Liquid Nitrogen Dry Fogger

I'm looking into using LN2 for a specific "vanish" effect which I don't believe can be achieved with more conventional means (i.e. dry ice, co2, etc). Does anybody here have any experience working with it? Having spent the last few hours on Google, i've been unable to find any dry fogger machines that work with the stuff. Considering the desired blast of fog only occurs once during the performance and should only last a few seconds, how feasible would it be to make my own dry fogger? I was thinking something along the lines of an old cooler box with a hole cut out for ducting. Hot water sits at the bottom. When it's time for the fog blast, the required amount of LN2 is places in a bucket above the hot water and the box's lid is shut. Via some mechanism, the bucket of LN2 is tipped into the water and "hey presto!". A crude method perhaps, but would work similarly to a traditional dry ice "pea soupper".

With regards to safety, I've performed the necessary Oxygen depletion calculations for our stage size (not even taking into account the size of the auditorium) and we could safely store 25ltr of LN2 in a dewar tank offstage without the O2 levels falling below 20% in a worst case scenario (i.e. the whole lots spills out of the tank). Procedures will also be in place for the correct and safe handling of the liquid.

When we did Wizard of Oz, I just went to rent some pretty hefty CO2 extinguishers. I was willing to pay but our local extinguisher guy thought it was cool to be involved and gave me 3 to rotate, and I carried them back to him for refill. He did it all for just an acknowlegement in the program, without me even asking for the donation.

Thanks for the suggestion but pure Co2 really isn't going to cut it.

ececec said:

Thanks for the suggestion but pure Co2 really isn't going to cut it.

Click to expand...

Can you be more specific as to why. Not trying to be argumentative just trying to wrap my head around what you are trying to do.

I do not have a lot of experience with LN2 but to my understanding once you get to that level it is strictly cryogenic jets. Essentially just a valve and a diffuser. There is no machine really to speak of.

ececec said:

for a specific "vanish" effect

Click to expand...

What is the actual effect you're looking for? Covering a scene change? A performing disappearing? If it's a performer disappearing, how do they disappear?

ececec said:

With regards to safety, I've performed the necessary Oxygen depletion calculations for our stage size

Click to expand...

Need to factor in that you also shouldn't immerse/submerge a performer in it, which may or may not disrupt your intended effect.

BTW -- actual LN2 foggers use a special fluid to throw more visible particulate into the air, and I wouldn't describe LN2 as a dry fogger -- they can still create condensation that can make a surface slippery.

Here's a video of what you can expect if you do it like you describe. It's kind of an uncontrolled release and has to be pretty darn close to what you're trying to mask.

The fog from a CO2 jet dissipates too quickly and doesn't generally fall nicely to the ground when switched off.

MNicolai said:

What is the actual effect you're looking for? Covering a scene change? A performing disappearing? If it's a performer disappearing, how do they disappear?


Need to factor in that you also shouldn't immerse/submerge a performer in it, which may or may not disrupt your intended effect.

BTW -- actual LN2 foggers use a special fluid to throw more visible particulate into the air, and I wouldn't describe LN2 as a dry fogger -- they can still create condensation that can make a surface slippery.

Here's a video of what you can expect if you do it like you describe. It's kind of an uncontrolled release and has to be pretty darn close to what you're trying to mask.

Click to expand...

It's for an appearing performer, coming up through a trap in the stage. The fog outlet would need to be positioned in front of this. I imagine that the brief time spent coming up through it shouldn't pose too much of a suffocation risk.

BTW -- actual LN2 foggers use a special fluid to throw more visible particulate into the air,

Click to expand...

Click to expand...

Do you have any sources for this? Sounds like you know your stuff on this. Is there any other info you can share?

Here's a video of what you can expect if you do it like you describe

Click to expand...

Perhaps doing it the other way round and slowly releasing hot water into the LN2 for the desired density would work.

In terms of volume, approx how much LN2 would you need for 1 min of operation in an average setup? Or, what would be the equivalent amount to 5lb of dry ice?

Thanks!

Dover said:

I do not have a lot of experience with LN2 but to my understanding once you get to that level it is strictly cryogenic jets. Essentially just a valve and a diffuser. There is no machine really to speak of.

Click to expand...

