My niece and nephew want to add red and then blue food coloring to a container with dry ice to create a “fog” that will appear alternately red and blue for a 4th of Juky float.
I have googled this, but cannot find anything definitive which tells me this would work effectively enough to seen by parade watchers, so have any of you actually done this, and what were your methods and results?
Thanks
Q
This sounds like a job for pyrotechnics=>smoke.
Thanks!
I will go to one of those sites and see what I can find out!
Thanks
Quasi
Hello, Quasi.
ISTM that the ‘fog’ is coming from the ice, so food colouring in the water should make little or no difference. As I think about it, ISTR seeing glasses of green liquid with white ‘fog’ coming out from the dry ice. You might want to just pick up a piece of dry ice and try it out. (Of course, by ‘pick up’ I mean ‘buy’. Don’t literally pick it up without gloves!)
One thing I’ve noticed when playing with dry ice is that its output lessens fairly quickly, as water will freeze to it and exposing less of the ice. A friend built a fog machine out of a 35-gallon steel drum with a washing machine heating element in it to keep the water hot enough to keep the freezing to a minimum. (There was a fan and a hose, too.) Of course more exposed surface area means the dry ice is used up more quickly.
Pyrotechnics may be problematic on a float. First, there is danger of igniting the float. Second, pyro may not be permitted by the city and/or parade authorities. Your niece and nephew might get ahold of some smoke grenades, but they can get pretty hot. Or they may have to hire a pyrotechnician to do the job. Dry ice would be better/safer, but my guess is that the ‘fog’ will come out white regardless of the colour of the water. (I stand to be corrected.)
The food coloring is not going to change the color of the vapor.
I asked my son who use to do lighting for shows. His suggestion is colored lights shining through the fog.
(Did you think I forgot???)
Dear Friend,
You ROCK!
We’re shelving that idea till next year.
Warmly,
Quasi
Here’sa company explaining why you can’t make dry ice fog machine fog colorful.
Here’s a place that sells safe professional products to make colored smoke instead, but it looks to work out to over two bucks a minute, and probably a lot greater output than needed/wanted for this project. However, the item description there also suggests that you could recover the charge powder and refactor the output yourself to be more gradual/subtle/cost effective with a couple of these doodads… Doesn’t seem like a bad option, with some shopping around!
And then there’s the lower-quality colored smoke bombs from manufacturers like Black Cat, et al… Or make your own! 
With any of these the “acridity” of the smoke might be of concern, depending on how thick they plan to lay it on.
Well, I was mostly guessing; but the other posts indicate the fog will indeed be white.
Watch out for the Time Holes, eh? 
In the interests of Fighting Ignorance, the above link is for a fogging machine. These work differently to a dry ice machine. The fogger drops a glycerol solution onto a hot plate vaporising it to make the “smoke”. A dry ice fogger sublimates the CO2.
t.
Serious side question: What if you put drops of food coloring directly ON the chunk of dry ice, completely covering it?
I don’t think you’ll see it. First you’ve got the quantity issue - intuitively I’d expect only a very small amount gets vapourised so it would be very subtle.
And the second issue - would the colour vaporise too? I’d think not as you need heat to vaporise the liquid and the dry ice is vaporising only because it’s boiling point is very very low.
Thinking back to TV where they have a pot of flourescene glowing away with dry ice bubbling over the top, I never saw any colour transfer to the fog.
Would be cool if somebody could try and report back though!
Individual fog droplets are on the order of 5 to 35 micrometers in diameter, so you need a very dark dye to get a visible color. Even black spray paint fails to impress with it’s color before the mist hits a solid surface.
Okay, what if you dropped a chunk of dry ice into, say, a gallon of concentrated red food coloring?
Would be very expensive! Unless you’re asking theoretically?
Q
No dropping dry ice into pure food coloring is not going to produce colored fog, but even if it did, do you think you would want food coloring fogging all over the street? I’m guessing some parents might be a bit upset at the damage to their childs special July 4th outfit.
I don’t know if Zubbles are available in stores yet, but pink and blue bubbles would be pretty cool for the fourth of July. No stains! They are a bit pricey though, and I don’t think you will get then in time if you order them online.
Learn something new everyday! I didn’t know there were multiple kinds, thanks for the info.
IME dry-ice foggers make fog that hugs the ground, as it is cold and heavy. The glycerol foggers make an aerial fog. In addition to ‘fog’, this kind is also useful for adding ‘density’ to a filmed scene. The image doesn’t look foggy (if you’ve dispersed it correctly), but it adds a nice ‘density’.
Basically what you see as “dry ice fog” is aerial moisture condensating in the cold CO2 relased by the sublimating dry ice. Non-volatile dyes do not evaporate, therefore the fog does not get colored ( I have tried it).