The fog chillers currently on instructables are a variation of the "fog on the rocks" design, but have a few shortcomings that small changes can correct.
For less money we can construct a re-useable fog chiller that will cool more fog, requires less ice, allows for more fog to be produced, and is considerably easier to assemble.
If you're looking to build a fog chiller, this is the one you should build.
Step 1: Justification, Design Changes, Theory, and a Few Little Tips for Avid Chiller Designfolk.
The othertwo are examples of the "fog on the rocks" design that has been popular with home haunters since 1995.
The "Super Cheap and Easy Fog Chiller" doesn't produce a lot of contact time between the fog and the cold, resulting in less cooling. I imagine that a great portion of the fog simply blows clean through, the second design forcing the fog to sink is a better one.
The Fog Chiller for $10 blasts the fog directly into the wall of the cooler box, this is bad, more on this in two paragraphs.
Both of the other two chillers use styrofoam cooling chests as their chilling box. This is a rather bad plan for a simple reason, the fog eats into it and becomes toxic. The chillers are not exactly reuseable, your fog becomes toxic, and I hate the squeaky sounds styrofoam makes.
So, changes? The important one is the "fog cage". This is a gap between the nozzle of the fog machine, and the chiller. This is important because for the fog to form properly, optimally, and in maximum abundance it must mix with a LOT of air immediately. If it comes into contact with a solid object, or is in an air starved environment you end up with less fog. Less fog means you need more fluid and and a more powerful machine. Costs go up, way up. The change in the amount produced through the use of a fog cage is very dramatic. Those who have already built the styrofoam chillers should give pointing their fog machine into their chiller from a distance so that they can get the benefits of the extra fog without the extra work of making an extra chiller.
Second change is simply switching from a styrofoam chiller to a regular ol' plastic tub. It doesn't react with the fog, it's tougher, and you can store some of your halloween stuff it when the day is done. You may think the ice would melt faster, but the primary source of heat isn't ambient, it's the really really hot fog you're blowing in one end of your chiller (duh). Also, in my tests the chiller in the photos keeps the ice for about 7 hours of use with an automatically cycling fog machine.
Step 2: Materials and Tools
1 38L (10 gal) storage tub - $4.50
2' Chicken wire (or hardware cloth) - $0.86/foot
2 PVC couplings - $0.99/ea @ building supply store
Glue gun and glue
Step 3: Chicken (wire) Chop
What you want in the end is a rectangle vaguely the size of the top.
Take the chicken wire, and put it aside for now, you'll need it in just a second.
Step 4: Ice Tray Feet
The feet I like the best are rolled pieces of chicken wire. The materials are already there, they fit well, and the holes guarantee proper airflow.
The easiest way to make wire feet is to roll them around something, and be careful not to gash your finger open.
Make sure the feet are all mostly the same height. Exact isn't too important.
Step 5: Think, Measure, Think, Measure Again, Cut.
Next, take the other coupling and measure a circle near the top of the box. Line up the top hole so that the opening faces into the box the long way. Remember you want the fog to touch as little as possible for as long as possible to allow for maximum mixing with air, and maximum fog production.
Cut out your marked circles, remember cut inside the lines to stop from cutting too much. Another tip, a hot soldering iron is extremely practical to cut through thin plastic. Just don't breathe in.
Insert the couplings, and try to keep them as flush on the inside as possible.
Lastly, seal up the holes with hot glue. Sealing from the outside, and then from the inside makes the process much simpler.
I know, this step is almost too documented in relation to the others. But I figured this one was easiest to show through photos.
Step 6: Drain Holes (optional)
Don't do what I did and place the first holes in a part that's raised, because it won't collect water (oops).
Step 7: Assemble
When you go to store it you can just fold the flaps the rest of the way over and store them pointy bits down, allowing it all to pack flat.
Step 8: Finishing Touches
Toss in some ice, throw on the lid, heat up the fog machine.
Step 9: Eat Some Stewed Brains
Step 10: Action!
Here it is in action, lower, thicker, and all around better fog.
Note that it was very windy, and very bright, and the fog is still very visible, and hung out for a good long while.
Step 11: Bonus Mini Instructable!
Instead, we use our soldering gun to carve them into the ever handy skull chips! Handy for what? Nothing of course!