# Fog setup for a first timer



## Mattbhm (Oct 1, 2019)

Hello everyone!

So we're going to do our first major Halloween scene this year and decided fog would be a good addition. We're going for a graveyard scene so we're looking for thick ground fog.

I'm on a budget so I grabbed the ADJ VF1300 for $95. I am under the impression that a 400-700w wouldn't be enough to do what I'm hoping to do.

My plan is to use Froggy's Bog Fog. I need a chiller of sorts to keep the fog low and I was looking at this one. https://www.instructables.com/id/The-Ultimate-budget-8.20-Fog-Chiller/

Should that work well? It will be outdoors, and I do know that any wind will really mess it up.

Thanks for any help!!


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## stick (Jan 21, 2009)

I have tried different types of fog chillers and the best one for me and was the cheapest is a one 10' section of black ADS 4-in x 10-ft Corrugated Solid Pipe with one section (or more if have space *but* may need a fan to push it) of ADS 4-in x 10-ft Corrugated Perforated Pipe. If you want you can put ice in the solid section to help cool down the fog more but I do not do that. I put the solid piece of pipe up to the fog machine. Good luck.
https://www.lowes.com/pd/ADS-4-in-x-10-ft-Corrugated-Solid-Pipe/3306082
https://www.lowes.com/pd/ADS-4-in-x-10-ft-Corrugated-Perforated-Pipe/3306090


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## Mattbhm (Oct 1, 2019)

stick said:


> I have tried different types of fog chillers and the best one for me and was the cheapest is a one 10' section of black ADS 4-in x 10-ft Corrugated Solid Pipe with one section (or more if have space *but* may need a fan to push it) of ADS 4-in x 10-ft Corrugated Perforated Pipe. If you want you can put ice in the solid section to help cool down the fog more but I do not do that. I put the solid piece of pipe up to the fog machine. Good luck.
> https://www.lowes.com/pd/ADS-4-in-x-10-ft-Corrugated-Solid-Pipe/3306082
> https://www.lowes.com/pd/ADS-4-in-x-10-ft-Corrugated-Perforated-Pipe/3306090


I'll definitely look into that! I already have a 10' piece of solid at home.

Thanks!


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## stick (Jan 21, 2009)

You are half way there then.


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## ajenka (Aug 13, 2015)

I have had good luck with this same basic design, I've been lucky enough to find old Igloo coolers on trash day and picked a few up over the years to use but I've also used a plastic tub and it worked fine. I put my main fogger inside a 6' x 3' x 3' tomb with slots cut on the bottom of the front for the fog to come out of, it covers my graveyard with a nice thick fog and makes a great centerpiece. If you do this make sure you have a way for fresh air to get in to your fog machine, like it says in the instructible you linked to, you need a good sized fog expansion chamber and plenty of fresh air in your chiller to get good fog.


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## Mattbhm (Oct 1, 2019)

ajenka said:


> I have had good luck with this same basic design, I've been lucky enough to find old Igloo coolers on trash day and picked a few up over the years to use but I've also used a plastic tub and it worked fine. I put my main fogger inside a 6' x 3' x 3' tomb with slots cut on the bottom of the front for the fog to come out of, it covers my graveyard with a nice thick fog and makes a great centerpiece. If you do this make sure you have a way for fresh air to get in to your fog machine, like it says in the instructible you linked to, you need a good sized fog expansion chamber and plenty of fresh air in your chiller to get good fog.


Yeah, I found a great deal on a very large plastic tub(40 gallon I believe) so I am sticking with my original design.

I have a fairly high CFM fan attached to a Y fitting at the intake where the fog comes into the chiller. I believe this would eliminate the need to have an open area between the fitting and fog machine? Or am I mistaken there?

Thanks!


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## corey872 (Jan 10, 2010)

My .02:

1) You really want the hot fog to burst into the cooler air gap as soon as exiting the machine. Search youtube for the 'boiling water into freezing sky" videos and note the fog that produces... same thing with your fog machine - those boiling drops of fog juice need to streak through the air to develop maximum 'fog'.

2) You really DON'T want a 'high CFM fan' for any part of this process. It will pump a bunch of air, very quickly, through your chiller. This means the air has very little time to cool and becomes turbulent - none of this is what you want to happen.

Ideally the fog would travel slowly through the chiller, have a long time to cool down and exit the chiller in a very smooth flow - allowing it to 'pour' out over the ground - and hopefully stay there.

I use a tiny (50mm x 50mm) computer fan to help direct fog through my chiller. Though sometimes I feel even that might be too much. It 'sort of' sticks to the ground but our weather (generally chilly air already and often a bit of wind) just don't allow for that 'ankle hugging' fog you might find indoors on a sound stage.


