Make ice cream in a bag!
Degree of difficulty: Easy
Time: 5 minutes to assemble ingredients, 5 minutes to shake
1 gallon size locking plastic bag
2 quart size locking plastic bags
4 cups of Ice cubes
6 tablespoons rock salt
1 tablespoon sugar
½ cup milk or half and half
¼ teaspoon vanilla extract
- Combine milk (or half and half), vanilla and sugar into the small bag.
- Remove as much air as possible. Seal.
- Put this bag in a second quart size bag, to reduce chances of leakage.
- Fill large bag half full of ice, and add rock salt.
- Put small bags inside large bag, and seal completely.
- Shake! Mixture will turn to ice cream in about 5 minutes. Wear gloves to keep hands comfy!
Servings: About 1 scoop per bag. Recipe can be doubled for two scoops, but beware – ice can get heavy!
A word about how it works:
Ice has to absorb energy in order to melt. It gets this energy from the heat of sources that surround it, like your hands… and the relatively warm ice cream ingredients. When you add salt to the ice, this lowers the freezing point beyond 32 degrees (a 10% salt solution freezes at 20 degrees F), so even more energy has to be absorbed from the environment in order for the ice to melt. This makes the ice colder than it was before (technically speaking, the salt lowers the melting point), which is how your ice cream freezes.
Question for young experimentalists: What would you get WITHOUT the salt?