Dry ice is the secret ingredient for all that spooky fog you see at Halloween, whether it's billowing from a witch's cauldron of punch or creating a generally creepy atmosphere wending its way through your Halloween display.
If you're wondering what dry ice is, it's definitely not witchcraft. Dry ice is just plain old carbon dioxide, frozen solid at a very low temperature (-109 degrees Fahrenheit, to be exact). When it comes in contact with a liquid—or at room temperature—it sublimates, or melts right away into gas.
How to Use Dry Ice Safely
Dry ice isn't toxic, but it can be dangerous, causing terrible burns just a moment after coming in contact with skin. Be sure to take safety precautions whenever handling dry ice: Always use tools like tongs to move it around, along with heavy duty gloves, safety goggles, closed-toed shoes, and long sleeves and long pants.
How to Make Your Own Dry Ice
While it's much easier to buy dry ice at a grocery store or ice supplier, you can also make small amounts yourself. What you need is a carbon dioxide fire extinguisher (these usually aren't the standard fire extinguishers you have in your home—look for the kind that has a black cone, like this) and a tightly woven pillowcase.
To make the dry ice, wrap the pillow tightly around the fire extinguisher nozzle, then press the lever. (Important: Make sure you are taking the proper safety precautions mentioned above!) Tiny pieces of dry ice will develop inside the pillowcase. You can then pour it into a heavy duty plastic container for use.
How to Store Dry Ice
You can store dry ice at home for a short period of time, but you'll probably want to pick up dry ice just a few hours before your party.
Keep it out of reach of small children and animals, and make sure you store dry ice in an appropriate container. A heavy-duty plastic or styrofoam container is best, but avoid tightly covering it. If the lid is air tight, the carbon dioxide could build up within the container as it sublimates, and eventually explode the container. Wrapping the dry ice in newspaper or towels can help minimize the exposure to air, and slow the melting.
To dispose of dry ice when you're done, just leave it in a safe, well-ventilated spot where it's exposed to air—it will gradually sublimate and disappear.
How to Use Dry Ice For Halloween
Dry ice can be fun to give your Halloween party an extra spooky vibe. To safely add a smoky effect to your punch, use two bowls: Put the Halloween punch in the smaller bowl, then nestle that into a larger punch bowl or cauldron. Before serving, place small pieces of dry ice in the space between the larger and the smaller bowl, and pour in some water to activate the dry ice.
Dry ice is not edible, and can cause serious internal injuries if it's ingested, so avoid putting dry ice right into your Halloween punch, unless you can be certain it's completely melted before someone takes a sip.
To get spooky dry ice fog for your Halloween display, set a larger piece of dry ice into a small bucket or dish of water. You can use a small fan on a low speed to help spread the fog where you want it to go. It's also a cool effect to place a small piece in a dish within a jack o'lantern, and let smoke billow out from it.
Using warm water to activate the dry ice will create thicker fog, but will make the dry ice disappear faster—use colder water if you want a slower, gentler effect.