theatre business as a lighting and effects designer and i can tell you the way our foggers work is the heater heats a bottle that creates the gas then it flows through an ice chamber not through a tube or anything though then is allowed to flow out through an open hole about 1″x3″ its all free flowing as no spray nozzle is needed

  24. PaulyPaul says:

    You need to let the fog expand before chilling it. Then once it is fog, it will get cold thru the chiller and the output will hug the floor. Try using dryer vent hosting. Worked for me.

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