I have never made liquid nitrogen.  I do make dry ice ice cream about 4 times a year.  Kids love the carbonation.  My daughter says it is like an automatic root beer float (even though we don’t make it root beer flavored).  Here is the procedure I keep for our Demo Squad (of course, with me, they are required to fill out a risk assessment form before the demo):

 

Materials

• Dry Ice
• 2 cups- heavy whipping cream
• 2 cups- half- and- half
• =BE cup- sugar
• 2 tsp- vanilla extract
• Sprinkles (if desired)
• Chocolate sauce (if desired)
• Bowls for making dry ice ice cream
• Mixing spoons
• Goggles
• Gloves

What To Do

 

1. Demo day set up

A.    Crush the dry ice into little pieces.

1.      Place in paper bag and smash with a mallet

B.     Mix all other ingredients in a large bowl

2. For the demo/activity

A.    Shake the dry ice into the ice cream, a little at a time

1.      Mixing in between additions

B.     When adding more dry ice, it will start to harden, and get more difficult to mix.

C.    Continue adding dry ice until the ice cream reaches the desired consistency.

D.    Remove stray chunks of dry ice with a small fork, or spoon

1.      Once all dry ice been removed, enjoy

3.      Post Demo Clean Up

A.    Clean the bowls and spoons

B.     Put dry ice away in a -90^oC freezer, or let it sublimate in a fume hood

 

What’s Happening

Dry Ice is frozen carbon dioxide, which is part of the earth’s atmosphere. The temperature of dry ice is -78.5^oC, so it can help things freeze and be kept frozen. When breaking up the chunks of dry ice at normal temperature of the atmosphere, the ice will turn from a solid to a gas through sublimation. When the dry ice is added to the ice cream mixture, the mixture will start to thicken up, a little at a time, and there will be some CO2 bubbles forming. When you get to the consistency that you want, stop adding the dry ice, or it will become harder to stir, and hard to scoop. When done at the consistency you want, scoop out the dry ice pieces that didn’t break up, so you don’t eat any (this could lead to asphyxiation or cause other health affects). Then make a bowl or a cup with whatever toppings you want.  The tangy flavor is from the CO2 that bubbled through the liquid ice cream mixture.

 

Hazards

Dry Ice is a cryogenic material which has a boiling temperature of less than -73^oC. It can cause tissue damage and asphyxiation due to oxygen displacement. It also poses as a fire hazard if the oxygen is condensed out of the atmosphere. Dry ice ice cream is simple to freeze so insulated gloves are appropriate.  Try to stand back while breaking the chunks or handling or have a fan available to keep air circulating so you don’t breathe in large amounts of the CO₂.

 

 

 

I wonder - could you do similar with crushed dry ice?  Sounds like a weekend project to me …..

 

Thanks for the recipe, David.  In the absence of LN2, that’d freeze up nicely in an ice cream freezer, too.

 

Debbie M. Decker, CCHO, ACS Fellow

Immediate Past Chair, Division of Chemical Health and Safety

University of California, Davis

(530)754-7964

(530)304-6728

dmdecker**At_Symbol_Here**ucdavis.edu

 

Birkett's hypothesis: "Any chemical reaction

that proceeds smoothly under normal conditions,

can proceed violently in the presence of an idiot."

 

 

 

 

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