Fun with Fog Generators

BoomZilla writes "Only 10 or so shopping days to Halloween. If you're at a loss for a project this weekend check out gotfog.com for a full set of detailed instructions on the construction of a Fog chiller. "What's a fog chiller?" you may ask. And rightly so. Let me explain. A fog machine dumps fog juice on a heating plate to produce oodles of the white, floaty stuff. Problem is that it doesn't hug the ground like you see in the movies. An alternative that is employed to create the ground-hugging variety of fog is a dry ice machine (which heats up dry ice and disperses the resultant cloud of fog). The problem is that dry ice is (a) expensive and (b) not always that easy to get. Enter the fog chiller. The chiller can be built very inexpensively (major cost is the sacrifice of a largish cooler) and works with a regular fog machine that consumes low-cost fog juice. Go on, give it a try. You know you want to. And just imagine the look on the faces of your little ghouls and ghosts come the 31st when your house looks like boot hill on steroids."

Re:Dry Ice Fog

[ShinmaWa]

• Firstly, dry ice is certainly NOT expensive. Prices usually fall in the $0.50 to $1.00 / lb range
• 25lb load will only last about 10 minutes

That sounds pretty expensive to me. At $0.50 to $1.00 per pound, the hourly cost to fog an area is $75 to $150. Using your figures, a basic 4-hour halloween evening of fog effects could run upwards of $600!

It might be that a pound of dry ice is inexpensive, but if its used up in only 25 seconds, it adds up quick.

Dry Ice V. Chillers

[cybergibbons]

Most of this discussion seems to have veered off onto how cheaply you can get dry ice. Over here in the UK it is used rarely for theatrical effects, for many reasons.

It's awkward to store, and will sublime even in a freezer. The room you store it in needs to be ventilated or dangerous levels of C02 can build up.

It's hard to control. Most people just pour hot water onto it. There are some better commercial devices that heat water or whatever, but it is hard to turn the fog on and off.

It stays for a long time. Quite often people want the low lying fog to go before the next scene. Dry ice based fog remains for a long time.

Fog chillers however don't have these problems. Yes, the fluid for them costs a fair bit (up to £60 for 5 litres), but you can control the flow, density, and type of fog. Some machines will do chilled fog, smoke, and haze (very low level smoke, used to show beams of light). You can sit at the other end of the room and control it remotely using DMX. It disperses very quickly as well, so when you kill the machine, the fog is gone very very quickly.

Saying this, there are now machines that use C02 cylinders which solve a lot of the problems of solid dry ice.

Dry ice is also better for on stage effects (witches cauldron) and practical jokes. We tipped a lot of C02 pellets down a toilet once, and found it quite funny when all the other toilets in the block started bubbling and smoking.