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## Mattbhm (Oct 1, 2019)

corey872 said:


> snip


Interesting.. I must say that by high CFM, I mean relative to a stock Dell(or other OEM) 50mm(probably what you have?). It is far from an actual high CFM cooling fan. When powered on, the exit of the cooler has a *very* slight breeze blowing out. The chiller box is also quite huge at 38"x22"x17" and will have a fairly solid layer of ice.

With that said, I will test with the current fan at full, 1/2 voltage and with no fan and compare the results.

I am not quite understanding your explanation on the air gap. Are you saying that it would not work to have an almost seal from the fog machine and Y pipe even with a fan blowing fresh cool air constantly into the stream of fog?

Thank you very much for the thorough explanations, I appreciate it.


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## Mattbhm (Oct 1, 2019)

It won't let me edit for some reason but I wanted to add that the reason I thought fan would be enough air is that the fog would be hitting an already moving stream of air. I felt like this would accelerate the mentioned process if anything. But I am wondering if the little(in perspective) fan wouldn't be producing near enough air in a 4" Y pipe to let the process happen.

I'm still figuring it out as you can see, haha.


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## corey872 (Jan 10, 2010)

Good points. I will add a bit to help with definition:

To the point of 'does there specifically need to be an 'air gap' (ie window/hole) in the pipe', then you are correct - no I don't believe you specifically need that. Though to the point of 'does there need to be an 'air space' (ie volume) for the fog to expand into' and I would generally say 'yes' to that. So how ever you manage to get air...an actual 'gap' or a fan forced 'injection', the fresh air should suffice.

I think a lot of people use the gap method as it serves two purposes - provides the 'fresh air' for max fog, and when properly spaced can create a 'venturi effect' which helps pump fog through the chiller. No need for the extra complexity of the fan.

On the fog/fan effect - I guess I was thinking just the opposite - fog bursting into 'stationary' air would have the maximum speed / max 'fogging' effect. Fog bursting into a fan stream of air would sort of be 'running with the wind' so to speak - it would have a 'tailwind' which would make the overall relative speed of fog through the air less. Though really, unless we're talking about a jetstream, the overall effect of fan vs no fan is probably pretty minimal.

Testing would certainly help guide you - just be careful... a lot of people test indoors/in a garage on a warm summer or early fall day and get "great results" with super ground hugging fog. Then go outside on a cooler, Halloween night with a bit of a breeze and the results are much less satisfactory.

Overall, it seems (at least to me) fog chilling is a fairly 'gentle' process. Seems to work best with lots of short bursts of fog, thoroughly chilled and allowed to spill gently out of the chiller with natural convection or a very slight boost. Any attempt to force the process creates less chilling, more turbulence and more fog rise.

Alternately - this year I'm going to try and work 'with' nature and add a laser for a 'liquid sky' effect above the grave yard - for any fog that does rise up and try to escape!


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## Tokwik (Oct 12, 2011)

corey872 said:


> Testing would certainly help guide you - just be careful... a lot of people test indoors/in a garage on a warm summer or early fall day and get "great results" with super ground hugging fog. Then go outside on a cooler, Halloween night with a bit of a breeze and the results are much less satisfactory.
> 
> Overall, it seems (at least to me) fog chilling is a fairly 'gentle' process. Seems to work best with lots of short bursts of fog, thoroughly chilled and allowed to spill gently out of the chiller with natural convection or a very slight boost. Any attempt to force the process creates less chilling, more turbulence and more fog rise.


These two things have worked best for me.

Outdoor setup testing. 
Nobody can beat the wind easily, but by testing outside you can figure out the weak points. My "perfect" spot in my head for the chiller is about 15 feet away from where the chiller "needs" to go. I ultize a couple things for wind breaks, and arrange other things accordingly so the fog can roll across the yard.

My experience with the fog is slow chilling is better. I don't use any fans to push fog. Same as Corey said above. Fill chamber with hot fog, let cool, next burst of hot fog "pushes" cold fog out of chiller. Slow and steady is the way to go. 
Wet ground also helps keep the fog low.

Good luck. Hope that helps some. Experimenting is fun.


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## OakLaneCemetery (Aug 21, 2016)

Yes you need an air gap of about an inch to two inches. If not you will have weak, thin fog no matter what juice you use or how good your chiller is. It is also better to run directly through ice vs through a pipe or tube coiled in the ice. The fog needs to pick up both cooling and moisture as it goes through the chiller. By isolating the fog from the ice you reduce the effect the ice has on the fog. I was astounded by the difference when I removed the coil of duct in my chiller and went to running directly through the ice. If you pipe your fog into the top of your chiller and pipe it out of the bottom you will have no need for any fans. Physics will do all the moving for you as the fog cools and settles as it will push out the fog in the bottom of the chiller.


