If you’ve ever ridden latest iteration of the Pirates of the Caribbean ride at Disneyland, you will remember how, right before you hit the first drop, you are greeted with the ghostly image of the tentacle-faced Davey Jones creature warning you that “dead men tell no tales”. I certainly did.
The effect uses rear-projection video, shined onto a screen of water vapor created by ultasonic atomization, that is sandwiched between 2 laminar airflows, which keep the sheet of fog contained. The commercial Fog Screen that spits out this screen costs tens of thousands of dollars for the small one.
I attempted to create my own cheap version of this system using a wooden box, a window fan, some drinking straws, and a cheap fog machine. I almost succeeded.
The original idea was to mimic the commercial unit, and sandwich the fog between 2 sheets of air. Unfortunately, I had problems delivering the fog to the center chamber of the box. As I was building this rig as an effect for a haunted house, Halloween crept up on me and I ran out of tinkering time, so I just decided to block off one side of the box and pump the fog and the air together into the chamber, letting it exit together out of just one of the vents. This actually worked out fairly well, but I do plan to work out the bugs for a future version. I think that if the fog and “plain” air are sandwiched, the screen will remain coherent for quite a bit longer, and make for a much nicer screen effect.
I have no idea how the commercial fog screen makes those glass-smooth sheets of air, but all I could think of was to shoot the air through some drinking straws. I made a little box-jig and hot-glued up some bricks of 2 inch straw sections. I then chained those bricks together into long vents. It does straighten out the airflow quite a bit, but certainly does not produce a laminar flow. Oh well.
One thing to consider whenever you are using a glycol fogger, as this design does, is that these units use a heating element and a high-pressure pump to create the fog, which comes out hot and therefore rises, filling the room, or drifting away into the night. In order to keep the fog dense, and clinging eerily to the ground, you will want to employ a fog chiller.
I made my fog chiller with a 25 foot length of dryer duct coiled inside a garbage can. The garbage can is filled with ice, and the fog chills out while making its way through the pipe. The fogger sits on top of the garbage can lid and enters the chiller through the curved upper pipe.
The biggest hangup with this rig, was the intermittent nature of the fog. Cheap glycol foggers will only spit out fog for about 20 seconds at a time before pausing to reaheat before the next burst. Mine is off more than it is on.
Thoughts on further development:
This year, I showed Mark Gervais’s “The Eye” animation on the fog. Next Halloween I think that I will show a live feed of my green-lit self on a black background, that way I can talk to the trick-or-treaters from the fog.
Here are some more build photos.