I’ve got a halloween party on Saturday and my girlfriend wants to make a Witches Brew type thing. First tell me where to get it, then tell me about the logistics of handling and using dry ice. Is it expensive? How about transporting it? How long does something like that last? How much do I need, etc?
Most ice suppliers have it; look in your Yellow Pages. You can keep it in an ordinary foam cooler for quite a while, and the only special handling is to wear heavy gloves when picking it up. Since it evaporates into carbon dioxide gas, you want to have ventilation where you’ll be transporting and storing it. It’s not very expensive at all.
The local Tom Thumb grocery stores have an insulated cooler full of it in the front of the store. It’s $1.00 per pound. You’ll probably need 5 or 6 pounds.
If you’ve got a Meijer nearby, I can almost guarantee they’ll have it up at the front of the store.
As a matter of fact we do have one right down the street, but I can’t for the life of me remember ever seeing dry ice for sale there.
You’ll have to look around a bit. It might be in the yellow pages. Grocery stores will sometimes carry dry ice. Try calling around. Also, sometimes ice companies (the guys who deliver those bags to grocery stores, gas stations, and so on) also sell dry ice. Make sure you tell them you want food grade.
Dry ice should be fairly cheap. You can make it yourself if you have the right equipment (which you won’t.) I’ve done it a lot for lab work. Dry ice is made by forcing CO2 gas under high pressure through a membrane. The laws of thermodynamics do the rest.
Anyway, dry ice can be safely transported in a cooler. Keep the block together for as long as possible, as that will cut down on the amount of sublimation. The stuff is cold and will freeze to your skin quickly if you have moisture on your skin. I suggest grabbing a pair of latex gloves if you’re going to handle it by hand or otherwise use a pair of tongs. Q.E.D. mentions a heavy pair of gloves, but in my experience you can work quickly barehanded or with latex or nitrile gloves. Large amounts of contact for long periods do require heavy gloves. Your winter gloves should be plenty. Use some in your drink and keep the rest in the cooler (and even put the cooler in a freezer if you’ve got room). Pack any dead air with plastic or paper bags, as that will cut down on the rate of sublimation.
Possible sources include ice companies, ice cream shops, butcher shops, and specialty grocery stores. You’ll probably want at least 5 pounds, maybe 10 to be on the safe side. I think it was less than $1 per pound when I last got some.
A 10 lb. hunk is something like 10-12" square by 3 or 4" thick. It typically lasts about 24 hours once out of the special freezer where it’s stored. Of course it’s dwindling throughout that time. For the “witch’s brew” it’s placed in a kettle of water, and I don’t what effect, if any, the water has on its longevity.
Take a big enough cooler for transporting it. It’s usually wrapped in newspaper - this prevents the “skin instantly stuck to it” problem. You can pick it up thus wrapped with bare hands, but only very briefly. Gloves are a very wise precaution, and necessary if you handle it unwrapped (if say, you don’t want the paper in the water).
Don’t try to seal it in something airtight. It develops a compelling amount of vapor pressure as it sublimates.
It’s by the exit. If we’re talking about the one off Golf and Algonquin, that is.
A couple of notes, based on personal experience with the stuff:
Heavy gloves are nice, but generally, you can handle a big block of dry ice just by handling it through the thick brown paper it’s usually wrapped in. Paper is a poor conductor of heat (or lack thereof), and as long as your contact with it isn’t excessive and sustained, you’ll be golden.
Do NOT try to extend the life of your dry ice by putting it in your home freezer! Two reasons: first, as the dry ice sublimates into a gas, it’ll be expanding and possibly building up pressure (for this reason, also don’t close the latch on whatever cooler you put the stuff in). You don’t want that. Also, the freezer will actually shorten the life of your block of dry ice, because the air in the cool freezer will cause water condensation on your dry ice, which will hasten its sublimation. Just leave it stashed in the cooler.
On using it for fog effects: the effect is stronger if the water you put the dry ice in is warm or even hot. If you’re using dry ice in hot water, through, avoid glass containers, or anything likely to shatter when hit with a sharp pressure differential. Also, you’ll get more fog more quickly if the ice is in smaller chunks or, better yet, crushed into powder. On the downside, this will use up your ice faster.
Dry ice makes very eerie sounds when it comes into contact with metal. Remember that creepy sound at the beginning of The Texas Chainsaw Massacre, after the flashbulbs went off? That was metal on dry ice. Press the flat side of a butter knife against it, you’ll see what I mean. But if you do, don’t subsequently put your tongue on the now-very-cold knife. Ouchies.
Well damn. As a matter of fact, yes, that’s exactly the one I was talking about. I’m used to the Dope being helpful, but *directions * are a new one on me. 