Thanks. Any more info on this? Can you clarify what you mean by diffuser?

ececec said:

It's for an appearing performer, coming up through a trap in the stage. The fog outlet would need to be positioned in front of this. I imagine that the brief time spent coming up through it shouldn't pose too much of a suffocation risk.

Click to expand...

The risk isn't suffocation, per se, it's that it displaces oxygen causing asphyxiation. This can happen very quickly, in under less than a minute. Same thing for CO2 effects. In the case of your effect, I would be concerned by how long the performer is in proximity to the plume. Really depends on the volumes of areas though and density of the effect though.

Most of my experience is with liquid CO2 fog, not liquid nitrogen, so I can't give you much more info than this. There used to be a company out of Chicago that created custom LN2 systems for rentals and had some info on their site, but generally speaking, it was a niche market and more expensive to deploy than liquid CO2 fog. Fairly certain that company isn't even in business anymore and the website is gone.

ececec said:

Thanks. Any more info on this?

Click to expand...

Here's a simple version. Granted, this guy lives down the street from me here in Sarasota and our Florida humidity may make the effect more extreme than you might expect from an indoor, conditioned space.

To view this content we will need your consent to set third party cookies.
For more detailed information, see our cookies page.

Accept third party cookies

I would say the performer's head would only be at stage height for a few seconds.

I think dry ice would produce an acceptable effect, however in the small quantities we'd need it's just not financially feasible to arrange daily delivery when you take into account it only lasts for 24-48 hours (probably less when using only 5kg). Is there a way to produce a dry fogger effect with liquid Co2 from a canister? By which I mean, no fog fluid - just hot water and liquid Co2.

we have an effect thats similar in our show, where an actor disappears behind a wall of intense fog to reveal an object where he was standing only a couple seconds before. its a fogger using fast dissipation fluid run through a cooler system that also uses the CO2 to propel the fog up. Creates a nice wall of fog that drops as soon as the effect is turned off.

DuckJordan said:

we have an effect thats similar in our show, where an actor disappears behind a wall of intense fog to reveal an object where he was standing only a couple seconds before. its a fogger using fast dissipation fluid run through a cooler system that also uses the CO2 to propel the fog up. Creates a nice wall of fog that drops as soon as the effect is turned off.

Click to expand...

Thanks! I wondered this might work nicely. My main concern with using fog fluid is that it doesn't dissipate fast enough and give that nice fog-falling-to-the-ground effect. Is there any chance you'd be happy to share a video of the effect so I can get an idea of what's possible?

ececec said:

Thanks! I wondered this might work nicely. My main concern with using fog fluid is that it doesn't dissipate fast enough and give that nice fog-falling-to-the-ground effect. Is there any chance you'd be happy to share a video of the effect so I can get an idea of what's possible?

Click to expand...

Unfortunately I cannot due to the mouse's lawyers. I can tell you what equipment is used and which fluid however.

Yes please, and any other information you think might be useful. Thanks!

I just reviewed my horizontal blast For Santa’s sleigh in ELF. from my geyser unit using froggys fast dissipating fog. Had about a 7 second hang time before being mostly gone. 2 geysers DMX control gives you everything you want except the fall back to ground. You get much more safety. Low materials cost . Repeatability tune ability. And booth control.

jtweigandt said:

I just reviewed my horizontal blast For Santa’s sleigh in ELF. from my geyser unit using froggys fast dissipating fog. Had about a 7 second hang time before being mostly gone. 2 geysers DMX control gives you everything you want except the fall back to ground. You get much more safety. Low materials cost . Repeatability tune ability. And booth control.

Click to expand...

Thank you. I would say the falling back to the ground and fast dissipation is quite essential to the effect we're going for so will be pursuing the cryogenics route.

For folks working with liquid N2 in labs, most safety training focuses on keeping N2 droplets out of the eyes and away from the face, hands/arms and feet. It seems some level of PPE and training would be for crew and cast.

In the Yee Olde Dayz® we'd have done this with lights and a scrim. Since this is to camouflage the actor entrance via trap door, I suggest that the LX do the heavy lifting of focusing attention and reconsider the use of cryo at the operating distances from the talent as the substitute for the scrim. There are other products with use/safety data and directions that might prove less risky and/or have demonstrated and repeatable exposure data.

If this is for a school, I'd expect at least one student family to have LOTS of questions regarding the use of nitrogen. Current events, etc.