Which works better?

[renegade]

I am going to build a dry ice fogger and would like your input. Which type of machine will produce the most consistant, heaviest, longest lasting fog. A basket system to dunk the dry ice in hot water, or a pump system that pumps the hot water onto the dry ice?

 

[seanandkate]

The faster the ice melts, the more fog you get (all things being equal). So the longer you can keep the water that's melting the ice hot, the more fog you get more quickly. That being said, there are tons of variables.
Consistant: You want the ice to melt at the same rate throughout. A basket will melt an ever-decreasing-in-size chunk of ice in getting-ever-cooler water. A pump system will help with the latter, and the larger the piece to begin with will help moderate the former.
Heaviest: Much of this will depend on the ambient air temperature, the air flow of the space and the amount of fog being generated. Hard to know how it will react until you actually test it in the space.
Longest lasting: Affected by the same variables as above.
Have you thought about trying a Rosco Coldflow or similar that uses a tank of CO2 instead of dry ice? That would certainly solve much of your "consistency" concern.

 

[Footer]

In general, pump systems will give you a better effect. The initial burst will not be as much as a peasouper but it will last longer. Pump systems are harder to make and are more expensive. It really just boils down do how long you expect the effect to last. A peasouper won't make it through the Dance of the SnowFlakes.

 

[shiben]

In general, pump systems will give you a better effect. The initial burst will not be as much as a peasouper but it will last longer. Pump systems are harder to make and are more expensive. It really just boils down do how long you expect the effect to last. A peasouper won't make it through the Dance of the SnowFlakes.

So im not familiar with this type of thing, but is a peasouper one that just dumps a measure of water into contact with the ice? If so, couldnt you just pipe in more water (like a small fire hose) to make more at first and longer? Again, just kind of tossing this about, more interested in why thats a bad idea vs something to try...

 

[renegade]

Thanks to all. The plan is to use the machine to create a fog curtain and low lying fog on the set for an Easter production. The fog needs to last about 8 minutes. Most of the equipment is already acquired. The only problem with a ready-made machine is budget constraints (budget? What budget!) and I've never used Liquid co2 so I wouldnt be as comfortable with it. (safety first) that being said, how long would 10 lbs of dry ice last?

 

[farmerjo1111]

In my experience 10lbs of dry ice will last about 5 seconds. To do continuous 8 min of fog your going to need a couple of hundred pounds of dry ice.

 

[Scarrgo]

We use a home made super fogger(thats what he calls it) and it works really well...
It has to heater elements that you can turn on and off with a switch and there is a temp gauge(its set at 150) and pumps the water on to the Ice (Pellets work best IMO)

As others have said, to do a long effect like that its going to use a lot of ice

Sean...

P.S. dont forget about the condensation on the floor, a long effect like that might make the floor pretty wet

 

[SHARYNF]

Personally I don't think dry ice will work for that long an effect, and as mentioned the cooling effect is going to cause a lot of condensation. I think you probably need to look at a chiller for a fog machine, and long hang time fog. 8 minutes is a LONG time
Sharyn

 

[FatherMurphy]

I've made fog chillers from picnic coolers, cutting 3" to 4" pipe flanges into either end (sized to match the dryer hose we were using to pipe the fog onto stage), with 5-10 lbs dry ice cubed and laid out on a screen mounted inside the cooler (one pipe flange high, one low, fog passing through the screen to travel through the cooler). Might have had a 4" muffin fan to force the draft too, can't remember for sure.

Chilled chemical fog usually has a good hang time, and will stay close to the floor, although it can start to rise as it warms up, it depends on the light cue and building air currents.

 

[itlightsup]

We built our own dry ice fogger for a bride who wanted to have first dance in the clouds. we had a large insulated cooler, a heating element keeping the water at just around 175, a pump to feed the water up to a tray, and a fan that then blew the fog out of a movable vent.

The theory was there I swear to you, but after about 150lbs of pre-crushed ice, so that it would all dissipate the same, we still only got about 3 minutes out of the whole thing.

If I had to do it again, I would buy a low-lying heavy grade fogger and just be done with it. Opportunity costs and all...

Cheers.

 

[MPowers]

Longest lasting would be either Liquid Air (80% LN2 and 20% LO2) or straight LN2. the machines are expensive running $4K to $12K and more (LOTS of different versions available, thus the wide range of prices). Most Fog suddenly, a Pea Souper or similar device that pumps the heated water over pellets or crushed Dry Ice. Everything else is in between. The most condensation, usually developed on the floor, is CO2 units, least condensation is Liquid Air. Liquid air is the only fog that actors can work in completely immersed, for indefinite periods of time, as it is exactly what it's name implies, AIR. It is also the most expensive and to my knowledge, all liquid air fog machines are one-off, manufactured only when ordered and a down payment has been made.

 

[MPowers]

....We built our own ...... the water at just around 175, a pump .......a fan that then blew the fog ...... about 150lbs of pre-crushed ice, .....we still only got about 3 minutes out of the whole thing.Cheers.....

Really, really strange. The description sounds like a classic, standard fog machine. The only things I can figure is the volume of water and the actual water temp. If the total volume of water was less than roughly 30 gallons, then it probably was chilled too rapidly to continue producing fog for very long. If the water temp was lower than you thought, the result would be the same. The only other thing I can think of is the diameter/length/straight run of the delivery hose. If it is less than 5" or 6" and has a run of over 20' or sharp bends of 90 degrees, then there will be problems. If you ever have time to scope this out, I'd be interested in finding out what the problems was, as it really should have worked, and worked quite well.

 

[ptero]

I'm guessing you won't get into LN2 due to money constraints. BUT. In addition to moisture, we had regular ice buildup on the floor where it hit coming out of the hose. In our case, a stagehand in black with a black towel would sneak out and wipe the area clean (in the alley, any flashbacks Michael?) w/o being seen while the scene played. It softened and melted quickly enough for this. I believe we had just the LN2, w/o LO2 mixed in.

 

[MPowers]

It was straight LN2. Liquid air was far beyond our budget at the time. Liquid Air would have solved or made moot the problem with the parents of the performer that "had a problem with the fog".

BTW, That old machine still in use???

 

[ptero]

Hah, yep, poor kid just collapsed when it crested his head. The taller adult Scrooge was out there wondering "Where'd he go?" Kid got right up as soon as the cloud cleared and the scene continued.

We went to a Cryo fogger this season, Look Solutions I believe. Really nice. The LN2 is no longer in use, but I think we still own it. The former P.M. borrows/(rents?) it now and then for his school system. Heater controls started aging and going cryo will save $$ over time. Just like the LN2 was cheaper than Dry Ice over a number of years.

We still do the 'dry ice in a hot coffee pot' for Old Joe. We tried making it with a CO2 fed pipe/tool from somewhere that just didn't pack it hard enough. It made cylinders of a kind of soft dry ice maybe 4" x 12" or 18". It was cheap to make the dry ice, but unfortunately it wouldn't last long enough.