How to use dry ice for Halloween

By Sara Elliot

Making spooky fog is an effective visual effect for a Halloween celebration. A roiling caldron, bubbling punch bowl or fog shrouded buffet table can be pretty dramatic and easy to achieve. All you need is a block of dry ice and a few tips and warnings about how to use it.

Dry ice is pretty cool — literally. It’s made of compressed carbon dioxide (CO2) with a temperature of -109 degrees F. When CO2begins to melt, it converts to carbon dioxide gas. Adding hot water to chunks of dry ice (or adding another liquid like punch), will speed up the conversion and create a distinctive, creepy fog.

When carbon dioxide goes from a gaseous to a liquid state under pressure and is then subjected to a swift change in pressure, it flash freezes. When you buy dry ice (frozen CO2) and add water, the carbon dioxide converts back to a gas again. The warmer the water, the faster the conversion (sublimation) process will be. You’ll produce more fog, but for a shorter period of time.

Dry ice doesn’t convert to a gas in even increments, especially if you’re using it in a hot water solution. To use dry ice efficiently, it pays to plan the effect you want and combine hot, warm or cool water and dry ice at the last minute — or arrange multiple, sequential dry ice displays every half-hour or so.

Where To Purchase Dry Ice

Around Halloween, you can often find dry ice at your local market or variety store. Year round, it’s sold by ice wholesalers and companies that sell shipping supplies (because dry ice is often used to keep perishables cold during transport). It’s also sometimes marketed through food supply wholesalers. Try checking your local yellow page listings, or perform a general web search for your area.

During October, dry ice is in big demand, so find a source and reserve your order in advance, especially if you plan on using it during the last week of the month. For the best results, always make your purchase just before you plan on using it.

How Much Dry Ice Do You Need For Decorations?

To give you an idea of the quantity you’ll need, here are some popular uses for dry ice with volumes and approximate duration times for fog production:

Used inside a pumpkin — 3 pounds of dry ice will produce fog for about a half-hour in warm water.

Added to a witch’s cauldron — 10 pounds of dry ice will last for about 40 minutes in warm water.

Added to a large punch bowl — 5 pounds of dry ice will produce fog for about 40 minutes in cool water.

Used in a small room or entry — 30 pounds of dry ice (split into two containers) will last 45 minutes to an hour in warm water.

Used on a porch or deck — 50 pounds of dry ice (split into two containers) will last up to an hour in warm water.

Safe Methods for Using Dry Ice

– Because dry ice is very cold, it can be dangerous. This is one Halloween effect that should be supervised carefully by grown-ups:

– Always handle dry ice with gloves or a towel. It can cause nasty burns if it comes in contact with bare skin.

– Melting dry ice displaces air, so make sure to use it where there’s plenty of ventilation.

– Never eat dry ice. It can cause internal injuries. (You can drink punch or other beverages after dry ice has melted away, though.)

– Preserve dry ice by keeping it in an insulated container, but make sure that the container IS NOT airtight. Dry ice produces CO2 gas. If there’s no place for the expanding gas to go, it can cause the container to burst.

Fun Halloween Ideas Using Dry Ice

Here are some ideas for using dry ice you may not have considered:

Creepy bubbles — In a tall glass container, add two cups of water, green food coloring and two teaspoons of dish washing liquid. Now add a small piece of dry ice. Bubbles will “grow” out of the glass and dribble down the sides like a science experiment gone horribly wrong.

Scary Jack-O-Lantern — Carve your favorite scary face into a pumpkin, and place a cup of hot water inside. Add dry ice to the cup using tongs (not your fingers), and put the top on the pumpkin. Fog will drift out of the face you’ve carved for a dramatic effect.

Laser fog — Use a laser pointer or other laser device to create a dramatic light show through a cloud of dry ice fog.

Menacing Punchbowl — Wrap a block of dry ice in a towel, and hit it with a hammer until you break off small shards. Add the shards to punch or other beverages using tongs or gloves. (Another nice punchbowl effect is to fill rubber gloves with water and freeze them for custom hand shaped ice cubes).

Foggy front porch — To create spooky fog on your front porch, use a shatterproof container that holds three to five gallons of water. For an even distribution of vapor, use two containers — one on either side of your front steps or doorway. About 75 pounds of dry ice added to warm water and refreshed three times or so will keep your porch foggy for a couple of hours

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