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## OakLaneCemetery (Aug 21, 2016)




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## Tokwik (Oct 12, 2011)

Same as stated above. My experience is to always have the air gap. 
In my setup, the chiller is in the coffin behind the silhouette. Fog runs into the top, settles through the ice, and exits out the bottom.

Full disclosure, there is a fan. But it sits near the sidewalk blowing into the street for the sole purpose of dissipating the fog. Yard may be fogged, but the street is clear.

Previously posted pic from last year. 
Big machine, ice, and physics.


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## Sblanck (Sep 13, 2007)

If your budget improves:






I plan on doing this next season.


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## OakLaneCemetery (Aug 21, 2016)

Sblanck said:


> If your budget improves:
> 
> 
> 
> ...


This video is what made it click in my head why the fog does better passing directly through the ice vs passing through ice cold air. MOISTURE! The fog pics up moisture from the ice and the molecules become heavier, just as it does in this video by passing fog through humidified air. The moisture clings to the fog molecules and makes them larger and heavier! Makes perfect sense!


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## corey872 (Jan 10, 2010)

This is probably worthy of it's own thread to discuss.

I watched the video - was surprised by the results! Set up a test of my own and sure enough... ground hugging fog with the ultrasonic misters an no ice! ...at least in a 70F room. Will have to set up a test outside before the big night and see if the results can hold in 45ºF night air.

I will say - his system could be simplified by using a 'floating' mister. This is a holder with foam or an air bladder on top which floats on the water but keeps the misters submerged at an ideal depth. Using that, there would be no need for the pump and second container.

It is actually strange the fog sinks because the fact that water (as a vapor) is actually lighter than air and 'should' make it double hard for the fog to sink.

It is generally observed that when the ground is wet with water (ie high humidity / high water vapor / 'light air') the fog tends to stick / sink better. This is generally attributed to the cool fog being more dense and dropping in the 'light' / humid air.

Here are some highly technical videos, but the short of it is that a molecule of water - with two very light hydrogen atoms and one oxygen weighs less than 'air' which would be two nitrogen atoms / two oxygen atoms (in a roughly an 80/20 ratio)










I speculate that this method bypasses the 'light humidity' issue because the pond mister is actually kicking out microscopic droplets of water - and droplets of liquid water are generally heavier than air (ie - rain, mist, low-lying fog, etc, but not clouds!)

There may also be some effect of the fog machine fluid being a humectant - the glycerols / glycols of the fog fluid would want to absorb water vapor. So they could pull the light water vapor out of the air and lead to the whole mass of microscopic droplets sinking.

One thing I am curious about and he does mention - the ultrasonic foggers do heat up the water. I've clocked my misters at 10-12 watts each. Believe he was running 10? 4 misters seemed to keep up with my 400 watt fogger pretty well. But either way, you're dumping 10's if not 100's of watts of heat into the water. Again - more testing is in order, but does the effect still hold up as the water warms up??


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## corey872 (Jan 10, 2010)

Well, don't throw out the ice bucket just yet! I had a chance to set this up and try it out. For a very rough set-up I have a witches cauldron with 4 ultrasonic misters. I shot some Froggys Freezin Fog through a ~5 foot section of 2" PVC with a 90 degree elbow on the end to turn it down into the cauldron.

Initially, I set up in the basement and just like in the posted video - poof! a bunch of ground hugging fog - no ice needed.

The next test was outside in 55ºF calm air. Unfortunately, the results were a mixed bag. I would say 20-30% of the fog did come out and hug the ground, but the remainder came out of the cauldron and floated away waist to head high.

I will say one thing which might have hurt the effect - this time of year out water coming out of the tap is still warm due to the ground heat, but the air can get cool overnight, so my cauldron had ~75º water out of the tap. It might help to have cooler water - but there again - you need ice, and you'd be fighting the heat put in the water by the misters.

Either way, I would say try it before the big night!


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## fontgeek (Jul 24, 2006)

Something something that will help you keep your fog, if you can, put a low wall around the scene you want to fog. It can be tucked into a picket fence, hidden by bushes, stones, etc.
Wind/air movement makes the fog dissipate more quickly so you blocking the air movement at ground level will help you keep your fog where you want it.


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## Saturday8pm (Sep 5, 2012)

DANG these scenes are so impressive you guys should charge admission!


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