You'd be surprised what you can do to keep food fresh (or frozen) with dry ice.
As a caterer who specializes in off-premise catering, I have to know all about dry ice and how to use it. Dry ice and cube ice are the solutions to my refrigeration and freezer problems. So I use them a lot.
Here's something else... We also use dry ice for an "everything but the kitchen sink" cocktail that we serve at parties. People freak out when they see it!
It's an impressive cocktail. It has a ton of ingredients in it, so it's large (recommended for up to four people, and no less than two people). Consequently, the hosts who order it for their parties find that it becomes the talk of their party. It always gets rave reviews and leaves people talking about it for weeks!
So after years of producing off-premise parties, we've got dry ice down pat. I've had clients ask me how to make dry ice, and I have to admit - I have no idea, because we always buy it. We buy crushed, cubed, shaved and dry ice from a large ice supplier that supplies ice to grocery stores and gas stations, and restaurants and country clubs.
Cater-Hater Tip: You can save a substantial amount of money on ice, whether you need a large quantity of ice like we often do, or not. We sometimes cater parties for people who invite 1000 guests. When we do, our ice supplier not only sells us the ice - they bring it to us, along with one of their commercial ice chests (like the ones you find, outside, at gas stations) for storage at our party location. Whatever the size of your party - save money! Buy ice from the company that supplies it to businesses that sell it to you. What you'll find is, not only will it cost you less money - the size of the bags are will be larger, too (25 lb. bags from the supplier instead of 5 lb. or 10 lb. bags you buy from everyone else).
Dry ice is serious stuff.
Dry ice experiments aren't something I'd recommend because dry ice is tricky. If you don't know what you're doing, dry ice can be downright dangerous.
Dry ice "science".
Sometimes dry ice is made on the spot from liquid C02. It's great when it's done that way; resulting in dry ice snow, it is packed in the top of shipping containers, for example. This will offer you extended cooling without using electrical refrigeration equipment and connections.
You know about carbon dioxide. It's the gas that we exhale during breathing and it's the gas that plants use in photosynthesis. It's also the same gas commonly added to water to make soda water or sparkling water.
I use dry ice for freezing and keeping things frozen because of it's very cold temperature: -109.3F to -78.5C. It's simple to freeze things with it, and it's easy to handle as long as you use insulated gloves.
How long does dry ice last?
As a general rule, dry ice will last or sublimate at a rate of five to ten pounds every 24 hours in a typical ice chest. We use heavy duty or commercial grade ice chests which makes the dry ice last even longer. Melting or sublimation continues from the time the dry ice is purchased, so we try to buy our dry ice as close to the time we need it as possible. Of course, we bring ice chests to hold the ice, which also slows the sublimation process. Always wrap dry ice in newspaper or old towels before placing it into any ice chest. If you don't, there's a large chance that the interior wall of the chest will crack.
Never store dry ice in the freezer!
It's best not to store dry ice in your freezer because your freezer's thermostat will shut off the freezer due to the extreme cold of the dry ice. If the freezer is broken or if your power goes out, dry ice will save all of your frozen goods.
You can use dry ice to ship perishables and even non-frozen goods. When you use dry ice for transporting food products, for example - it will give you more than twice the cooling energy per pound of weight and three times the cooling energy per volume that regular frozen ice ( frozen H2O).
Mix regular ice with dry ice to save on weight and to extend the cooling energy of the regular ice made from water.
The basic rule of thumb is: Be careful when you use dry ice, and be prepared to spend a little extra when you need to use it. Like everything else - it used to be pretty cheap, but not anymore.
