Making Ice Cream with Snow Use science know-how to turn a winter wonderland into a tasty treat! email to friend
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1. Fill the plastic jar about half full with snow (or crushed ice).
2. Add about 6 tablespoons of rock salt to the ice. Seal the jar and shake the snow and salt for about five minutes. You’ll need to wear your gloves when you’re handling the bag. If you’re curious as to why you have to wear gloves, measure the temperature of the mixture with a thermometer. The rock salt and ice mixture gets down to about 14 degrees F (-10 degrees C)!
3. Use one quart-size zipper-lock bag to mix the following ingredients:
   • 1/2 cup of half & half
   • 1 tablespoon sugar
   • 1/2 teaspoon vanilla extract
4. Seal tightly, allowing as little air to remain in the bag as possible. Too much air left inside may force the bag open during shaking.
5. Place this bag inside the other quart-size bag, again leaving as little air inside as possible and sealing well. By double-bagging, the risk of salt and snow leaking into the ice cream is minimized.
6. Place the two bags inside the jar with the snow and seal the bag. Wrap the bag in the towel or put your gloves on, and shake, rock, roll and mix that jar! Your ice cream should be ready after about 15-20 minutes.
7. Once mixed, remove the inner bags from the jar and rinse them well with water. You don’t want any salt water accidentally getting into your ice cream.

How does it work?

What does the salt do?

Just like we use salt on icy roads in the winter, salt mixed with ice in this case also causes the ice to melt. When salt comes into contact with ice, the freezing point of the ice is lowered. The lowering of the freezing point depends on the amount of salt added. The more salt added, the lower the temperature will be before the salt- water solution freezes. For example, water will normally freeze at 32 degrees F. A 10% salt solution freezes at 20 degrees F, and a 20% solution freezes at 2 degrees F. When salt is added to the ice (or snow), some of the ice melts because the freezing point is lowered. Always remember that heat must be absorbed by the ice for it to melt. The heat that causes the melting comes from the surroundings (the warmer cream mixture). By lowering the temperature at which ice is frozen, you were able to create an environment in which the cream mixture could freeze at a temperature below 32 degrees F into ice cream.

Additional Info

Did You Know? In 1846, Nancy Johnson invented the hand-cranked ice cream churn and ice cream surged in popularity. Then, in 1904, ice cream cones were invented at the St. Louis World Exposition. An ice cream vendor ran out of dishes and improvised by rolling up some waffles to make cones.